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

[Niklas Cassel <cassel@kernel.org>]

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

See:
https://github.com/torvalds/linux/blob/v6.12/drivers/pci/endpoint/functions/pci-epf-test.c#L363-L368


Kind regards,
Niklas