Re: [PATCH v2 14/24] PCI: rcar: Remove redundant error fabrication when device read fails

[Geert Uytterhoeven]

Hi Naveen,

On Mon, Oct 18, 2021 at 1:52 PM Naveen Naidu <naveennaidu479@xxxxxxxxx> wrote:
> On 18/10, Geert Uytterhoeven wrote:
> > On Sat, Oct 16, 2021 at 5:33 PM Naveen Naidu <naveennaidu479@xxxxxxxxx> wrote:
> > > An MMIO read from a PCI device that doesn't exist or doesn't respond
> > > causes a PCI error. There's no real data to return to satisfy the
> > > CPU read, so most hardware fabricates ~0 data.
> > >
> > > The host controller drivers sets the error response values (~0) and
> > > returns an error when faulty hardware read occurs. But the error
> > > response value (~0) is already being set in PCI_OP_READ and
> > > PCI_USER_READ_CONFIG whenever a read by host controller driver fails.
> > >
> > > Thus, it's no longer necessary for the host controller drivers to
> > > fabricate any error response.
> > >
> > > This helps unify PCI error response checking and make error check
> > > consistent and easier to find.
> > >
> > > Signed-off-by: Naveen Naidu <naveennaidu479@xxxxxxxxx>
> >
> > Thanks for your patch!
> >
> > > --- a/drivers/pci/controller/pcie-rcar-host.c
> > > +++ b/drivers/pci/controller/pcie-rcar-host.c
> > > @@ -161,10 +161,8 @@ static int rcar_pcie_read_conf(struct pci_bus *bus, unsigned int devfn,
> > >
> > >         ret = rcar_pcie_config_access(host, RCAR_PCI_ACCESS_READ,
> > >                                       bus, devfn, where, val);
> > > -       if (ret != PCIBIOS_SUCCESSFUL) {
> > > -               *val = 0xffffffff;
> >
> > I don't see the behavior you describe in PCI_OP_READ(), so dropping
> > this will lead to returning an uninitialized value?
> >
>
> Hello Geert,
>
> Thank you for looking into the patch.
>
> The described behaviour for PCI_OP_READ is part of the 01/24 [1] patch of
> the series.
>
> [1]:
> https://lore.kernel.org/linux-pci/b913b4966938b7cad8c049dc34093e6c4b2fae68.1634306198.git.naveennaidu479@xxxxxxxxx/T/#u

OK, in that case:
Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>

> It looks like, I did not add proper receipients for that patch and hence
> is leading to confusion. I really apologize for that.

Indeed. If there are dependencies, all recipients should receive all
dependencies.

> I do not know what the right approach here should be, should I resend
> the entire patch series, adding proper receipients OR should I reply to
> each of the patches for the drivers and add the link to the patch. I did
> not want to spam people with a lot of mails so I was confused as to what
> the right option is.

Probably a resend would be best.
Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds