Re: [PATCH v2 14/24] PCI: rcar: Remove redundant error fabrication when device read fails
flat view
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: 2021-10-18 11:32:47
Also in:
linux-pci, linux-renesas-soc, lkml
Hi Naveen, On Sat, Oct 16, 2021 at 5:33 PM Naveen Naidu [off-list ref] 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 <redacted>
Thanks for your patch!
quoted hunk ↗ jump to hunk
--- 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?
quoted hunk ↗ jump to hunk
+ 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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