Re: [PATCH 00/17] dmaengine: dw-edma: Support dynamic LL appends

[Koichiro Den]

On Tue, Jun 30, 2026 at 01:38:32PM +0200, Manivannan Sadhasivam wrote:
> On Mon, Jun 22, 2026 at 04:18:01PM +0200, Niklas Cassel wrote:
> > On Mon, Jun 22, 2026 at 04:38:49PM +0900, Koichiro Den wrote:
> > > On Tue, Jun 16, 2026 at 12:40:54AM +0900, Koichiro Den wrote:
> > > 
> > > Hi Frank, Niklas, all,
> > > 
> > > I am looking for a good way to stress PCIe controller DMA engines, such as
> > > eDMA/HDMA, and measure their upper-bound throughput.
> > > 
> > > nvmet_pci_epf is useful since it is a real in-tree consumer, but it is not a
> > > very direct benchmark for the DMA engine itself. So I wonder if
> > > pci_endpoint_test would be a reasonable place to add an opt-in DMA performance
> > > mode.
> > > 
> 
> I think including DMA performance tests to pci-epf-test would overload it.
> pci-epf-test already provides the bare minimum read/write benchmark, which I
> feel is sufficient enough.

Understood, thank you for sharing your thoughts.

> 
> > > One possible option I have in mind is:
> > > 
> > >   - a new fixture, pci_ep_dma_perf
> > >   - opt-in execution, for example with PCITEST_PERF=1 environment variable
> > >   - a few variants such as single and sg, possibly with a few knobs:
> > >      - PCITEST_PERF_NUM_WORKERS, to use multiple EP-side workers
> > >      - PCITEST_PERF_NUM_CHANS, to use multiple DMA channels
> > >      - perhaps other knobs for SG entry size, number of entries, etc.
> > >   - the new tests: READ_PERF_TEST and WRITE_PERF_TEST
> > > 
> > > For the other possible places I could think of, this still seems to fit best in
> > > pci_endpoint_test. For example, extending dmatest does not seem to fit well
> > > because this needs both EP and RC side setup. A separate kselftest also feels
> > > like it would duplicate a lot of pci_endpoint_test code. That said, I might be
> > > missing something.
> > > 
> > > What do you think? Any thoughts or suggestions would be much appreciated.
> > 
> > There are two existing (out-of-tree) tests for eDMA that I know of:
> > 
> > 1)
> > https://patchwork.kernel.org/project/linux-pci/patch/cc195ac53839b318764c8f6502002cd6d933a923.1547230339.git.gustavo.pimentel@xxxxxxxxxxxx/
> > 
> > But as you can see, the comment was to use dmatest instead.
> > AFAICT, dmatest currently only supports DMA_MEMCPY, which, by hardware design,
> > cannot be supported by DWC eDMA HW (since it only allows remote to local, or
> > local to remote, and remote has to be a PCI address, while local is local
> > physical address).
> > 
> > Perhaps it is possible to add DMA_SLAVE support to dmatest.
> > 
> 
> Since Vinod is not in favor of it, you can also think about adding eDMA/HDMA
> specific kselftests. It makes lot of sense to write a  standalone test since
> we can configure this IP from both host and endpoint side.

Alright, I'll consider eDMA/HDMA-specific kselftests once the need becomes
clearer.

Mani, Vinod, thank you for the comments.

Best regards,
Koichiro

> 
> - Mani
> 
> -- 
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