PCI: dwc: Skip waiting for L2/L3 Ready if dw_pcie_rp::skip_l23_wait is true

[ Upstream commit 58a17b2 ]

In NXP i.MX6QP and i.MX7D SoCs, LTSSM registers are not accessible once
PME_Turn_Off message is broadcasted to the link. So there is no way to
verify whether the link has entered L2/L3 Ready state or not.

Hence, add a new flag 'dw_pcie_rp::skip_l23_ready' and set it to 'true' for
the above mentioned SoCs. This flag when set, will allow the DWC core to
skip polling for L2/L3 Ready state and just wait for 10ms as recommended in
the PCIe spec r6.0, sec 5.3.3.2.1.

Fixes: a528d1a ("PCI: imx6: Use DWC common suspend resume method")
Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
[mani: renamed flag to skip_l23_ready and reworded description]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260114083300.3689672-2-hongxing.zhu@nxp.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: Richard Zhu

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

@@ -116,6 +116,7 @@ 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_PCIE_FLAG_SKIP_L23_READY		BIT(12)
 
 #define imx_check_flag(pci, val)	(pci->drvdata->flags & val)
 
@@ -1795,6 +1796,8 @@ static int imx_pcie_probe(struct platform_device *pdev)
 		 */
 		imx_pcie_add_lut_by_rid(imx_pcie, 0);
 	} else {
+		if (imx_check_flag(imx_pcie, IMX_PCIE_FLAG_SKIP_L23_READY))
+			pci->pp.skip_l23_ready = true;
 		pci->pp.use_atu_msg = true;
 		ret = dw_pcie_host_init(&pci->pp);
 		if (ret < 0)
@@ -1856,6 +1859,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
 		.variant = IMX6QP,
 		.flags = IMX_PCIE_FLAG_IMX_PHY |
 			 IMX_PCIE_FLAG_SPEED_CHANGE_WORKAROUND |
+			 IMX_PCIE_FLAG_SKIP_L23_READY |
 			 IMX_PCIE_FLAG_SUPPORTS_SUSPEND,
 		.dbi_length = 0x200,
 		.gpr = "fsl,imx6q-iomuxc-gpr",
@@ -1872,6 +1876,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
 		.variant = IMX7D,
 		.flags = IMX_PCIE_FLAG_SUPPORTS_SUSPEND |
 			 IMX_PCIE_FLAG_HAS_APP_RESET |
+			 IMX_PCIE_FLAG_SKIP_L23_READY |
 			 IMX_PCIE_FLAG_HAS_PHY_RESET,
 		.gpr = "fsl,imx7d-iomuxc-gpr",
 		.mode_off[0] = IOMUXC_GPR12,

drivers/pci/controller/dwc/pcie-designware-host.c

@@ -1161,6 +1161,16 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci)
 			return ret;
 	}
 
+	/*
+	 * Some SoCs do not support reading the LTSSM register after
+	 * PME_Turn_Off broadcast. For those SoCs, skip waiting for L2/L3 Ready
+	 * state and wait 10ms as recommended in PCIe spec r6.0, sec 5.3.3.2.1.
+	 */
+	if (pci->pp.skip_l23_ready) {
+		mdelay(PCIE_PME_TO_L2_TIMEOUT_US/1000);
+		goto stop_link;
+	}
+
 	ret = read_poll_timeout(dw_pcie_get_ltssm, val,
 				val == DW_PCIE_LTSSM_L2_IDLE ||
 				val <= DW_PCIE_LTSSM_DETECT_WAIT,

drivers/pci/controller/dwc/pcie-designware.h

@@ -430,6 +430,7 @@ struct dw_pcie_rp {
 	struct pci_config_window *cfg;
 	bool			ecam_enabled;
 	bool			native_ecam;
+	bool                    skip_l23_ready;
 };
 
 struct dw_pcie_ep_ops {