Hi Andrew, On 07/27/2017 04:38 PM, Andrew Fish wrote:
Brijesh, If you look in the UEFI Spec 13.4 EFI PCI I/O Protocol there is a good write on DMA. DMA Bus Master Read Operation ========================= Call Map() for EfiPciIoOperationBusMasterRead. Program the DMA Bus Master with the DeviceAddress returned by Map(). Start the DMA Bus Master. Wait for DMA Bus Master to complete the read operation. Call Unmap(). DMA Bus Master Write Operation ========================== Call Map() for EfiPciOperationBusMasterWrite. Program the DMA Bus Master with the DeviceAddress returned by Map(). Start the DMA Bus Master. Wait for DMA Bus Master to complete the write operation. Perform a PCI controller specific read transaction to flush all PCI write buffers (See PCI Specification Section 3.2.5.2) . Call Flush(). Call Unmap(). DMA Bus Master Common Buffer Operation ================================== Call AllocateBuffer() to allocate a common buffer. Call Map() for EfiPciIoOperationBusMasterCommonBuffer. Program the DMA Bus Master with the DeviceAddress returned by Map(). The common buffer can now be accessed equally by the processor and the DMA bus master. Call Unmap(). Call FreeBuffer().
Thanks for the link. -Brijesh _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
