[v4,5/7] PCI: imx6: Let i.MX95 PCIe compliance with 8GT/s Receiver Impedance ECN

Commit Message

Richard Zhu April 3, 2025, 5:39 a.m. UTC

ERR051586: Compliance with 8GT/s Receiver Impedance ECN.

The default value of GEN3_RELATED_OFF[GEN3_ZRXDC_NONCOMPL] is 1 which
makes receiver non-compliant with the ZRX-DC parameter for 2.5 GT/s when
operating at 8 GT/s or higher. It causes unnecessary timeout in L1.

Workaround: Program GEN3_RELATED_OFF[GEN3_ZRXDC_NONCOMPL] to 0.

Signed-off-by: Richard Zhu <[e-mail]>
Reviewed-by: Frank Li <[e-mail]>
Reviewed-by: Manivannan Sadhasivam <[e-mail]>
---
 drivers/pci/controller/dwc/pci-imx6.c | 31 +++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

Patch

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index abaf6b13a8d5..2232436709f5 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -110,6 +110,7 @@  enum imx_pcie_variants {
  */
 #define IMX_PCIE_FLAG_BROKEN_SUSPEND		BIT(9)
 #define IMX_PCIE_FLAG_HAS_LUT			BIT(10)
+#define IMX_PCIE_FLAG_8GT_ECN_ERR051586		BIT(11)
 
 #define imx_check_flag(pci, val)	(pci->drvdata->flags & val)
 
@@ -1256,6 +1257,32 @@  static void imx_pcie_host_exit(struct dw_pcie_rp *pp)
 		regulator_disable(imx_pcie->vpcie);
 }
 
+static void imx_pcie_host_post_init(struct dw_pcie_rp *pp)
+{
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+	struct imx_pcie *imx_pcie = to_imx_pcie(pci);
+	u32 val;
+
+	if (imx_pcie->drvdata->flags & IMX_PCIE_FLAG_8GT_ECN_ERR051586) {
+		/*
+		 * ERR051586: Compliance with 8GT/s Receiver Impedance ECN
+		 *
+		 * The default value of GEN3_RELATED_OFF[GEN3_ZRXDC_NONCOMPL]
+		 * is 1 which makes receiver non-compliant with the ZRX-DC
+		 * parameter for 2.5 GT/s when operating at 8 GT/s or higher.
+		 * It causes unnecessary timeout in L1.
+		 *
+		 * Workaround: Program GEN3_RELATED_OFF[GEN3_ZRXDC_NONCOMPL]
+		 * to 0.
+		 */
+		dw_pcie_dbi_ro_wr_en(pci);
+		val = dw_pcie_readl_dbi(pci, GEN3_RELATED_OFF);
+		val &= ~GEN3_RELATED_OFF_GEN3_ZRXDC_NONCOMPL;
+		dw_pcie_writel_dbi(pci, GEN3_RELATED_OFF, val);
+		dw_pcie_dbi_ro_wr_dis(pci);
+	}
+}
+
 static u64 imx_pcie_cpu_addr_fixup(struct dw_pcie *pcie, u64 cpu_addr)
 {
 	struct imx_pcie *imx_pcie = to_imx_pcie(pcie);
@@ -1297,6 +1324,7 @@  static const struct dw_pcie_host_ops imx_pcie_host_ops = {
 static const struct dw_pcie_host_ops imx_pcie_host_dw_pme_ops = {
 	.init = imx_pcie_host_init,
 	.deinit = imx_pcie_host_exit,
+	.post_init = imx_pcie_host_post_init,
 };
 
 static const struct dw_pcie_ops dw_pcie_ops = {
@@ -1396,6 +1424,7 @@  static int imx_add_pcie_ep(struct imx_pcie *imx_pcie,
 	struct device *dev = pci->dev;
 
 	imx_pcie_host_init(pp);
+	imx_pcie_host_post_init(pp);
 	ep = &pci->ep;
 	ep->ops = &pcie_ep_ops;
 
@@ -1805,6 +1834,7 @@  static const struct imx_pcie_drvdata drvdata[] = {
 		.variant = IMX95,
 		.flags = IMX_PCIE_FLAG_HAS_SERDES |
 			 IMX_PCIE_FLAG_HAS_LUT |
+			 IMX_PCIE_FLAG_8GT_ECN_ERR051586 |
 			 IMX_PCIE_FLAG_SUPPORTS_SUSPEND,
 		.ltssm_off = IMX95_PE0_GEN_CTRL_3,
 		.ltssm_mask = IMX95_PCIE_LTSSM_EN,
@@ -1858,6 +1888,7 @@  static const struct imx_pcie_drvdata drvdata[] = {
 	[IMX95_EP] = {
 		.variant = IMX95_EP,
 		.flags = IMX_PCIE_FLAG_HAS_SERDES |
+			 IMX_PCIE_FLAG_8GT_ECN_ERR051586 |
 			 IMX_PCIE_FLAG_SUPPORT_64BIT,
 		.ltssm_off = IMX95_PE0_GEN_CTRL_3,
 		.ltssm_mask = IMX95_PCIE_LTSSM_EN,