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PCI: qcom: Add equalization settings for 8.0 GT/s and 32.0 GT/s

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Add lane equalization setting for 8.0 GT/s and 32.0 GT/s to enhance link
stability and avoid AER Correctable Errors reported on some platforms
(eg. SA8775P).

8.0 GT/s, 16.0 GT/s and 32.0 GT/s require the same equalization setting.
This setting is programmed into a group of shadow registers, which can be
switched to configure equalization for different speeds by writing 00b,
01b and 10b to `RATE_SHADOW_SEL`.

Hence, program equalization registers in a loop using link speed as index,
so that equalization setting can be programmed for 8.0 GT/s, 16.0 GT/s
and 32.0 GT/s.

Fixes: 489f14be0e ("arm64: dts: qcom: sa8775p: Add pcie0 and pcie1 nodes")
Co-developed-by: Qiang Yu <qiang.yu@oss.qualcomm.com>
Signed-off-by: Qiang Yu <qiang.yu@oss.qualcomm.com>
Signed-off-by: Ziyue Zhang <ziyue.zhang@oss.qualcomm.com>
[mani: wrapped the warning to fit 100 columns, used post-increment for loop]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://patch.msgid.link/20250904065225.1762793-2-ziyue.zhang@oss.qualcomm.com
This commit is contained in:
Ziyue Zhang 2025-09-04 14:52:23 +08:00 committed by Manivannan Sadhasivam
parent 45df22935b
commit 37bf0f4e39
5 changed files with 41 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
drivers/pci/controller/dwc/pcie-designware.h
View File

@ -123,7 +123,6 @@
#define GEN3_RELATED_OFF_GEN3_EQ_DISABLE BIT(16)
#define GEN3_RELATED_OFF_RATE_SHADOW_SEL_SHIFT 24
#define GEN3_RELATED_OFF_RATE_SHADOW_SEL_MASK GENMASK(25, 24)
#define GEN3_RELATED_OFF_RATE_SHADOW_SEL_16_0GT 0x1
#define GEN3_EQ_CONTROL_OFF 0x8A8
#define GEN3_EQ_CONTROL_OFF_FB_MODE GENMASK(3, 0)

58
drivers/pci/controller/dwc/pcie-qcom-common.c
View File

@ -8,9 +8,11 @@
#include "pcie-designware.h"
#include "pcie-qcom-common.h"
void qcom_pcie_common_set_16gt_equalization(struct dw_pcie *pci)
void qcom_pcie_common_set_equalization(struct dw_pcie *pci)
{
struct device *dev = pci->dev;
u32 reg;
u16 speed;
/*
* GEN3_RELATED_OFF register is repurposed to apply equalization
@ -19,32 +21,40 @@ void qcom_pcie_common_set_16gt_equalization(struct dw_pcie *pci)
* determines the data rate for which these 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,
GEN3_RELATED_OFF_RATE_SHADOW_SEL_16_0GT);
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);
for (speed = PCIE_SPEED_8_0GT; speed <= pcie_link_speed[pci->max_link_speed]; speed++) {
if (speed > PCIE_SPEED_32_0GT) {
dev_warn(dev, "Skipped equalization settings for unsupported data rate\n");
break;
}
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);
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,
speed - PCIE_SPEED_8_0GT);
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_equalization);
EXPORT_SYMBOL_GPL(qcom_pcie_common_set_equalization);
void qcom_pcie_common_set_16gt_lane_margining(struct dw_pcie *pci)
{

2
drivers/pci/controller/dwc/pcie-qcom-common.h
View File

@ -8,7 +8,7 @@
struct dw_pcie;
void qcom_pcie_common_set_16gt_equalization(struct dw_pcie *pci);
void qcom_pcie_common_set_equalization(struct dw_pcie *pci);
void qcom_pcie_common_set_16gt_lane_margining(struct dw_pcie *pci);
#endif

6
drivers/pci/controller/dwc/pcie-qcom-ep.c
View File

@ -511,10 +511,10 @@ 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) {
qcom_pcie_common_set_16gt_equalization(pci);
qcom_pcie_common_set_equalization(pci);
if (pcie_link_speed[pci->max_link_speed] == PCIE_SPEED_16_0GT)
qcom_pcie_common_set_16gt_lane_margining(pci);
}
/*
* The physical address of the MMIO region which is exposed as the BAR

6
drivers/pci/controller/dwc/pcie-qcom.c
View File

@ -322,10 +322,10 @@ 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) {
qcom_pcie_common_set_16gt_equalization(pci);
qcom_pcie_common_set_equalization(pci);
if (pcie_link_speed[pci->max_link_speed] == PCIE_SPEED_16_0GT)
qcom_pcie_common_set_16gt_lane_margining(pci);
}
/* Enable Link Training state machine */
if (pcie->cfg->ops->ltssm_enable)