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SubjectRe: [PATCH 3/5] PCI: brcmstb: enable CRS
On Thu, Apr 30, 2020 at 02:55:20PM -0400, Jim Quinlan wrote:
> From: Jim Quinlan <jquinlan@broadcom.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?

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@broadcom.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
>

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