On Wed, Jan 11, 2023 at 01:42:21PM -0800, Sathyanarayanan Kuppuswamy wrote:
> On 1/11/23 12:31 PM, Vidya Sagar wrote:
> > As the ECRC configuration bits are part of AER registers, configure
> > ECRC only if AER is natively owned by the kernel.
>
> ecrc command line option takes "bios/on/off" as possible options. It
> does not clarify whether "on/off" choices can only be used if AER is
> owned by OS or it can override the ownership of ECRC configuration
> similar to pcie_ports=native option. Maybe that needs to be clarified.
Good point, what do you think of an update like this:
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6cfa6e3996cf..f7b40a439194 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4296,7 +4296,9 @@
specified, e.g., 12@pci:8086:9c22:103c:198f
for 4096-byte alignment.
ecrc= Enable/disable PCIe ECRC (transaction layer
- end-to-end CRC checking).
+ end-to-end CRC checking). Only effective
+ if OS has native AER control (either granted by
+ ACPI _OSC or forced via "pcie_ports=native").
bios: Use BIOS/firmware settings. This is the
the default.
off: Turn ECRC off
I don't know whether the "ecrc=" parameter is really needed. If we
were adding it today, I would ask "why not enable ECRC wherever it is
supported?" If there are devices where it's broken, we could always
add quirks to disable it on a case-by-case basis.
But I think the patch below is the right thing to do for now. Vidya,
did you trip over an issue because of this, e.g., a conflict between
firmware use of AER and Linux use of it? If so, maybe we could
mention a symptom on the commit log. But my guess is you probably
found this by inspection.
Bjorn
> > Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
> > ---
> > drivers/pci/pcie/aer.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> > index e2d8a74f83c3..730b47bdcdef 100644
> > --- a/drivers/pci/pcie/aer.c
> > +++ b/drivers/pci/pcie/aer.c
> > @@ -184,6 +184,9 @@ static int disable_ecrc_checking(struct pci_dev *dev)
> > */
> > void pcie_set_ecrc_checking(struct pci_dev *dev)
> > {
> > + if (!pcie_aer_is_native(dev))
> > + return;
> > +
> > switch (ecrc_policy) {
> > case ECRC_POLICY_DEFAULT:
> > return;
>
> --
> Sathyanarayanan Kuppuswamy
> Linux Kernel Developer
