On Mon, May 23, 2022 at 5:18 PM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > > On Mon, May 23, 2022 at 02:19:34PM -0500, Zhi Li wrote: > > > Bjorn: Are you satisfied with the below message? I will fix the > > other code in the next version. > > Looks good, minor questions and tweaks below: > > > Some PCI Endpoint controllers integrate an eDMA (embedded DMA). > > The eDMA controller issues a single bus command per data transfer. > > Still not sure why this sentence is here. Is it something the patch > relies on? Why does it matter how many bus commands there are? Okay, let me remove this line in the next version. > > > eDMA can bypass the outbound memory address translation unit to > > access all RC memory space. > > > > Add eDMA support for pci-epf-test. > > > > EPF test can use, depending on HW availability, eDMA or general system > > DMA controllers to perform DMA. The test probes the EPF DMA channel > > capabilities. > > Depending on HW availability, the EPF test can use either eDMA or > general system DMA controllers to perform DMA. The test tries to use > eDMA first and falls back to general system DMA controllers if > there's no eDMA. > > > Separate dma_chan to dma_chan_tx and dma_chan_rx. Search eDMA channel > > firstly, then search memory to memory DMA channel if eDMA does not exist. > > If general memory to memory channels are used, dma_chan_rx = dma_chan_tx. > > Search for an eDMA channel first, then search for a memory-to-memory > DMA channel ... > > > Add dma_addr_t dma_remote in pci_epf_test_data_transfer() > > because eDMA uses remote RC physical address directly. > > > > Add enum dma_transfer_direction dir in pci_epf_test_data_transfer() > > because eDMA chooses the correct RX/TX channel by dir. > > > > The overall steps are > > > > 1. Execute dma_request_channel() and filter function to find correct > > eDMA RX and TX Channel. If a channel does not exist, fallback to try to > > allocate general memory to memory DMA channel. > > 2. Execute dmaengine_slave_config() to configure remote side physical > > address. > > 3. Execute dmaengine_prep_slave_single() to create transfer descriptor. > > 4. Execute tx_submit(). > > 5. Execute dma_async_issue_pending()
