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

[Niklas Cassel <cassel@kernel.org>]

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.
> 
> 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@synopsys.com/

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.


2)
https://github.com/rockchip-linux/kernel/blob/develop-6.1/drivers/pci/controller/dwc/pcie-dw-dmatest.c
https://github.com/rockchip-linux/kernel/blob/develop-6.1/drivers/pci/controller/rockchip-pcie-dma.h


Anyway, since Vinod is the maintainer, it is probably him you need to talk
to come up with a way forward. To not waste your time, I would talk to him
before you spend a lot of time implementing something :)


Kind regards,
Niklas