[PATCH 6.1 012/215] PCI: layerscape: Add workaround for lost link capabilities during reset

Greg Kroah-Hartman
2024-03-04T21:42:45Z

From: Xiaowei Bao <xiaowei.bao@nxp.com>

[ Upstream commit 17cf8661ee0f065c08152e611a568dd1fb0285f1 ]

The endpoint controller loses the Maximum Link Width and Supported Link Speed
value from the Link Capabilities Register - initially configured by the Reset
Configuration Word (RCW) - during a link-down or hot reset event.

Address this issue in the endpoint event handler.

Link: https://lore.kernel.org/r/20230720135834.1977616-2-Frank.Li@nxp.com
Fixes: a805770d8a22 ("PCI: layerscape: Add EP mode support")
Signed-off-by: Xiaowei Bao <xiaowei.bao@nxp.com>
Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Acked-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../pci/controller/dwc/pci-layerscape-ep.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)

diff --git a/drivers/pci/controller/dwc/pci-layerscape-ep.c b/drivers/pci/controller/dwc/pci-layerscape-ep.c
index 5b27554e071a1..dd7d74fecc48e 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 +83,19 @@ 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);
+
+ /*
+ * The values of the Maximum Link Width and Supported Link
+ * Speed from the Link Capabilities Register will be lost
+ * during link down or hot reset. Restore initial value
+ * that configured by the Reset Configuration Word (RCW).
+ */
+ dw_pcie_dbi_ro_wr_en(pci);
+ dw_pcie_writel_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);
@@ -214,6 +229,7 @@ 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);
@@ -250,6 +266,9 @@ 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;
--
2.43.0