linux-kernel - [PATCH v2 3/3] phy: qcom-qmp-pcie: Add support for keeping refclk always on

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Message-ID: <20231107-refclk_always_on-v2-3-de23962fc4b3@quicinc.com>
Date:   Tue, 7 Nov 2023 17:56:15 +0530
From:   Krishna chaitanya chundru <quic_krichai@...cinc.com>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>
CC:     <linux-arm-msm@...r.kernel.org>, <linux-phy@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <quic_vbadigan@...cinc.com>, <quic_ramkri@...cinc.com>,
        <quic_nitegupt@...cinc.com>, <quic_skananth@...cinc.com>,
        <quic_vpernami@...cinc.com>, <quic_parass@...cinc.com>,
        "Krishna chaitanya chundru" <quic_krichai@...cinc.com>
Subject: [PATCH v2 3/3] phy: qcom-qmp-pcie: Add support for keeping refclk
 always on

In PCIe low power states like L1.1 or L1.2 the phy will stop
supplying refclk to endpoint. If endpoint asserts clkreq to bring
back link L0, then RC needs to provide refclk to endpoint.

If there is some issues in platform with clkreq signal propagation
to host and due to that host will not send refclk which results PCIe link
down. For those platforms phy needs to provide refclk even in low power
states.

Add a flag to keep refclk always supplied to endpoint.

Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
---
 drivers/phy/qualcomm/phy-qcom-qmp-pcie.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
index 74d03d217ff2..a8d6d69e3f74 100644
--- a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
+++ b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
@@ -43,6 +43,8 @@
 /* QPHY_PCS_STATUS bit */
 #define PHYSTATUS				BIT(6)
 #define PHYSTATUS_4_20				BIT(7)
+/* PCS_PCIE_ENDPOINT_REFCLK_CNTRL */
+#define EPCLK_ALWAYS_ON_EN			BIT(6)
 
 #define PHY_INIT_COMPLETE_TIMEOUT		10000
 
@@ -2264,6 +2266,8 @@ struct qmp_pcie {
 	struct phy *phy;
 	int mode;
 
+	bool refclk_always_on;
+
 	struct clk_fixed_rate pipe_clk_fixed;
 };
 
@@ -3179,6 +3183,10 @@ static void qmp_pcie_init_registers(struct qmp_pcie *qmp, const struct qmp_phy_c
 	qmp_pcie_configure(pcs, tbls->pcs, tbls->pcs_num);
 	qmp_pcie_configure(pcs_misc, tbls->pcs_misc, tbls->pcs_misc_num);
 
+	if (qmp->refclk_always_on && cfg->regs[QPHY_PCS_ENDPOINT_REFCLK_CNTRL])
+		qphy_setbits(pcs_misc, cfg->regs[QPHY_PCS_ENDPOINT_REFCLK_CNTRL],
+			     EPCLK_ALWAYS_ON_EN);
+
 	if (cfg->lanes >= 4 && qmp->tcsr_4ln_config) {
 		qmp_pcie_configure(serdes, cfg->serdes_4ln_tbl, cfg->serdes_4ln_num);
 		qmp_pcie_init_port_b(qmp, tbls);
@@ -3701,6 +3709,12 @@ static int qmp_pcie_probe(struct platform_device *pdev)
 	if (ret)
 		goto err_node_put;
 
+	qmp->refclk_always_on = of_property_read_bool(dev->of_node, "qcom,refclk-always-on");
+	if (qmp->refclk_always_on && !qmp->cfg->regs[QPHY_PCS_ENDPOINT_REFCLK_CNTRL]) {
+		dev_err(dev, "refclk is always on is present but refclk cntrl offset is not present\n");
+		goto err_node_put;
+	}
+
 	ret = phy_pipe_clk_register(qmp, np);
 	if (ret)
 		goto err_node_put;

-- 
2.42.0