linux-kernel - Re: [PATCH v2 4/4] selftests: pci_endpoint: Migrate to Kselftest framework

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Message-ID: <Z0nu8n5GEuZ0zaBD@ryzen>
Date: Fri, 29 Nov 2024 17:42:26 +0100
From: Niklas Cassel <cassel@...nel.org>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: kw@...ux.com, gregkh@...uxfoundation.org, arnd@...db.de,
	lpieralisi@...nel.org, shuah@...nel.org, kishon@...nel.org,
	aman1.gupta@...sung.com, p.rajanbabu@...sung.com,
	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
Subject: Re: [PATCH v2 4/4] selftests: pci_endpoint: Migrate to Kselftest
 framework

On Fri, Nov 29, 2024 at 10:05:55PM +0530, Manivannan Sadhasivam wrote:
> On Fri, Nov 29, 2024 at 02:51:26PM +0100, Niklas Cassel wrote:
> > Hello Mani,
> > 
> > On Fri, Nov 29, 2024 at 02:54:15PM +0530, Manivannan Sadhasivam wrote:
> > > Migrate the PCI endpoint test to Kselftest framework. All the tests that
> > > were part of the previous pcitest.sh file were migrated.
> > > 
> > > Below is the exclusive list of tests:
> > > 
> > > 1. BAR Tests (BAR0 to BAR5)
> > > 2. Legacy IRQ Tests
> > > 3. MSI Interrupt Tests (MSI1 to MSI32)
> > > 4. MSI-X Interrupt Tests (MSI-X1 to MSI-X2048)
> > > 5. Read Tests - MEMCPY (For 1, 1024, 1025, 1024000, 1024001 Bytes)
> > > 6. Write Tests - MEMCPY (For 1, 1024, 1025, 1024000, 1024001 Bytes)
> > > 7. Copy Tests - MEMCPY (For 1, 1024, 1025, 1024000, 1024001 Bytes)
> > > 8. Read Tests - DMA (For 1, 1024, 1025, 1024000, 1024001 Bytes)
> > > 9. Write Tests - DMA (For 1, 1024, 1025, 1024000, 1024001 Bytes)
> > > 10. Copy Tests - DMA (For 1, 1024, 1025, 1024000, 1024001 Bytes)
> > 
> > I'm not sure if it is a great idea to add test case number 10.
> > 
> > While it will work if you use the "dummy memcpy" DMA channel which uses
> > MMIO under the hood, if you actually enable a real DMA controller (which
> > often sets the DMA_PRIVATE cap in the DMA controller driver (e.g. if you
> > are using a DWC based PCIe EP controller and select CONFIG_DW_EDMA=y)),
> > pci_epf_test_copy() will fail with:
> > [   93.779444] pci_epf_test pci_epf_test.0: Cannot transfer data using DMA
> > 
> 
> So the idea is to exercise all the options provided by the epf-test driver. In
> that sense, we need to have the DMA COPY test. However, I do agree that the
> common DMA controllers will fail this case. So how about just simulating the DMA
> COPY for controllers implementing DMA_PRIVATE cap? I don't think it hurts to
> have this feature in test driver.

I guess you could modify pci-epf-test to simply do MMIO in test_copy(),
if USE_DMA && DMA_PRIVATE is set, as you suggest.

We should probably print a warning/info that we are falling back to MMIO
in that case though.


Kind regards,
Niklas