Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Mon, 18 Oct 2021 13:32:31 +0200 | Subject | Re: [PATCH v2 14/24] PCI: rcar: Remove redundant error fabrication when device read fails |
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Hi Naveen,
On Sat, Oct 16, 2021 at 5:33 PM Naveen Naidu <naveennaidu479@gmail.com> 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@gmail.com>
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?
> + if (ret != PCIBIOS_SUCCESSFUL) > return ret; > - } > > if (size == 1) > *val = (*val >> (BITS_PER_BYTE * (where & 3))) & 0xff;
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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