Re: [PATCH v6 6/8] PCI: Add TLP Prefix reading into pcie_read_tlp_log()

Ilpo Järvinen
2024-12-12T18:48:47Z

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On Thu, 12 Dec 2024, Ilpo Järvinen wrote:

> On Wed, 11 Dec 2024, Jonathan Cameron wrote:
>
> > On Fri, 13 Sep 2024 17:36:30 +0300
> > Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:
> >
> > > pcie_read_tlp_log() handles only 4 Header Log DWORDs but TLP Prefix Log
> > > (PCIe r6.1 secs 7.8.4.12 & 7.9.14.13) may also be present.
> > >
> > > Generalize pcie_read_tlp_log() and struct pcie_tlp_log to handle also
> > > TLP Prefix Log. The relevant registers are formatted identically in AER
> > > and DPC Capability, but has these variations:
> > >
> > > a) The offsets of TLP Prefix Log registers vary.
> > > b) DPC RP PIO TLP Prefix Log register can be < 4 DWORDs.
> > >
> > > Therefore callers must pass the offset of the TLP Prefix Log register
> > > and the entire length to pcie_read_tlp_log() to be able to read the
> > > correct number of TLP Prefix DWORDs from the correct offset.
> > >
> > > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> >
> > Trivial comments below
> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> >
> > Would have been nice if they'd just made the formats have the
> > same sized holes etc!
>
> That's not even the worst problem.
>
> They managed to copy-paste most of the stuff into DPC (copy-paste is
> really obvious because the text still refers to AER in a DPC section :-))
> but forgot to add a few capability fields into the DPC capability, most
> importantly, the bit that indicates whether TLP was logged in Flit mode
> or not And now we get to keep the pieces how to interpret the Log
> Registers (relates to the follow up series). :-(
>
> > > diff --git a/drivers/pci/pcie/tlp.c b/drivers/pci/pcie/tlp.c
> > > index 65ac7b5d8a87..def9dd7b73e8 100644
> > > --- a/drivers/pci/pcie/tlp.c
> > > +++ b/drivers/pci/pcie/tlp.c
> > > @@ -11,26 +11,65 @@
> >
> > > /**
> > > * pcie_read_tlp_log - read TLP Header Log
> > Maybe update this to read TLP Header and Prefix Logs
> > > * @dev: PCIe device
> > > * @where: PCI Config offset of TLP Header Log
> > > + * @where2: PCI Config offset of TLP Prefix Log
> >
> > Is it worth giving it a more specific name than where2?
> > Possibly renaming where as well!
>
> Sure, why not.

Hi again,

After doing this rename, I rebased the Flit mode series on top of it and
realized there's one small problem with naming where2. It will be
overloaded between TLP Prefix Log (Non-Flit mode) and extended TLP Header
Log (DW5+) (Flit mode) so I'm not sure if there's really going to be a
good name for it.

--
i.