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From: Shashank Babu Chinta Venkata <quic_schintav@quicinc.com>
To: <agross@kernel.org>, <andersson@kernel.org>, <konrad.dybcio@linaro.org>,
        <mani@kernel.org>
CC: <quic_msarkar@quicinc.com>, <quic_kraravin@quicinc.com>,
        Lorenzo Pieralisi
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        =?UTF-8?q?Krzysztof=20Wilczy=C5=84ski?=
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        Rob Herring <robh@kernel.org>, Bjorn Helgaas
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        Jingoo Han <jingoohan1@gmail.com>,
        Gustavo Pimentel
	<gustavo.pimentel@synopsys.com>,
        Manivannan Sadhasivam
	<manivannan.sadhasivam@linaro.org>,
        Serge Semin <fancer.lancer@gmail.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
        Conor Dooley
	<conor.dooley@microchip.com>,
        <linux-kernel@vger.kernel.org>, <linux-pci@vger.kernel.org>,
        <linux-arm-msm@vger.kernel.org>
Subject: [PATCH v3 3/3] PCI: qcom: Add rx margining settings for 16GT/s
Date: Thu, 18 Apr 2024 17:09:36 -0700
Message-ID: <20240419001013.28788-4-quic_schintav@quicinc.com>
In-Reply-To: <20240419001013.28788-1-quic_schintav@quicinc.com>
References: <20240419001013.28788-1-quic_schintav@quicinc.com>
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Add rx lane margining settings for 16GT/s(GEN 4) data rate. These
settings improve link stability while operating at high date rates
and helps to improve signal quality.

Signed-off-by: Shashank Babu Chinta Venkata <quic_schintav@quicinc.com>
---
 drivers/pci/controller/dwc/pcie-designware.h  | 18 ++++++++++++++
 drivers/pci/controller/dwc/pcie-qcom-common.c | 24 +++++++++++++++++++
 drivers/pci/controller/dwc/pcie-qcom-common.h |  1 +
 drivers/pci/controller/dwc/pcie-qcom-ep.c     |  4 +++-
 drivers/pci/controller/dwc/pcie-qcom.c        |  4 +++-
 5 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index ad771bb52d29..e8c48855143f 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -203,6 +203,24 @@
 
 #define PCIE_PL_CHK_REG_ERR_ADDR			0xB28
 
+/*
+ * GEN4 lane margining register definitions
+ */
+#define GEN4_LANE_MARGINING_1_OFF		0xb80
+#define MARGINING_MAX_VOLTAGE_OFFSET(n)		FIELD_PREP(GENMASK(29, 24), n)
+#define MARGINING_NUM_VOLTAGE_STEPS(n)		FIELD_PREP(GENMASK(22, 16), n)
+#define MARGINING_MAX_TIMING_OFFSET(n)		FIELD_PREP(GENMASK(13, 8), n)
+#define MARGINING_NUM_TIMING_STEPS(n)		FIELD_PREP(GENMASK(5, 0), n)
+
+#define GEN4_LANE_MARGINING_2_OFF		0xb84
+#define MARGINING_IND_ERROR_SAMPLER(n)		FIELD_PREP(BIT(28), n)
+#define MARGINING_SAMPLE_REPORTING_METHOD(n)	FIELD_PREP(BIT(27), n)
+#define MARGINING_IND_LEFT_RIGHT_TIMING(n)	FIELD_PREP(BIT(26), n)
+#define MARGINING_IND_UP_DOWN_VOLTAGE(n)	FIELD_PREP(BIT(25), n)
+#define MARGINING_VOLTAGE_SUPPORTED(n)		FIELD_PREP(BIT(24), n)
+#define MARGINING_MAXLANES(n)			FIELD_PREP(GENMASK(20, 16), n)
+#define MARGINING_SAMPLE_RATE_TIMING(n)		FIELD_PREP(GENMASK(13, 8), n)
+#define MARGINING_SAMPLE_RATE_VOLTAGE(n)	FIELD_PREP(GENMASK(5, 0), n)
 /*
  * iATU Unroll-specific register definitions
  * From 4.80 core version the address translation will be made by unroll
diff --git a/drivers/pci/controller/dwc/pcie-qcom-common.c b/drivers/pci/controller/dwc/pcie-qcom-common.c
index a6f3eb4c3ee6..3279314ae78c 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-common.c
+++ b/drivers/pci/controller/dwc/pcie-qcom-common.c
@@ -46,6 +46,30 @@ void qcom_pcie_common_set_16gt_eq_settings(struct dw_pcie *pci)
 }
 EXPORT_SYMBOL_GPL(qcom_pcie_common_set_16gt_eq_settings);
 
+void qcom_pcie_common_set_16gt_rx_margining_settings(struct dw_pcie *pci)
+{
+	u32 reg;
+
+	reg = dw_pcie_readl_dbi(pci, GEN4_LANE_MARGINING_1_OFF);
+	reg = MARGINING_MAX_VOLTAGE_OFFSET(0x24) |
+		MARGINING_NUM_VOLTAGE_STEPS(0x78) |
+		MARGINING_MAX_TIMING_OFFSET(0x32) |
+		MARGINING_NUM_TIMING_STEPS(0x10);
+	dw_pcie_writel_dbi(pci, GEN4_LANE_MARGINING_1_OFF, reg);
+
+	reg = dw_pcie_readl_dbi(pci, GEN4_LANE_MARGINING_2_OFF);
+	reg = MARGINING_IND_ERROR_SAMPLER(1) |
+		MARGINING_SAMPLE_REPORTING_METHOD(1) |
+		MARGINING_IND_LEFT_RIGHT_TIMING(1) |
+		MARGINING_VOLTAGE_SUPPORTED(1) |
+		MARGINING_IND_UP_DOWN_VOLTAGE(0) |
+		MARGINING_MAXLANES(pci->num_lanes) |
+		MARGINING_SAMPLE_RATE_TIMING(0x3f) |
+		MARGINING_SAMPLE_RATE_VOLTAGE(0x3f);
+	dw_pcie_writel_dbi(pci, GEN4_LANE_MARGINING_2_OFF, reg);
+}
+EXPORT_SYMBOL_GPL(qcom_pcie_common_set_16gt_rx_margining_settings);
+
 int qcom_pcie_common_icc_get_resource(struct dw_pcie *pci, struct icc_path **icc_mem_p)
 {
 	*icc_mem_p = devm_of_icc_get(pci->dev, "pcie-mem");
diff --git a/drivers/pci/controller/dwc/pcie-qcom-common.h b/drivers/pci/controller/dwc/pcie-qcom-common.h
index e72c651b0d28..b9eb78fcc766 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-common.h
+++ b/drivers/pci/controller/dwc/pcie-qcom-common.h
@@ -11,3 +11,4 @@ int qcom_pcie_common_icc_get_resource(struct dw_pcie *pci, struct icc_path **icc
 int qcom_pcie_common_icc_init(struct dw_pcie *pci, struct icc_path *icc_mem);
 void qcom_pcie_common_icc_update(struct dw_pcie *pci, struct icc_path *icc_mem);
 void qcom_pcie_common_set_16gt_eq_settings(struct dw_pcie *pci);
+void qcom_pcie_common_set_16gt_rx_margining_settings(struct dw_pcie *pci);
diff --git a/drivers/pci/controller/dwc/pcie-qcom-ep.c b/drivers/pci/controller/dwc/pcie-qcom-ep.c
index cb75a874f76c..3032dd91514c 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-ep.c
+++ b/drivers/pci/controller/dwc/pcie-qcom-ep.c
@@ -438,8 +438,10 @@ static int qcom_pcie_perst_deassert(struct dw_pcie *pci)
 		goto err_disable_resources;
 	}
 
-	if (pcie_link_speed[pci->link_gen] == PCIE_SPEED_16_0GT)
+	if (pcie_link_speed[pci->link_gen] == PCIE_SPEED_16_0GT) {
 		qcom_pcie_common_set_16gt_eq_settings(pci);
+		qcom_pcie_common_set_16gt_rx_margining_settings(pci);
+	}
 
 	/*
 	 * The physical address of the MMIO region which is exposed as the BAR
diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index acf66f974edc..f69364ecf2de 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -263,8 +263,10 @@ static int qcom_pcie_start_link(struct dw_pcie *pci)
 {
 	struct qcom_pcie *pcie = to_qcom_pcie(pci);
 
-	if (pcie_link_speed[pci->link_gen] == PCIE_SPEED_16_0GT)
+	if (pcie_link_speed[pci->link_gen] == PCIE_SPEED_16_0GT) {
 		qcom_pcie_common_set_16gt_eq_settings(pci);
+		qcom_pcie_common_set_16gt_rx_margining_settings(pci);
+	}
 
 	/* Enable Link Training state machine */
 	if (pcie->cfg->ops->ltssm_enable)
-- 
2.43.2