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

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Message-ID: <CA+-6iNwnMjAYZzYedBqooeJAbot_5A=9C8iFNMc=vdpnzmzVrw@mail.gmail.com>
Date:   Thu, 30 Apr 2020 17:00:36 -0400
From:   Jim Quinlan <james.quinlan@...adcom.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:PCI NATIVE HOST BRIDGE AND ENDPOINT DRIVERS" 
        <linux-pci@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/5] PCI: brcmstb: enable CRS

On Thu, Apr 30, 2020 at 4:32 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> On Thu, Apr 30, 2020 at 02:55:20PM -0400, Jim Quinlan wrote:
> > From: Jim Quinlan <jquinlan@...adcom.com>
> >
> > 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@...adcom.com>
> > ---
> >  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
> >