On Sat, Mar 12, 2022 at 11:07:20AM +0530, Manivannan Sadhasivam wrote: > On Fri, Mar 11, 2022 at 10:01:47PM +0300, Serge Semin wrote: > > On Fri, Mar 11, 2022 at 11:11:34PM +0530, Manivannan Sadhasivam wrote: [nip] > > > > > As per my understanding, the eDMA is solely used in the PCIe endpoint. And the > > > access to it happens over PCIe bus or by the local CPU. > > > > Not fully correct. Root Ports can also have eDMA embedded. In that > > case the eDMA can be only accessible from the local CPU. At the same > > time the DW PCIe End-point case is the IP-core synthesize parameters > > specific. It's always possible to access the eDMA CSRs from local > > CPU, but a particular End-point BAR can be pre-synthesize to map > > either Port Logic, or eDMA or iATU CSRs. Thus a PCIe root port can > > perform a full End-point configuration. Anyway the case if the eDMA > > functionality being accessible over the PCIe wire doesn't really make > > much sense with no info regarding the application logic hidden behind > > the PCIe End-point interface since SAR/DAR LLP is supposed to be > > initialized with an address from the local (application) memory space. > > > > Thanks for the explanation, it clarifies my doubt. I got misleaded by the > earlier commits... > > > So AFAICS the main usecase of the controller is 1) - when eDMA is a > > part of the Root Port/End-point and only local CPU is supposed to have > > it accessed and configured. > > > > I can resend this patch with my fix to the problem. What do you think? > > > > Yes, please do. Ok. I'll be AFK today, but will send my patches tomorrow. @Frank, Could you please hold on with respinning the series for a few days? I'll send out some of my patches then with a note which one of them could be picked up by you and merged into this series. -Sergey > > Thanks, > Mani > > > -Sergey > > > > > > > > The commit from Alan Mikhak is what I took as a reference since the patch was > > > already merged: > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/dma/dw-edma?id=bd96f1b2f43a39310cc576bb4faf2ea24317a4c9 > > > > > > Thanks, > > > Mani > > > > > > > -Sergey > > > > > > > > > + * > > > > > + ****************************************************************/ > > > > > + > > > > > > > > > + if ((dir == DMA_DEV_TO_MEM && chan->dir == EDMA_DIR_READ) || > > > > > + (dir == DMA_DEV_TO_MEM && chan->dir == EDMA_DIR_WRITE)) > > > > > + read = true; > > > > > > > > Seeing the driver support only two directions DMA_DEV_TO_MEM/DMA_DEV_TO_MEM > > > > and EDMA_DIR_READ/EDMA_DIR_WRITE, this conditional statement seems > > > > redundant. > > > > > > > > > + > > > > > + /* Program the source and destination addresses for DMA read/write */ > > > > > + if (read) { > > > > > burst->sar = src_addr; > > > > > if (xfer->type == EDMA_XFER_CYCLIC) { > > > > > burst->dar = xfer->xfer.cyclic.paddr; > > > > > -- > > > > > 2.24.0.rc1 > > > > >
