| Message ID | 2544a93bf8725eecbea510e7ddbff6b5a5593c84.1634306198.git.naveennaidu479@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Geert Uytterhoeven |
| Headers | show |
| Series | Unify PCI error response checking | expand |
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
On 18/10, Geert Uytterhoeven wrote: > 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? > 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 It looks like, I did not add proper receipients for that patch and hence is leading to confusion. I really apologize for that. 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. Thanks, Naveen > > + 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
Hi Naveen, On Mon, Oct 18, 2021 at 1:52 PM Naveen Naidu <naveennaidu479@gmail.com> wrote: > On 18/10, Geert Uytterhoeven wrote: > > 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? > > > > 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 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
diff --git a/drivers/pci/controller/pcie-rcar-host.c b/drivers/pci/controller/pcie-rcar-host.c index 8f3131844e77..1324cb984ed5 100644 --- 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; + if (ret != PCIBIOS_SUCCESSFUL) return ret; - } if (size == 1) *val = (*val >> (BITS_PER_BYTE * (where & 3))) & 0xff;
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> --- drivers/pci/controller/pcie-rcar-host.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)