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

Jonathan Cameron
2024-12-13T15:55:00Z

On Thu, 12 Dec 2024 20:48:38 +0200 (EET)
Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:

> 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.
>
Ah. I should read that series ;)

Absolutely fine - sometime generic naming is the best we can do!

Jonathan