linux-kernel - Re: [PATCH v4 3/3] selftests: pci_endpoint: Migrate to Kselftest framework

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Message-ID: <20250102070404.aempesitsqktfnle@thinkpad>
Date: Thu, 2 Jan 2025 12:34:04 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Niklas Cassel <cassel@...nel.org>
Cc: kw@...ux.com, gregkh@...uxfoundation.org, arnd@...db.de,
	lpieralisi@...nel.org, shuah@...nel.org, kishon@...nel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	bhelgaas@...gle.com, linux-arm-msm@...r.kernel.org, robh@...nel.org,
	linux-kselftest@...r.kernel.org,
	Aman Gupta <aman1.gupta@...sung.com>,
	Padmanabhan Rajanbabu <p.rajanbabu@...sung.com>
Subject: Re: [PATCH v4 3/3] selftests: pci_endpoint: Migrate to Kselftest
 framework

On Tue, Dec 31, 2024 at 08:33:57PM +0100, Niklas Cassel wrote:
> 
> 
> On 31 December 2024 20:18:12 CET, Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org> wrote:
> >On Tue, Dec 31, 2024 at 06:42:42PM +0100, Niklas Cassel wrote:
> >> On Tue, Dec 31, 2024 at 06:43:41PM +0530, Manivannan Sadhasivam wrote:
> >> 
> >> (...)
> >> 
> >> > +	#  RUN           pci_ep_data_transfer.dma.COPY_TEST ...
> >> > +	#            OK  pci_ep_data_transfer.dma.COPY_TEST
> >> > +	ok 11 pci_ep_data_transfer.dma.COPY_TEST
> >> > +	# PASSED: 11 / 11 tests passed.
> >> > +	# Totals: pass:11 fail:0 xfail:0 xpass:0 skip:0 error:0
> >> > +
> >> > +
> >> > +Testcase 11 (pci_ep_data_transfer.dma.COPY_TEST) will fail for most of the DMA
> >> > +capable endpoint controllers due to the absence of the MEMCPY over DMA. For such
> >> > +controllers, it is advisable to skip the forementioned testcase using below
> >> > +command::
> >> 
> >> Hm.. this is strictly not correct. If will currently fail because pci-epf-test.c
> >> does:
> >> if ((reg->flags & FLAG_USE_DMA) && epf_test->dma_private)
> >> 	return -EINVAL;
> >> 
> >> So even if a DMA driver has support for the DMA_MEMCPY cap, if the DMA driver
> >> also has the DMA_PRIVATE cap, this test will fail because of the code in
> >> pci-epf-test.c.
> >> 
> >
> >Right. But I think the condition should be changed to test for the MEMCPY
> >capability instead. Like,
> >
> >diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> >index ef6677f34116..0b211d60a85b 100644
> >--- a/drivers/pci/endpoint/functions/pci-epf-test.c
> >+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> >@@ -328,7 +328,7 @@ static void pci_epf_test_copy(struct pci_epf_test *epf_test,
> >        void *copy_buf = NULL, *buf;
> > 
> >        if (reg->flags & FLAG_USE_DMA) {
> >-               if (epf_test->dma_private) {
> >+               if (!dma_has_cap(DMA_MEMCPY, epf_test->dma_chan_tx->device->cap_mask)) {
> >                        dev_err(dev, "Cannot transfer data using DMA\n");
> >                        ret = -EINVAL;
> >                        goto set_status;
> >
> 
> That check does seem to make more sense than the code that is currently there.
> (Perhaps send this as a proper patch?)

Will do.

> Note that I'm not an expert at dmaengine.
> 
> I have some patches that adds DMA_MEMCPY to dw-edma, but I'm not sure if the DWC eDMA hardware supports having both src and dst as PCI addresses, or if only one of them can be a PCI address (with the other one being a local address).
> 
> If only one of them can be a PCI address, then I'm not sure if your suggested patch is correct.
> 

I don't see why that would be an issue. DMA_MEMCPY is independent of PCI/local
addresses. If a dmaengine driver support doing MEMCPY, then the dma cap should
be sufficient. As you said, if a controller supports both SLAVE and MEMCPY, the
test currently errors out, which is wrong.

- Mani

-- 
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