Hi Vinod, On 31/05/19 10:37 AM, Vinod Koul wrote: > Hi Kishon, > > On 30-05-19, 11:16, Kishon Vijay Abraham I wrote: >> +Vinod Koul >> >> Hi, >> >> On 30/05/19 4:07 AM, Alan Mikhak wrote: >>> On Mon, May 27, 2019 at 2:09 AM Gustavo Pimentel >>> <Gustavo.Pimentel@xxxxxxxxxxxx> wrote: >>>> >>>> On Fri, May 24, 2019 at 20:42:43, Alan Mikhak <alan.mikhak@xxxxxxxxxx> >>>> wrote: >>>> >>>> Hi Alan, >>>> >>>>> On Fri, May 24, 2019 at 1:59 AM Gustavo Pimentel >>>>> <Gustavo.Pimentel@xxxxxxxxxxxx> wrote: >>>>>> >>>>>> Hi Alan, >>>>>> >>>>>> This patch implementation is very HW implementation dependent and >>>>>> requires the DMA to exposed through PCIe BARs, which aren't always the >>>>>> case. Besides, you are defining some control bits on >>>>>> include/linux/pci-epc.h that may not have any meaning to other types of >>>>>> DMA. >>>>>> >>>>>> I don't think this was what Kishon had in mind when he developed the >>>>>> pcitest, but let see what Kishon was to say about it. >>>>>> >>>>>> I've developed a DMA driver for DWC PCI using Linux Kernel DMAengine API >>>>>> and which I submitted some days ago. >>>>>> By having a DMA driver which implemented using DMAengine API, means the >>>>>> pcitest can use the DMAengine client API, which will be completely >>>>>> generic to any other DMA implementation. >> >> right, my initial thought process was to use only dmaengine APIs in >> pci-epf-test so that the system DMA or DMA within the PCIe controller can be >> used transparently. But can we register DMA within the PCIe controller to the >> DMA subsystem? AFAIK only system DMA should register with the DMA subsystem. >> (ADMA in SDHCI doesn't use dmaengine). Vinod Koul can confirm. > > So would this DMA be dedicated for PCI and all PCI devices on the bus? Yes, this DMA will be used only by PCI ($patch is w.r.t PCIe device mode. So all endpoint functions both physical and virtual functions will use the DMA in the controller). > If so I do not see a reason why this cannot be using dmaengine. The use Thanks for clarifying. I was under the impression any DMA within a peripheral controller shouldn't use DMAengine. > case would be memcpy for DMA right or mem to device (vice versa) transfers? The device is memory mapped so it would be only memcopy. > > Btw many driver in sdhci do use dmaengine APIs and yes we are missing > support in framework than individual drivers I think dmaengine APIs is used only when the platform uses system DMA and not ADMA within the SDHCI controller. IOW there is no dma_async_device_register() to register ADMA in SDHCI with DMA subsystem. Thanks Kishon
