During high data transmission rates such as 16 GT/s , there is an
increased risk of signal loss due to poor channel quality and
interference. This can impact receiver's ability to capture signals
accurately. Hence, signal compensation is achieved through appropriate
lane equalization settings at both transmitter and receiver. This will
result in increased PCIe signal strength.
Signed-off-by: Shashank Babu Chinta Venkata <quic_schintav@xxxxxxxxxxx>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
---
drivers/pci/controller/dwc/pcie-designware.h | 12 ++++++
drivers/pci/controller/dwc/pcie-qcom-common.c | 37 +++++++++++++++++++
drivers/pci/controller/dwc/pcie-qcom-common.h | 1 +
drivers/pci/controller/dwc/pcie-qcom-ep.c | 3 ++
drivers/pci/controller/dwc/pcie-qcom.c | 3 ++
5 files changed, 56 insertions(+)
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 53c4c8f399c8..50265a2fbb9f 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -126,6 +126,18 @@
#define GEN3_RELATED_OFF_RATE_SHADOW_SEL_SHIFT 24
#define GEN3_RELATED_OFF_RATE_SHADOW_SEL_MASK GENMASK(25, 24)
+#define GEN3_EQ_CONTROL_OFF 0x8a8
+#define GEN3_EQ_CONTROL_OFF_FB_MODE GENMASK(3, 0)
+#define GEN3_EQ_CONTROL_OFF_PHASE23_EXIT_MODE BIT(4)
+#define GEN3_EQ_CONTROL_OFF_PSET_REQ_VEC GENMASK(23, 8)
+#define GEN3_EQ_CONTROL_OFF_FOM_INC_INITIAL_EVAL BIT(24)
+
+#define GEN3_EQ_FB_MODE_DIR_CHANGE_OFF 0x8ac
+#define GEN3_EQ_FMDC_T_MIN_PHASE23 GENMASK(4, 0)
+#define GEN3_EQ_FMDC_N_EVALS GENMASK(9, 5)
+#define GEN3_EQ_FMDC_MAX_PRE_CUSROR_DELTA GENMASK(13, 10)
+#define GEN3_EQ_FMDC_MAX_POST_CUSROR_DELTA GENMASK(17, 14)
+
#define PCIE_PORT_MULTI_LANE_CTRL 0x8C0
#define PORT_MLTI_UPCFG_SUPPORT BIT(7)
diff --git a/drivers/pci/controller/dwc/pcie-qcom-common.c b/drivers/pci/controller/dwc/pcie-qcom-common.c
index 1d8992147bba..e085075557cd 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-common.c
+++ b/drivers/pci/controller/dwc/pcie-qcom-common.c
@@ -15,6 +15,43 @@
#include "pcie-designware.h"
#include "pcie-qcom-common.h"
+void qcom_pcie_common_set_16gt_eq_settings(struct dw_pcie *pci)
+{
+ u32 reg;
+
+ /*
+ * GEN3_RELATED_OFF register is repurposed to apply equalization
+ * settings at various data transmission rates through registers
+ * namely GEN3_EQ_*. RATE_SHADOW_SEL bit field of GEN3_RELATED_OFF
+ * determines data rate for which this equalization settings are
+ * applied.
+ */
+ reg = dw_pcie_readl_dbi(pci, GEN3_RELATED_OFF);
+ reg &= ~GEN3_RELATED_OFF_GEN3_ZRXDC_NONCOMPL;
+ reg &= ~GEN3_RELATED_OFF_RATE_SHADOW_SEL_MASK;
+ reg |= FIELD_PREP(GEN3_RELATED_OFF_RATE_SHADOW_SEL_MASK, 0x1);
+ dw_pcie_writel_dbi(pci, GEN3_RELATED_OFF, reg);
+
+ reg = dw_pcie_readl_dbi(pci, GEN3_EQ_FB_MODE_DIR_CHANGE_OFF);
+ reg &= ~(GEN3_EQ_FMDC_T_MIN_PHASE23 |
+ GEN3_EQ_FMDC_N_EVALS |
+ GEN3_EQ_FMDC_MAX_PRE_CUSROR_DELTA |
+ GEN3_EQ_FMDC_MAX_POST_CUSROR_DELTA);
+ reg |= FIELD_PREP(GEN3_EQ_FMDC_T_MIN_PHASE23, 0x1) |
+ FIELD_PREP(GEN3_EQ_FMDC_N_EVALS, 0xd) |
+ FIELD_PREP(GEN3_EQ_FMDC_MAX_PRE_CUSROR_DELTA, 0x5) |
+ FIELD_PREP(GEN3_EQ_FMDC_MAX_POST_CUSROR_DELTA, 0x5);
+ dw_pcie_writel_dbi(pci, GEN3_EQ_FB_MODE_DIR_CHANGE_OFF, reg);
+
+ reg = dw_pcie_readl_dbi(pci, GEN3_EQ_CONTROL_OFF);
+ reg &= ~(GEN3_EQ_CONTROL_OFF_FB_MODE |
+ GEN3_EQ_CONTROL_OFF_PHASE23_EXIT_MODE |
+ GEN3_EQ_CONTROL_OFF_FOM_INC_INITIAL_EVAL |
+ GEN3_EQ_CONTROL_OFF_PSET_REQ_VEC);
+ dw_pcie_writel_dbi(pci, GEN3_EQ_CONTROL_OFF, reg);
+}
+EXPORT_SYMBOL_GPL(qcom_pcie_common_set_16gt_eq_settings);
+
struct icc_path *qcom_pcie_common_icc_get_resource(struct dw_pcie *pci, const char *path)
{
struct icc_path *icc_p;
diff --git a/drivers/pci/controller/dwc/pcie-qcom-common.h b/drivers/pci/controller/dwc/pcie-qcom-common.h
index 897fa18e618a..c281582de12c 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-common.h
+++ b/drivers/pci/controller/dwc/pcie-qcom-common.h
@@ -13,3 +13,4 @@
struct icc_path *qcom_pcie_common_icc_get_resource(struct dw_pcie *pci, const char *path);
int qcom_pcie_common_icc_init(struct dw_pcie *pci, struct icc_path *icc_mem, u32 bandwidth);
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);
diff --git a/drivers/pci/controller/dwc/pcie-qcom-ep.c b/drivers/pci/controller/dwc/pcie-qcom-ep.c
index e1860026e134..823e33a4d745 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-ep.c
+++ b/drivers/pci/controller/dwc/pcie-qcom-ep.c
@@ -455,6 +455,9 @@ 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)
+ qcom_pcie_common_set_16gt_eq_settings(pci);
+
/*
* The physical address of the MMIO region which is exposed as the BAR
* should be written to MHI BASE registers.
diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index ee32590f1506..829b34391af1 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -280,6 +280,9 @@ 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)
+ qcom_pcie_common_set_16gt_eq_settings(pci);
+
/* Enable Link Training state machine */
if (pcie->cfg->ops->ltssm_enable)
pcie->cfg->ops->ltssm_enable(pcie);
--
2.46.0
