[PATCH v4 3/3] PCI: qcom: Add RX margining settings for 16 GT/s
From: Shashank Babu Chinta Venkata
Date: Wed May 01 2024 - 12:37:43 EST
Add RX lane margining settings for 16 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@xxxxxxxxxxx>
---
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 ed0045043847..343450c04e05 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
+/*
+ * 16 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 16c277b2e9d4..fe6f7dde5d8c 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-common.c
+++ b/drivers/pci/controller/dwc/pcie-qcom-common.c
@@ -53,6 +53,37 @@ 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 |
+ 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);
+
struct icc_path *qcom_pcie_common_icc_get_resource(struct dw_pcie *pci, const char *path)
{
struct icc_path *icc_mem_p;
diff --git a/drivers/pci/controller/dwc/pcie-qcom-common.h b/drivers/pci/controller/dwc/pcie-qcom-common.h
index 5c01f6c18b3b..c7eb87aa0677 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-common.h
+++ b/drivers/pci/controller/dwc/pcie-qcom-common.h
@@ -11,3 +11,4 @@ struct icc_path *qcom_pcie_common_icc_get_resource(struct dw_pcie *pci, const ch
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 7940222d35f6..2aea78da9c5b 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 525942f2cf98..9b3d7729b34b 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