PCI: imx6: Add workaround for errata ERR051624

ERR051624: The Controller Without Vaux Cannot Exit L23 Ready Through Beacon
or PERST# De-assertion

When the auxiliary power is not available, the controller cannot exit from
L23 Ready with beacon or PERST# de-assertion when main power is not
removed. So the workaround is to set SS_RW_REG_1[SYS_AUX_PWR_DET] to 1.

This workaround is required irrespective of whether Vaux is supplied to the
link partner or not.

Signed-off-by: Richard Zhu <[email protected]>
[mani: subject and description rewording]
Signed-off-by: Manivannan Sadhasivam <[email protected]>
Reviewed-by: Frank Li <[email protected]>
Reviewed-by: Manivannan Sadhasivam <[email protected]>
Link: https://patch.msgid.link/[email protected]

Author: Richard Zhu

drivers/pci/controller/dwc/pci-imx6.c

@@ -48,6 +48,8 @@
 #define IMX95_PCIE_SS_RW_REG_0			0xf0
 #define IMX95_PCIE_REF_CLKEN			BIT(23)
 #define IMX95_PCIE_PHY_CR_PARA_SEL		BIT(9)
+#define IMX95_PCIE_SS_RW_REG_1			0xf4
+#define IMX95_PCIE_SYS_AUX_PWR_DET		BIT(31)
 
 #define IMX95_PE0_GEN_CTRL_1			0x1050
 #define IMX95_PCIE_DEVICE_TYPE			GENMASK(3, 0)
@@ -227,6 +229,19 @@ static unsigned int imx_pcie_grp_offset(const struct imx_pcie *imx_pcie)
 
 static int imx95_pcie_init_phy(struct imx_pcie *imx_pcie)
 {
+	/*
+	 * ERR051624: The Controller Without Vaux Cannot Exit L23 Ready
+	 * Through Beacon or PERST# De-assertion
+	 *
+	 * When the auxiliary power is not available, the controller
+	 * cannot exit from L23 Ready with beacon or PERST# de-assertion
+	 * when main power is not removed.
+	 *
+	 * Workaround: Set SS_RW_REG_1[SYS_AUX_PWR_DET] to 1.
+	 */
+	regmap_set_bits(imx_pcie->iomuxc_gpr, IMX95_PCIE_SS_RW_REG_1,
+			IMX95_PCIE_SYS_AUX_PWR_DET);
+
 	regmap_update_bits(imx_pcie->iomuxc_gpr,
 			IMX95_PCIE_SS_RW_REG_0,
 			IMX95_PCIE_PHY_CR_PARA_SEL,