640 lines
24 KiB
Plaintext
640 lines
24 KiB
Plaintext
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Video DMA Interface.
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This note outlines a proposed interface between the display driver,
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miniport and the video port. The objective is to provide an interface
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for the display driver that optimizes DMA throughput for devices that
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support scattergather while maintaining system throughput. The design
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also optimizes locking, performing the DMA and unlocking into one
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IOCTL if desired, a significant performance win. The idea is to provide
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a handle available to the display driver that represents locked memory
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and for that handle to be returned from each DMA IOCTL request. The
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miniport fields some of theses IOCTLs and calls into the video port for
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support.
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This interface supports only PCI busmaster devices.
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///////////////////////////////////////////////////////////////////
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Video port to miniport interface.
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///////////////////////////////////////////////////////////////////
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The miniport must provide 2 things at DriverEntry time:
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A) Set Master in VIDEO_PORT_CONFIG_INFO to TRUE.
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B) Provide a callback HwStartDma() of type PVIDEO_HW_START_DMA
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in the VIDEO_HW_INITIALIZATION_DATA.
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Then the following interfaces can be used:
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The NT video port support now exports to the miniport the following
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function:
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1) BOOLEAN
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VideoPortLockPages(
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IN PVOID HwDeviceExtension,
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IN OUT PVIDEO_REQUEST_PACKET pVrp
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IN OUT PEVENT pMappedUserEvent,
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IN PEVENT pDisplayEvent,
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IN DMA_FLAGS DmaFlags
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);
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This routine can be called by the miniport to do busmaster DMA for
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DMA devices. It returns TRUE if successful and FALSE if not successful.
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It can only be called in the context of an IOCTL. It cannot be called
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from an ISR or DPC.
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Its arguments are:
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1) A pointer to a DEVICE_EXTENSION.
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2) A pointer to a VIDEO_REQUEST_PACKET, whose OutputBuffer it may
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modify. The InputBuffer must be the virtual address of the memory
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to be locked. The InputBufferSize must be the size of that memory.
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The output buffer will receive a PDMA from which may be extracted
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a pointer to a scattergather list of physical pages which comprise
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the locked down virtual address (via GET_VIDEO_SCATTERGATHER). From
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this pointer, one can extract the physical address of any virtual
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address (see GET_VIDEO_PHYSICAL_ADDRESS).
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3) A pointer to a mapped user event, which may be set by the miniport.
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This is either a valid event returned from EngMapEvent or NULL. This
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should be received from the display driver. It will be passed into
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HwStartDma every time the resulting handle from VideoPortLockPages()
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is passed into the Video Port for a DMA operation. All events can only
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be set in the miniport, not waited on.
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4) A pointer to an event received from the display driver, intended
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to be used by the display driver to wait on DMA completion. May be
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NULL. Again, may only be set in miniport.
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This pointer to an event will also be passed into HwStartDma every
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time the resulting handle is passed into the Video Port for a DMA
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operation.
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4) An enum of type DMA_FLAGS defined in video.h. The values can be:
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a) VideoPortUnlockAfterDma
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This value should be used for a "one shot" dma action, where
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the memory is locked and a dma handle passed to HwStartDma(),
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then the memory is unlocked after the miniport signals via
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setting pDmaCompletionEvent.
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b) VideoPortKeepPagesLocked
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This value should only be used for dedicated graphics units.
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It does not guarantee that the virtual memory passed in will
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remain locked after a dma has completed, only that the system
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will try to keep it locked.
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c) VideoPortDmaInitOnly
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A typical initialization value. If used, the InputBuffer must
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contain a pointer to virtual memory. The HwStartDma will not
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be called in this case (see below). The memory will remained
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locked if possible.
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2) PDMA
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VideoPortDoDma(
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IN PVOID HwDeviceExtension,
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IN PDMA pDma,
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IN DMA_FLAGS DmaFlags
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);
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Routine Description:
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This function is called by the miniport when a it has a valid DMA
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handle to cause HwStartDma to be called. It can be called outside
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the context of an IOCTL, but not from an ISR. It must execute at
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irql <= DISPATCH_LEVEL.
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Arguments:
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HwDeviceExtension - Pointer to miniport HWDeviceExtension.
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pDma - Non - NULL DMA handle returned by this routine or
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VideoPortLockPages() in OutputBuffer.
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DmaFlags - Flags specifying desired action.
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Return Value:
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Non NULL pDma if the corresponding memory is still locked, NULL
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otherwise.
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3) PVOID
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VideoPortGetCommonBuffer(
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IN PVOID HwDeviceExtension,
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IN ULONG DesiredLength,
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IN ULONG Alignment,
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OUT PVOID * pVirtualAddress,
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OUT PPHYSICAL_ADDRESS pLogicalAddress,
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OUT PULONG pActualLength,
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IN BOOLEAN CacheEnabled
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);
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Routine Description:
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Provides physical address visible to both device and system. Memory seen as contiguous
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by device. This routine can only be reliably called at driver load time. Memory allocated
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must be less than 256K.
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Arguments:
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HwDeviceExtension - device extension available to miniport.
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DesiredLength - size of desired memory (should be minimal).
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Alignment - Desired liagnment of buffer, currently unused.
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pVirtualAddress - unused.
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pLogicalAddress - [out] parameter which will hold physical address of
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of the buffer upon function return.
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pActualLength - Actual length of buffer.
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CacheEnabled - Specifies whether the allocated memory can be cached.
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Return Value:
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Virtual address of the common buffer.
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4) PDMA
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VideoPortGetMdl(
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PVOID HwDeviceExtension,
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PDMA pDma
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);
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Routine Description:
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Returns a PMDL representing the page table of the locked buffer.
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Arguments:
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HwDeviceExtension - device extension available to miniport.
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pDma - Dma handle received from either VideoPortLockPages()
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or VideoPortDoDma().
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Return Value:
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A PMDL reprsenting the locked buffer.
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5) BOOLEAN
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VideoPortSignalDmaComplete(
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IN PVOID HwDeviceExtension,
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IN PVOID pDmaHandle
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)
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/*++
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Routine Description:
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Arguments:
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HwDeviceExtension - a pointer to the miniport HW_DEVICE_EXTENSION.
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pDmaHandle - the handle returned in the output buffer of the
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VIDEO_REQUEST_PACKET after VideoPortLockPages() returns.
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Return Value:
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TRUE if the DPC was scheduled, FALSE otherwise.
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--*/
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6) PVOID
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VideoPortGetDmaContext(
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IN PVOID HwDeviceExtension,
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IN PDMA pDma
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);
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/*++
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Routine Description:
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Arguments:
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HwDeviceExtension - a pointer to the miniport HW_DEVICE_EXTENSION.
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pDma - the handle returned in the output buffer of the
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VIDEO_REQUEST_PACKET after VideoPortLockPages() returns.
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Return Value:
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The Context previously associated with this PDMA.
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--*/
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7) VOID
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VideoPortSetDmaContext(
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IN PVOID HwDeviceExtension,
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OUT PDMA pDma,
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IN PVOID InstanceContext
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);
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/*++
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Routine Description:
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Arguments:
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HwDeviceExtension - a pointer to the miniport HW_DEVICE_EXTENSION.
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pDma - the handle returned in the output buffer of the
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VIDEO_REQUEST_PACKET after VideoPortLockPages() returns.
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InstanceContext - any PVOID supplied by user.
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Return Value:
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NONE.
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--*/
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8) ULONG
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VideoPortGetBytesUsed(
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IN PVOID HwDeviceExtension,
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IN PDMA pDma
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);
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/*++
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Routine Description:
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Arguments:
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HwDeviceExtension - a pointer to the miniport HW_DEVICE_EXTENSION.
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pDma - the handle returned in the output buffer of the
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VIDEO_REQUEST_PACKET after VideoPortLockPages() returns.
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Return Value:
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The number of bytes used in the buffer associated with this PDMA
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--*/
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9) VOID
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VideoPortSetBytesUsed(
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IN PVOID HwDeviceExtension,
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IN OUT PDMA pDma,
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IN ULONG BytesUsed
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);
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/*++
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Routine Description:
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Arguments:
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HwDeviceExtension - a pointer to the miniport HW_DEVICE_EXTENSION.
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pDma - the handle returned in the output buffer of the
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VIDEO_REQUEST_PACKET after VideoPortLockPages() returns.
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BytesUsed - The number of bytes written to the buffer.
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Return Value:
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NONE.
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--*/
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///////////////////////////////////////////////////////////////////
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Display driver to miniport interface (IOCTL interface).
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///////////////////////////////////////////////////////////////////
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1) Miniport IOCTL routine.
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The design attemps to optimize DMA transfer from a fixed piece of virtual
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memory. These IOCTLs are to be defined by the miniport and the following
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descriptions of the IOCTLs are only suggestions.
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IOCTL_VIDEO_DMA_INIT - set by DispDrvr
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Causes VideoPortLockPages() to be called by the miniport where the DMA_FLAGS is
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set to VideoPortDmaInitOnly. This should only be done in graphics dedicated
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contexts, where disk and network IO is secondary to video IO. Driver writers
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must be aware that system performance (e.g. WinBench) can be damaged by leaving
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memory locked.
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IOCTL_VIDEO_DMA_TRANSFER_KEEP_LOCKED - set by DispDrvr
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The miniport may set up this IOCTL such that VideoPortDoDma() is called with the
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VideoPortKeepPagesLocked DMA_FLAGS argument. This scenario is oriented to graphics
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dedicated applications. It optimizes throughput so that the HwStartDma() routine
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in the miniport is called. In this way, DMA operations are optimized such that
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memory resources to other parts of the system are constrained.
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The scatter gather list available to HwStartDma() is valid:
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a) before the routine HwStartDma() returns.
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b) if HwStartDma() returns asynchronously, the list may be valid
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if the system memory manager is not stressed. If the PEVENT
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which is the fourth argument to HwStartDma() is set when the DMA is
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done, it will remain valid until then. If the PEVENT is not set,
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the list may become invalid at random times. This PEVENT must
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be set by :
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VideoPortSetEvent(HwDeviceExtension, PEVENT);
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c) if HwStartDma returns synchronously and the system memory
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manager is not stressed, the list will remain valid. if HwStartDma()
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return synchronously and the memory manager is stressed, the list
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will become invalid after HwStartDma returns.
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IOCTL_VIDEO_DMA_TRANSFER_ONCE - set by DispDrvr
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The miniport may set up this IOCTL so that VideoPortLockPages() is called with
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the VideoPortUnlockAfterDma DMA_FLAGS. This allows the buffer to be locked down,
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the HwStartDma miniport routine to be called back and the memory to be unlocked
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after the dma transfer has completed. This IOCTL is tuned for systems in which
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disk and network IO is very important and memory may be at a premium.
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The same remarks apply to the scatter gather list as for
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IOCTL_VIDEO_TRANSFER_KEEP_LOCKED.
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IOCTL_VIDEO_DMA_UNLOCK_PAGES - set by DispDrvr
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The miniport should simply call VideoPortUnlockPages() with the appropriate
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PDMA.
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Locking memory
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The video port must lock down the memory in order to perform dma. The
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amount of memory locked down is restricted by three things:
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1) Maximal number of physical page breaks supported by the driver.
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This is strictly a function of the dma hardware.
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2) The number of map registers the system has available at
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initialization. This is usually not bounded for busmaster devices,
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except by that indicated by HalGetAdapter().
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3) System performance contraints. In order to provide reasonable
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throughput for other parts of the system, the amount of memory the
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video port allows to be locked down is currently set as follows:
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a) small systems (12-16 meg) 256k
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b) medium systems (16-31 meg) 512k
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c) large systems (>32 meg) 1M
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These default values can be overridden by setting MaxDmaSize value under the
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Devicexxx key in the CurrentControlSet in the registry. Again, drivers which
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leave more than these amounts of memory locked down can severely impact system
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performance.
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Examples:
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from a miniport StartIo routine (note that the display driver formatting
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is unique to the display driver):
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case IOCTL_VIDEO_DMA_INIT:
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{
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//
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// This IOCTL should only be used for buffers that may remained locked
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// down for more than one dma transfer.
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//
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//
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// Map display driver representation into video port. Display
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// driver input buffer is of form
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//
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// typedef struct _DMA_CONTROL
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// {
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// void * pBitmap; // Pointer to memory
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// // to be locked.
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// ULONG ulSize; // size of memory to
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// // be locked.
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// PVOID pDma; // Dma handle [OUT].
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|
|
// PVOID * pPhysAddr; // Location to put
|
||
|
|
// // Physaddr.
|
||
|
|
// PEVENT pDisplayEvent // PEVENT.
|
||
|
|
// PEVENT pMappedUserEvent// Mapped User Mode EVENT
|
||
|
|
// // handle.
|
||
|
|
// } DMA_CONTROL, *PDMA_CONTROL;
|
||
|
|
//
|
||
|
|
//
|
||
|
|
//
|
||
|
|
//
|
||
|
|
|
||
|
|
PDMA_CONTROL pDmaCtrl = (PDMA_CONTROL) RequestPacket->InputBuffer;
|
||
|
|
PUCHAR ptmp = pDmaCrtl->bitmap;
|
||
|
|
ULONG size = pDmaCrtl->size;
|
||
|
|
|
||
|
|
VideoDebugPrint(( 0,"\t InputBuffer:%x\n", ptmp));
|
||
|
|
VideoDebugPrint(( 0,"\t InputBufferLength:%x\n", size));
|
||
|
|
|
||
|
|
//
|
||
|
|
// Save the location to put physaddr.
|
||
|
|
//
|
||
|
|
|
||
|
|
busAddress = (PULONG)(pDmaCtrl->pPhysAddr);
|
||
|
|
|
||
|
|
RequestPacket->InputBuffer = ptmp;
|
||
|
|
RequestPacket->InputBufferLength = size;
|
||
|
|
|
||
|
|
if (RequestPacket->OutputBufferLength <
|
||
|
|
(RequestPacket->StatusBlock->Information =
|
||
|
|
sizeof(ULONG) )) {
|
||
|
|
|
||
|
|
VideoDebugPrint((0, "IOCTL_VIDEO_DMA_INIT error1\n"));
|
||
|
|
status = ERROR_INSUFFICIENT_BUFFER;
|
||
|
|
break;
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
if (!VideoPortLockPages(HwDeviceExtension,
|
||
|
|
RequestPacket,
|
||
|
|
pMappedUserEvent,
|
||
|
|
pDisplayEvent,
|
||
|
|
VideoPortDmaInitOnly))
|
||
|
|
{
|
||
|
|
RequestPacket->StatusBlock->Information = 0;
|
||
|
|
VideoDebugPrint((0, "IOCTL_VIDEO_DMA_INIT error2\n"));
|
||
|
|
status = ERROR_INSUFFICIENT_BUFFER;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
//
|
||
|
|
// Have to extract Physical address from scatterlist via DMA context in
|
||
|
|
// OutputBuffer and put it back into OutputBuffer.
|
||
|
|
//
|
||
|
|
PVOID * ppDmaHandle = (PVOID *)(RequestPacket->OutputBuffer);
|
||
|
|
PVRB_SG pSG = GET_VIDEO_SCATTERGATHER((PULONG)ppDmaHandle);
|
||
|
|
ULONG physaddr;
|
||
|
|
|
||
|
|
pDmaCrtl->DmaHandle = *ppDmaHandle;
|
||
|
|
|
||
|
|
hwDeviceExtension->IoBufferSize = size;
|
||
|
|
hwDeviceExtension->IoBuffer = ptmp;
|
||
|
|
|
||
|
|
GET_VIDEO_PHYSICAL_ADDRESS(pSG, ptmp, ptmp, &size, physaddr);
|
||
|
|
|
||
|
|
*busAddress = physaddr;
|
||
|
|
|
||
|
|
status = NO_ERROR;
|
||
|
|
|
||
|
|
}
|
||
|
|
|
||
|
|
break;
|
||
|
|
}
|
||
|
|
|
||
|
|
case IOCTL_VIDEO_DMA_TRANSFER:
|
||
|
|
//
|
||
|
|
// This IOCTL is optimized so that the display driver can get a buffer locked,
|
||
|
|
// dmaed and unlocked in one IOCTL.
|
||
|
|
//
|
||
|
|
{
|
||
|
|
PDSP_DMA_ARGS pDSPDmaArgs = (PDSP_DMA_ARGS)RequestPacket->InputBuffer;
|
||
|
|
PDSP_DMA pDSPDma = pDSPDmaArgs->pDmaControl;
|
||
|
|
PUCHAR ptmp = pDSPDma ->bitmap;
|
||
|
|
ULONG size = pDSPDma ->size;
|
||
|
|
|
||
|
|
if (RequestPacket->InputBufferLength < sizeof(DSP_DMA_ARGS)) {
|
||
|
|
VideoDebugPrint(( 2,"\n Insufficient Buffer" ));
|
||
|
|
status = ERROR_INSUFFICIENT_BUFFER;
|
||
|
|
break;
|
||
|
|
}
|
||
|
|
|
||
|
|
RequestPacket->InputBuffer = ptmp;
|
||
|
|
RequestPacket->InputBufferLength = size;
|
||
|
|
|
||
|
|
ASSERT(pDSPDma);
|
||
|
|
|
||
|
|
if (RequestPacket->OutputBufferLength <
|
||
|
|
(RequestPacket->StatusBlock->Information =
|
||
|
|
sizeof(ULONG) )) {
|
||
|
|
|
||
|
|
VideoDebugPrint((0, "IOCTL_VIDEO_DMA_INIT error1\n"));
|
||
|
|
status = ERROR_INSUFFICIENT_BUFFER;
|
||
|
|
break;
|
||
|
|
}
|
||
|
|
|
||
|
|
hwDeviceExtension->pDSPDmaArgs = pDSPDmaArgs;
|
||
|
|
|
||
|
|
if (!VideoPortLockPages(HwDeviceExtension,
|
||
|
|
RequestPacket,
|
||
|
|
pDSPDma->pMappedUserEvent,
|
||
|
|
pDSPDma->pDisplayEvent,
|
||
|
|
VideoPortUnlockAfterDma))
|
||
|
|
{
|
||
|
|
RequestPacket->StatusBlock->Information = 0;
|
||
|
|
VideoDebugPrint((0, "IOCTL_VIDEO_DMA_TRANSFER error\n"));
|
||
|
|
status = ERROR_INSUFFICIENT_BUFFER;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
status = NO_ERROR;
|
||
|
|
|
||
|
|
break;
|
||
|
|
|
||
|
|
}
|
||
|
|
|
||
|
|
case IOCTL_VIDEO_DMA_UNLOCK:
|
||
|
|
{
|
||
|
|
//
|
||
|
|
// Private cleanup code. The memory has already been unlocked.
|
||
|
|
// The InputBuffer contains the Dma Handle.
|
||
|
|
//
|
||
|
|
|
||
|
|
PDMA pDma = *(PDMA*) (RequestPacket->InputBuffer);
|
||
|
|
|
||
|
|
VideoPortUnlockPages(HwDeviceExtension, pDma);
|
||
|
|
|
||
|
|
break;
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
2) Display driver code.
|
||
|
|
|
||
|
|
DISPDBG((1, "Target, DmaControl.pBitmap:%x, DmaControl.ulSize:%x\n", DmaControl.pBitmap, DmaControl.ulSize));
|
||
|
|
|
||
|
|
//
|
||
|
|
// Ask the miniport to lock the pages needed for this DMA, do the dma and unlock them.
|
||
|
|
//
|
||
|
|
|
||
|
|
DSPDmaArgs.pDma = (PVOID)DmaHandle;
|
||
|
|
DSPDmaArgs.DmaBase = ptrgBase;
|
||
|
|
DSPDmaArgs.WidthTrg = widthTrg;
|
||
|
|
DSPDmaArgs.WidthSrc = widthSrc;
|
||
|
|
DSPDmaArgs.width__ = width * DSPSRCPIXELBYTES;
|
||
|
|
DSPDmaArgs.Height = height;
|
||
|
|
DSPDmaArgs.Offset = ulOffset;
|
||
|
|
DSPDmaArgs.pPhysAddr = pPCIAddress;
|
||
|
|
DSPDmaArgs.bitdepth = DSPSRCPIXELBITS;
|
||
|
|
DSPDmaArgs.HS = TRUE;
|
||
|
|
DSPDmaArgs.pDmaControl = &DmaControl;
|
||
|
|
|
||
|
|
if (EngDeviceIoControl(ppdev->hDriver,
|
||
|
|
IOCTL_VIDEO_DMA_TRANSFER,
|
||
|
|
&DSPDmaArgs,
|
||
|
|
sizeof(DSPDmaArgs),
|
||
|
|
&(DSPDmaArgs.pDma),
|
||
|
|
sizeof(DSPDmaArgs.pDma),
|
||
|
|
&returnedDataLength))
|
||
|
|
{
|
||
|
|
DISPDBG((0, "DSP.DLL!MSDMA - EngDeviceIoControl IOCTL_VIDEO_DMA_TRANSFER Error!!!\n"));
|
||
|
|
DISPDBG((0, "DSP.DLL!vBitbltHSDMA - Exit\n"));
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
The requirements for these interfaces include:
|
||
|
|
|
||
|
|
1) In the PVIDEO_HW_INITIALIZATION_DATA, the following fields need to be filled:
|
||
|
|
|
||
|
|
PVIDEO_HW_START_DMA HwStartDma - a pointer to a function which can be
|
||
|
|
called when page locking is complete. This function returns
|
||
|
|
Dma_Async_Return if it returns before the transfer is complete or
|
||
|
|
Dma_Sync_Return if it returns after the transfer is complete.
|
||
|
|
These return values are typedefed in video.h. This function takes
|
||
|
|
as arguments:
|
||
|
|
a) pHwDeviceExtension - a pointer to a miniport device
|
||
|
|
extension.
|
||
|
|
b) a dma handle returned from a IOCTL_VIDEO_DMA_INIT or
|
||
|
|
IOCTL_VIDEO_DMA_TRANSFER call.
|
||
|
|
c) a PEVENT which is the user Event mapped into kernel mode.
|
||
|
|
(NULL if pMappedUserEvent is NULL).
|
||
|
|
d) pDisplayEvent - a PEVENT, intended to be created and
|
||
|
|
waited on by the DisplayDriver and set by the miniport.
|
||
|
|
e) another PEVENT which must be set if the routine returns
|
||
|
|
Dma_Async_Return when the DMA completes. Failure to set
|
||
|
|
this PEVENT may invalidate the scatter gather lists at
|
||
|
|
any time. It must be set by:
|
||
|
|
|
||
|
|
VideoPortSetEvent(HwDeviceExtension, pVPEvent);
|
||
|
|
|
||
|
|
Also, HwDeviceExtension should make a copy of the elements of the
|
||
|
|
irp it intends to use or pass on, as the irp will be completed when
|
||
|
|
HwStartDma returns, and hence it's fields will be invalidated.
|
||
|
|
|
||
|
|
|
||
|
|
2) In the PORT_CONFIG_INFO, the following fields need to be
|
||
|
|
filled:
|
||
|
|
|
||
|
|
ULONG DmaChannel - a value indicating if the device supports
|
||
|
|
DMA.
|
||
|
|
|
||
|
|
ULONG DmaPort - a value indicating if the device supports
|
||
|
|
microchannel DMA.
|
||
|
|
|
||
|
|
ULONG NumberOfPhysicalBreaks - a value indicating the
|
||
|
|
maximal number of physical breaks the device supports.
|
||
|
|
|
||
|
|
DMA_WIDTH DmaWidth - a value indicating the width of the dma
|
||
|
|
device.
|
||
|
|
|
||
|
|
DMA_SPEED DmaSpeed - a value indicating the specified transfer
|
||
|
|
speed.
|
||
|
|
|
||
|
|
BOOLEAN DemandMode - a BOOLEAN indicating that the device can
|
||
|
|
be programmed for demand mode rather than single cycle operations.
|
||
|
|
|
||
|
|
BOOLEAN bMapBuffers- a BOOLEAN indicating if an adapter
|
||
|
|
requires that the data buffers be mapped into virtual address space.
|
||
|
|
|
||
|
|
BOOLEAN NeedPhysicalAddresses - a BOOLEAN indicating that the
|
||
|
|
driver will need to translate virtual to physical addresses.
|
||
|
|
|
||
|
|
BOOLEAN ScatterGather - a BOOLEAN indicating that the
|
||
|
|
driver will support scatter gather.
|
||
|
|
|
||
|
|
BOOLEAN Master - a BOOLEAN indicating that the adapter
|
||
|
|
is a bus master. Again, currently required to be TRUE.
|
||
|
|
|
||
|
|
ULONG MaximumScatterGatherChunkSize - the largest contiguous
|
||
|
|
piece of memory the dma controller can handle. This value is zero
|
||
|
|
if and only if the size is unbounded.
|