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

Hi Naveen,

On Mon, Oct 18, 2021 at 1:52 PM Naveen Naidu [off-list ref] wrote:

On 18/10, Geert Uytterhoeven wrote:

quoted

On Sat, Oct 16, 2021 at 5:33 PM Naveen Naidu [off-list ref] wrote:

quoted

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 <redacted>

Thanks for your patch!

quoted

--- 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@gmail.com/T/#u (local)

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

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@linux-m68k.org

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
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