linux-kernel - [PATCH v5 3/3] PCI: qcom: Add retry logic for link to be stable in L1ss

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Date:   Wed,  3 Aug 2022 16:58:54 +0530
From:   Krishna chaitanya chundru <quic_krichai@...cinc.com>
To:     helgaas@...nel.org
Cc:     linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, mka@...omium.org,
        quic_vbadigan@...cinc.com, quic_hemantk@...cinc.com,
        quic_nitegupt@...cinc.com, quic_skananth@...cinc.com,
        quic_ramkri@...cinc.com, manivannan.sadhasivam@...aro.org,
        swboyd@...omium.org, dmitry.baryshkov@...aro.org,
        Krishna chaitanya chundru <quic_krichai@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stanimir Varbanov <svarbanov@...sol.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: [PATCH v5 3/3] PCI: qcom: Add retry logic for link to be stable in L1ss

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@...cinc.com>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index f7dd5dc..f3201bd 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -1829,15 +1829,30 @@ static int __maybe_unused qcom_pcie_pm_suspend(struct device *dev)
 {
 	struct qcom_pcie *pcie = dev_get_drvdata(dev);
 	u32 val;
+	ktime_t timeout, start;
 
 	if (!pcie->cfg->supports_system_suspend)
 		return 0;
 
-	/* 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;
+	start = ktime_get();
+	/* Wait max 100 ms */
+	timeout = ktime_add_ms(start, 100);
+	while (1) {
+		bool timedout = ktime_after(ktime_get(), timeout);
+
+		/* 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_info(dev, "Link enters L1ss after %d ms\n",
+					ktime_to_ms(ktime_get() - start));
+			break;
+		}
+
+		if (timedout) {
+			dev_warn(dev, "Link is not in L1ss\n");
+			return 0;
+		}
+		usleep_range(1000, 1200);
 	}
 
 	if (pcie->cfg->ops->suspend)
-- 
2.7.4