[PATCH v6 2/5] PCI: qcom: Add retry logic for link to be stable in L1ss

[Krishna chaitanya chundru <quic_krichai@quicinc.com>]

Some specific devices are taking time to settle the link in L1ss.
So added a retry logic before returning from the suspend op.

Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 36 +++++++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 11 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index 6e04d0d..15c2067 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -1809,26 +1809,40 @@ static int qcom_pcie_probe(struct platform_device *pdev)
 static int __maybe_unused qcom_pcie_pm_suspend(struct qcom_pcie *pcie)
 {
 	u32 val;
+	ktime_t timeout, start;
 	struct dw_pcie *pci = pcie->pci;
 	struct device *dev = pci->dev;
 
 	if (!pcie->cfg->supports_system_suspend)
 		return 0;
 
-	/* if the link is not active turn off clocks */
-	if (!dw_pcie_link_up(pci)) {
-		dev_info(dev, "Link is not active\n");
-		goto suspend;
-	}
+	start = ktime_get();
+	/* Wait max 200 ms */
+	timeout = ktime_add_ms(start, 200);
 
-	/* if the link is not in l1ss don't turn off clocks */
-	val = readl(pcie->parf + PCIE20_PARF_PM_STTS);
-	if (!(val & PCIE20_PARF_PM_STTS_LINKST_IN_L1SUB)) {
-		dev_warn(dev, "Link is not in L1ss\n");
-		return 0;
+	while (1) {
+
+		if (!dw_pcie_link_up(pci)) {
+			dev_warn(dev, "Link is not active\n");
+			break;
+		}
+
+		/* if the link is not in l1ss don't turn off clocks */
+		val = readl(pcie->parf + PCIE20_PARF_PM_STTS);
+		if ((val & PCIE20_PARF_PM_STTS_LINKST_IN_L1SUB)) {
+			dev_dbg(dev, "Link enters L1ss after %d  ms\n",
+					ktime_to_ms(ktime_get() - start));
+			break;
+		}
+
+		if (ktime_after(ktime_get(), timeout)) {
+			dev_warn(dev, "Link is not in L1ss\n");
+			return 0;
+		}
+
+		udelay(1000);
 	}
 
-suspend:
 	if (pcie->cfg->ops->suspend)
 		pcie->cfg->ops->suspend(pcie);
 
-- 
2.7.4