Re: [PATCH 3/5] PCI: brcmstb: enable CRS

From: Jim Quinlan
Date: Thu Apr 30 2020 - 17:00:52 EST


On Thu, Apr 30, 2020 at 4:32 PM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
>
> On Thu, Apr 30, 2020 at 02:55:20PM -0400, Jim Quinlan wrote:
> > From: Jim Quinlan <jquinlan@xxxxxxxxxxxx>
> >
> > Configuration Retry Request Status is off by default on this
> > PCIe controller. Turn it on.
>
> Are you talking about CRS itself, i.e., the ability of a Root Port to
> deal with Completions with Configuration Retry Request Status? That
> really shouldn't be switchable in the hardware since it's a required
> feature for all PCIe devices.
>
> Or are you talking about CRS Software Visibility, which is controlled
> by a bit in the PCIe Root Control register? That *should* be managed
> by the PCI core in pci_enable_crs(). Does that generic method of
> controlling it not work for this device?
>
My mistake; the commit will be dropped.

Thanks,
Jim
> It looks like maybe the latter, since the generic:
>
> #define PCI_EXP_RTCTL_CRSSVE 0x0010
>
> matches your new PCIE_RC_CFG_PCIE_ROOT_CAP_CONTROL_RC_CRS_EN_MASK.
>
> If pci_enable_crs() doesn't work on this device, it sounds like a
> hardware defect that we need to work around, but I'm not sure that
> just enabling it unconditionally here is the right thing.
>
> > Signed-off-by: Jim Quinlan <jquinlan@xxxxxxxxxxxx>
> > ---
> > drivers/pci/controller/pcie-brcmstb.c | 9 +++++++++
> > 1 file changed, 9 insertions(+)
> >
> > diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> > index 5b0dec5971b8..2bc913c0262c 100644
> > --- a/drivers/pci/controller/pcie-brcmstb.c
> > +++ b/drivers/pci/controller/pcie-brcmstb.c
> > @@ -34,6 +34,9 @@
> > #define BRCM_PCIE_CAP_REGS 0x00ac
> >
> > /* Broadcom STB PCIe Register Offsets */
> > +#define PCIE_RC_CFG_PCIE_ROOT_CAP_CONTROL 0x00c8
> > +#define PCIE_RC_CFG_PCIE_ROOT_CAP_CONTROL_RC_CRS_EN_MASK 0x10
> > +
> > #define PCIE_RC_CFG_VENDOR_VENDOR_SPECIFIC_REG1 0x0188
> > #define PCIE_RC_CFG_VENDOR_VENDOR_SPECIFIC_REG1_ENDIAN_MODE_BAR2_MASK 0xc
> > #define PCIE_RC_CFG_VENDOR_SPCIFIC_REG1_LITTLE_ENDIAN 0x0
> > @@ -827,6 +830,12 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
> > pci_speed_string(pcie_link_speed[cls]), nlw,
> > ssc_good ? "(SSC)" : "(!SSC)");
> >
> > + /* Enable configuration request retry (CRS) */
> > + tmp = readl(base + PCIE_RC_CFG_PCIE_ROOT_CAP_CONTROL);
> > + u32p_replace_bits(&tmp, 1,
> > + PCIE_RC_CFG_PCIE_ROOT_CAP_CONTROL_RC_CRS_EN_MASK);
> > + writel(tmp, base + PCIE_RC_CFG_PCIE_ROOT_CAP_CONTROL);
> > +
> > /* PCIe->SCB endian mode for BAR */
> > tmp = readl(base + PCIE_RC_CFG_VENDOR_VENDOR_SPECIFIC_REG1);
> > u32p_replace_bits(&tmp, PCIE_RC_CFG_VENDOR_SPCIFIC_REG1_LITTLE_ENDIAN,
> > --
> > 2.17.1
> >