[PATCH 2/2] PCI: layerscape: Add the workaround for lost link capablities during reset

[Rob Herring]

On Thu, Jun 15, 2023 at 10:41 AM Frank Li <Frank.Li at nxp.com> wrote:
>
> From: Xiaowei Bao <xiaowei.bao at nxp.com>
>
> A workaround for the issue where the PCI Express Endpoint (EP) controller
> loses the values of the Maximum Link Width and Supported Link Speed from
> the Link Capabilities Register, which initially configured by the Reset
> Configuration Word (RCW) during a link-down or hot reset event.

What makes this Layerscape specific? Seems like something internal to DWC.

>
> Signed-off-by: Xiaowei Bao <xiaowei.bao at nxp.com>
> Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou at nxp.com>
> Signed-off-by: Frank Li <Frank.Li at nxp.com>
> ---
>  drivers/pci/controller/dwc/pci-layerscape-ep.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pci-layerscape-ep.c b/drivers/pci/controller/dwc/pci-layerscape-ep.c
> index 4e4fdd1dfea7..2ef02d827eeb 100644
> --- a/drivers/pci/controller/dwc/pci-layerscape-ep.c
> +++ b/drivers/pci/controller/dwc/pci-layerscape-ep.c
> @@ -45,6 +45,7 @@ struct ls_pcie_ep {
>         struct pci_epc_features         *ls_epc;
>         const struct ls_pcie_ep_drvdata *drvdata;
>         int                             irq;
> +       u32                             lnkcap;
>         bool                            big_endian;
>  };
>
> @@ -73,6 +74,7 @@ static irqreturn_t ls_pcie_ep_event_handler(int irq, void *dev_id)
>         struct ls_pcie_ep *pcie = dev_id;
>         struct dw_pcie *pci = pcie->pci;
>         u32 val, cfg;
> +       u8 offset;
>
>         val = ls_lut_readl(pcie, PEX_PF0_PME_MES_DR);
>         ls_lut_writel(pcie, PEX_PF0_PME_MES_DR, val);
> @@ -81,6 +83,13 @@ static irqreturn_t ls_pcie_ep_event_handler(int irq, void *dev_id)
>                 return IRQ_NONE;
>
>         if (val & PEX_PF0_PME_MES_DR_LUD) {
> +
> +               offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> +
> +               dw_pcie_dbi_ro_wr_en(pci);
> +               dw_pcie_writew_dbi(pci, offset + PCI_EXP_LNKCAP, pcie->lnkcap);
> +               dw_pcie_dbi_ro_wr_dis(pci);
> +
>                 cfg = ls_lut_readl(pcie, PEX_PF0_CONFIG);
>                 cfg |= PEX_PF0_CFG_READY;
>                 ls_lut_writel(pcie, PEX_PF0_CONFIG, cfg);
> @@ -216,6 +225,7 @@ static int __init ls_pcie_ep_probe(struct platform_device *pdev)
>         struct ls_pcie_ep *pcie;
>         struct pci_epc_features *ls_epc;
>         struct resource *dbi_base;
> +       u8 offset;
>         int ret;
>
>         pcie = devm_kzalloc(dev, sizeof(*pcie), GFP_KERNEL);
> @@ -252,6 +262,9 @@ static int __init ls_pcie_ep_probe(struct platform_device *pdev)
>
>         platform_set_drvdata(pdev, pcie);
>
> +       offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> +       pcie->lnkcap = dw_pcie_readl_dbi(pci, offset + PCI_EXP_LNKCAP);
> +
>         ret = dw_pcie_ep_init(&pci->ep);
>         if (ret)
>                 return ret;
> --
> 2.34.1
>