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SubjectRe: [RFC PATCH 1/3] PCI: iproc: generate proper configuration access cycles
On Mon, 26 Oct 2015 10:18:14 -0700
Ray Jui <rjui@broadcom.com> wrote:

> Hi Jisheng,
>
> On 10/26/2015 4:02 AM, Jisheng Zhang wrote:
> > Inspired by Russell King's patch[1], I found current iproc also has the
> > same issue of "reading 32-bits from the command register, modifying the
> > command register, and then writing it back has the effect of clearing
> > any status bits that were indicating at that time" as pointed out by
> > Russell. This patch fix this issue by using the pci_generic_config_write.
> >
> > [1]http://www.spinics.net/lists/linux-pci/msg44869.html
> >
> > Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
> > ---
> > drivers/pci/host/pcie-iproc.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/host/pcie-iproc.c b/drivers/pci/host/pcie-iproc.c
> > index fe2efb1..0c423f2 100644
> > --- a/drivers/pci/host/pcie-iproc.c
> > +++ b/drivers/pci/host/pcie-iproc.c
> > @@ -111,7 +111,7 @@ static void __iomem *iproc_pcie_map_cfg_bus(struct pci_bus *bus,
> > static struct pci_ops iproc_pcie_ops = {
> > .map_bus = iproc_pcie_map_cfg_bus,
> > .read = pci_generic_config_read32,
> > - .write = pci_generic_config_write32,
> > + .write = pci_generic_config_write,
> > };
> >
> > static void iproc_pcie_reset(struct iproc_pcie *pcie)
> >
>
> I have already confirmed with the ASIC team that the current iProc PCIe
> controller requires 32-bit aligned access into the configuration space
> due to the way how it was integrated into various iProc SoCs including
> NSP, Cygnus, and NS2.
>
> This change will prevent the driver from working properly.
>
> I've informed our ASIC team about this issue and all future iProc based
> SoCs should be able to support 8-bit, 16-bit access and therefore
> pci_generic_config_write/read can be used for those SoCs.
>
> Thanks,
>
> Ray

Got it.

Thanks for the information,
Jisheng


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