[PATCH v6 4/4] PCI: qcom: Add RX margining settings for 16.0 GT/s

[Manivannan Sadhasivam via B4 Relay <devnull+manivannan.sadhasivam.linaro.org@kernel.org>]

From: Shashank Babu Chinta Venkata <quic_schintav@quicinc.com>

Add RX lane margining settings for 16.0 GT/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>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
[mani: dropped the code refactoring and minor changes]
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
 drivers/pci/controller/dwc/pcie-designware.h  | 18 ++++++++++++++++
 drivers/pci/controller/dwc/pcie-qcom-common.c | 31 +++++++++++++++++++++++++++
 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, 56 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 51744ad25575..f5be99731f7e 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -209,6 +209,24 @@
 
 #define PCIE_PL_CHK_REG_ERR_ADDR			0xB28
 
+/*
+ * 16.0 GT/s (GEN4) lane margining register definitions
+ */
+#define GEN4_LANE_MARGINING_1_OFF		0xb80
+#define MARGINING_MAX_VOLTAGE_OFFSET		GENMASK(29, 24)
+#define MARGINING_NUM_VOLTAGE_STEPS		GENMASK(22, 16)
+#define MARGINING_MAX_TIMING_OFFSET		GENMASK(13, 8)
+#define MARGINING_NUM_TIMING_STEPS		GENMASK(5, 0)
+
+#define GEN4_LANE_MARGINING_2_OFF		0xb84
+#define MARGINING_IND_ERROR_SAMPLER		BIT(28)
+#define MARGINING_SAMPLE_REPORTING_METHOD	BIT(27)
+#define MARGINING_IND_LEFT_RIGHT_TIMING		BIT(26)
+#define MARGINING_IND_UP_DOWN_VOLTAGE		BIT(25)
+#define MARGINING_VOLTAGE_SUPPORTED		BIT(24)
+#define MARGINING_MAXLANES			GENMASK(20, 16)
+#define MARGINING_SAMPLE_RATE_TIMING		GENMASK(13, 8)
+#define MARGINING_SAMPLE_RATE_VOLTAGE		GENMASK(5, 0)
 /*
  * 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 dc7d93db9dc5..99b75e7f085d 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-common.c
+++ b/drivers/pci/controller/dwc/pcie-qcom-common.c
@@ -43,3 +43,34 @@ void qcom_pcie_common_set_16gt_eq_settings(struct dw_pcie *pci)
 	dw_pcie_writel_dbi(pci, GEN3_EQ_CONTROL_OFF, reg);
 }
 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 |
+		MARGINING_NUM_VOLTAGE_STEPS |
+		MARGINING_MAX_TIMING_OFFSET |
+		MARGINING_NUM_TIMING_STEPS);
+	reg |= FIELD_PREP(MARGINING_MAX_VOLTAGE_OFFSET, 0x24) |
+		FIELD_PREP(MARGINING_NUM_VOLTAGE_STEPS, 0x78) |
+		FIELD_PREP(MARGINING_MAX_TIMING_OFFSET, 0x32) |
+		FIELD_PREP(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 |
+		MARGINING_SAMPLE_REPORTING_METHOD |
+		MARGINING_IND_LEFT_RIGHT_TIMING |
+		MARGINING_VOLTAGE_SUPPORTED;
+	reg &= ~(MARGINING_IND_UP_DOWN_VOLTAGE |
+		MARGINING_MAXLANES |
+		MARGINING_SAMPLE_RATE_TIMING |
+		MARGINING_SAMPLE_RATE_VOLTAGE);
+	reg |= FIELD_PREP(MARGINING_MAXLANES, pci->num_lanes) |
+		FIELD_PREP(MARGINING_SAMPLE_RATE_TIMING, 0x3f) |
+		FIELD_PREP(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);
diff --git a/drivers/pci/controller/dwc/pcie-qcom-common.h b/drivers/pci/controller/dwc/pcie-qcom-common.h
index 259e04b7bdf9..e9ddc901082e 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-common.h
+++ b/drivers/pci/controller/dwc/pcie-qcom-common.h
@@ -6,3 +6,4 @@
 #include "pcie-designware.h"
 
 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 af83470216e8..5c220f2ecafe 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-ep.c
+++ b/drivers/pci/controller/dwc/pcie-qcom-ep.c
@@ -487,8 +487,10 @@ static int qcom_pcie_perst_deassert(struct dw_pcie *pci)
 		goto err_disable_resources;
 	}
 
-	if (pcie_link_speed[pci->max_link_speed] == PCIE_SPEED_16_0GT)
+	if (pcie_link_speed[pci->max_link_speed] == 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 2742e82fdcb3..b0b1d8d34279 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -284,8 +284,10 @@ static int qcom_pcie_start_link(struct dw_pcie *pci)
 {
 	struct qcom_pcie *pcie = to_qcom_pcie(pci);
 
-	if (pcie_link_speed[pci->max_link_speed] == PCIE_SPEED_16_0GT)
+	if (pcie_link_speed[pci->max_link_speed] == 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)

-- 
2.25.1