[PATCH v2 0/2] Add Equalization Settings for 8.0 GT/s and Add PCIe Lane Equalization Preset Properties for 8.0 GT/s and 16.0 GT/s

[PATCH v2 0/2] Add Equalization Settings for 8.0 GT/s and Add PCIe Lane Equalization Preset Properties for 8.0 GT/s and 16.0 GT/s

[Ziyue Zhang]

This series adds add equalization settings for 8.0 GT/s, and add PCIe lane equalization
preset properties for 8.0 GT/s and 16.0 GT/s for sa8775p ride platform, which fix AER
errors.

While equalization settings for 16 GT/s have already been set, this update adds the
required equalization settings for PCIe operating at 8.0 GT/s, including the
configuration of shadow registers, ensuring optimal performance and stability.

The DT change for sa8775p add PCIe lane equalization preset properties for 8 GT/s
and 16 GT/s data rates used in lane equalization procedure.

Signed-off-by: Ziyue Zhang <quic_ziyuzhan@quicinc.com>

Changes in v2:
- Update code in pcie-qcom-common.c make it easier to read. (Neil)
- Fix the compile error.
- Link to v1: https://lore.kernel.org/all/20250604091946.1890602-1-quic_ziyuzhan@quicinc.com

Ziyue Zhang (2):
  PCI: qcom: Add equalization settings for 8.0 GT/s
  arm64: dts: qcom: sa8775p: Add PCIe lane equalization preset
    properties

 arch/arm64/boot/dts/qcom/sa8775p.dtsi         |  6 ++
 drivers/pci/controller/dwc/pcie-designware.h  |  1 -
 drivers/pci/controller/dwc/pcie-qcom-common.c | 60 +++++++++++--------
 drivers/pci/controller/dwc/pcie-qcom-common.h |  2 +-
 drivers/pci/controller/dwc/pcie-qcom-ep.c     |  6 +-
 drivers/pci/controller/dwc/pcie-qcom.c        |  6 +-
 6 files changed, 49 insertions(+), 32 deletions(-)


base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494
-- 
2.34.1


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[PATCH v2 1/2] PCI: qcom: Add equalization settings for 8.0 GT/s

[Ziyue Zhang]

Adding lane equalization setting for 8.0 GT/s to enhance link stability
and fix AER correctable errors reported on some platforms (eg. SA8775P).

8.0 GT/s and 16.0GT/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 GEN speeds by writing 00b, 01b
to `RATE_SHADOW_SEL`.

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

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 <quic_ziyuzhan@quicinc.com>
---
 drivers/pci/controller/dwc/pcie-designware.h  |  1 -
 drivers/pci/controller/dwc/pcie-qcom-common.c | 60 +++++++++++--------
 drivers/pci/controller/dwc/pcie-qcom-common.h |  2 +-
 drivers/pci/controller/dwc/pcie-qcom-ep.c     |  6 +-
 drivers/pci/controller/dwc/pcie-qcom.c        |  6 +-
 5 files changed, 43 insertions(+), 32 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index ce9e18554e42..388306991467 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -127,7 +127,6 @@
 #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)
diff --git a/drivers/pci/controller/dwc/pcie-qcom-common.c b/drivers/pci/controller/dwc/pcie-qcom-common.c
index 3aad19b56da8..4ff97ec13818 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-common.c
+++ b/drivers/pci/controller/dwc/pcie-qcom-common.c
@@ -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)
 {
 	u32 reg;
+	u16 speed, max_speed = PCIE_SPEED_16_0GT;
+	struct device *dev = pci->dev;
 
 	/*
 	 * GEN3_RELATED_OFF register is repurposed to apply equalization
@@ -18,33 +20,43 @@ void qcom_pcie_common_set_16gt_equalization(struct dw_pcie *pci)
 	 * GEN3_EQ_*. The RATE_SHADOW_SEL bit field of GEN3_RELATED_OFF
 	 * determines the data rate for which these equalization settings are
 	 * applied.
+	 *
+	 * TODO:
+	 * EQ settings need to be added for 32.0 T/s in future
 	 */
-	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);
+	if (pcie_link_speed[pci->max_link_speed] < PCIE_SPEED_32_0GT)
+		max_speed = pcie_link_speed[pci->max_link_speed];
+	else
+		dev_warn(dev, "The target supports 32.0 GT/s, but the EQ setting for 32.0 GT/s is not configured.\n");
 
-	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 <= max_speed; ++speed) {
+		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_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_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)
 {
diff --git a/drivers/pci/controller/dwc/pcie-qcom-common.h b/drivers/pci/controller/dwc/pcie-qcom-common.h
index 7d88d29e4766..7f5ca2fd9a72 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-common.h
+++ b/drivers/pci/controller/dwc/pcie-qcom-common.h
@@ -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
diff --git a/drivers/pci/controller/dwc/pcie-qcom-ep.c b/drivers/pci/controller/dwc/pcie-qcom-ep.c
index bf7c6ac0f3e3..aaf060bf39d4 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-ep.c
+++ b/drivers/pci/controller/dwc/pcie-qcom-ep.c
@@ -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
diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index c789e3f85655..0fcb17ffd2e9 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -298,10 +298,10 @@ 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)
-- 
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[PATCH v2 2/2] arm64: dts: qcom: sa8775p: Add PCIe lane equalization preset properties

[Ziyue Zhang]

Add PCIe lane equalization preset properties with all values set to 5 for
8.0 GT/s and 16.0 GT/s data rates to enhance link stability.

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 <quic_ziyuzhan@quicinc.com>
---
 arch/arm64/boot/dts/qcom/sa8775p.dtsi | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm64/boot/dts/qcom/sa8775p.dtsi b/arch/arm64/boot/dts/qcom/sa8775p.dtsi
index 45f536633f64..16caf1da0708 100644
--- a/arch/arm64/boot/dts/qcom/sa8775p.dtsi
+++ b/arch/arm64/boot/dts/qcom/sa8775p.dtsi
@@ -7159,6 +7159,9 @@ pcie0: pcie@1c00000 {
 		phys = <&pcie0_phy>;
 		phy-names = "pciephy";
 
+		eq-presets-8gts = /bits/ 16 <0x5555 0x5555>;
+		eq-presets-16gts = /bits/ 8 <0x55 0x55>;
+
 		status = "disabled";
 
 		pcieport0: pcie@0 {
@@ -7317,6 +7320,9 @@ pcie1: pcie@1c10000 {
 		phys = <&pcie1_phy>;
 		phy-names = "pciephy";
 
+		eq-presets-8gts = /bits/ 16 <0x5555 0x5555 0x5555 0x5555>;
+		eq-presets-16gts = /bits/ 8 <0x55 0x55 0x55 0x55>;
+
 		status = "disabled";
 
 		pcie@0 {
-- 
2.34.1


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Re: [PATCH v2 1/2] PCI: qcom: Add equalization settings for 8.0 GT/s

[Konrad Dybcio]

On 6/11/25 12:03 PM, Ziyue Zhang wrote:
> Adding lane equalization setting for 8.0 GT/s to enhance link stability
> and fix AER correctable errors reported on some platforms (eg. SA8775P).
> 
> 8.0 GT/s and 16.0GT/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 GEN speeds by writing 00b, 01b
> to `RATE_SHADOW_SEL`.
> 
> Hence program equalization registers in a loop using link speed as index,
> so that equalization setting can be programmed for both 8.0 GT/s and
> 16.0 GT/s.
> 
> 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 <quic_ziyuzhan@quicinc.com>
> ---

[...]

> -void qcom_pcie_common_set_16gt_equalization(struct dw_pcie *pci)
> +void qcom_pcie_common_set_equalization(struct dw_pcie *pci)
>  {
>  	u32 reg;
> +	u16 speed, max_speed = PCIE_SPEED_16_0GT;
> +	struct device *dev = pci->dev;
>  
>  	/*
>  	 * GEN3_RELATED_OFF register is repurposed to apply equalization
> @@ -18,33 +20,43 @@ void qcom_pcie_common_set_16gt_equalization(struct dw_pcie *pci)
>  	 * GEN3_EQ_*. The RATE_SHADOW_SEL bit field of GEN3_RELATED_OFF
>  	 * determines the data rate for which these equalization settings are
>  	 * applied.
> +	 *
> +	 * TODO:
> +	 * EQ settings need to be added for 32.0 T/s in future
>  	 */
> -	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);
> +	if (pcie_link_speed[pci->max_link_speed] < PCIE_SPEED_32_0GT)
> +		max_speed = pcie_link_speed[pci->max_link_speed];
> +	else
> +		dev_warn(dev, "The target supports 32.0 GT/s, but the EQ setting for 32.0 GT/s is not configured.\n");
>  
> -	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 <= max_speed; ++speed) {
> +		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_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_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);
> +	}

this function could receive `speed` as a parameter instead, so that
it's easier to parse

Konrad

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Re: [PATCH v2 2/2] arm64: dts: qcom: sa8775p: Add PCIe lane equalization preset properties

[Konrad Dybcio]

On 6/11/25 12:03 PM, Ziyue Zhang wrote:
> Add PCIe lane equalization preset properties with all values set to 5 for
> 8.0 GT/s and 16.0 GT/s data rates to enhance link stability.
> 
> 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 <quic_ziyuzhan@quicinc.com>
> ---

Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

Konrad

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Re: [PATCH v2 1/2] PCI: qcom: Add equalization settings for 8.0 GT/s

[Bjorn Helgaas]

On Wed, Jun 11, 2025 at 06:03:18PM +0800, Ziyue Zhang wrote:
> Adding lane equalization setting for 8.0 GT/s to enhance link stability
> and fix AER correctable errors reported on some platforms (eg. SA8775P).

s/Adding/Add/

s/fix AER correctable errors/avoid AER Correctable Errors/
so we know that (a) this avoids the errors (it's not some kind of
recovery), and (b) readers know that "Correctable Error" is something
that can be looked up in a spec.

> 8.0 GT/s and 16.0GT/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 GEN speeds by writing 00b, 01b
> to `RATE_SHADOW_SEL`.

s|16.0GT/s|16.0 GT/s| to match "8.0 GT/s"

s/different GEN speeds/different speeds/ (PCIe spec rev ("GEN") is not
a one-to-one mapping to speeds)

> @@ -18,33 +20,43 @@ void qcom_pcie_common_set_16gt_equalization(struct dw_pcie *pci)
>  	 * GEN3_EQ_*. The RATE_SHADOW_SEL bit field of GEN3_RELATED_OFF
>  	 * determines the data rate for which these equalization settings are
>  	 * applied.
> +	 *
> +	 * TODO:
> +	 * EQ settings need to be added for 32.0 T/s in future

Drop this comment since it's not an indication of a problem in this
patch.  The list of possible future work is infinite, and you can keep
track of a TODO list internally.

>  	 */
> -	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);
> +	if (pcie_link_speed[pci->max_link_speed] < PCIE_SPEED_32_0GT)
> +		max_speed = pcie_link_speed[pci->max_link_speed];
> +	else
> +		dev_warn(dev, "The target supports 32.0 GT/s, but the EQ setting for 32.0 GT/s is not configured.\n");

Drop period at end of message.

> -	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 <= max_speed; ++speed) {
> +		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_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_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);

Is "CUSROR" a typo for "CURSOR", or is "CUSROR" a real thing?  (Either
way, it's not something you added, so not a problem with this patch.)

Bjorn

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Re: [PATCH v2 1/2] PCI: qcom: Add equalization settings for 8.0 GT/s

[Ziyue Zhang]

On 6/11/2025 11:31 PM, Konrad Dybcio wrote:
> On 6/11/25 12:03 PM, Ziyue Zhang wrote:
>> Adding lane equalization setting for 8.0 GT/s to enhance link stability
>> and fix AER correctable errors reported on some platforms (eg. SA8775P).
>>
>> 8.0 GT/s and 16.0GT/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 GEN speeds by writing 00b, 01b
>> to `RATE_SHADOW_SEL`.
>>
>> Hence program equalization registers in a loop using link speed as index,
>> so that equalization setting can be programmed for both 8.0 GT/s and
>> 16.0 GT/s.
>>
>> 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 <quic_ziyuzhan@quicinc.com>
>> ---
> [...]
>
>> -void qcom_pcie_common_set_16gt_equalization(struct dw_pcie *pci)
>> +void qcom_pcie_common_set_equalization(struct dw_pcie *pci)
>>   {
>>   	u32 reg;
>> +	u16 speed, max_speed = PCIE_SPEED_16_0GT;
>> +	struct device *dev = pci->dev;
>>   
>>   	/*
>>   	 * GEN3_RELATED_OFF register is repurposed to apply equalization
>> @@ -18,33 +20,43 @@ void qcom_pcie_common_set_16gt_equalization(struct dw_pcie *pci)
>>   	 * GEN3_EQ_*. The RATE_SHADOW_SEL bit field of GEN3_RELATED_OFF
>>   	 * determines the data rate for which these equalization settings are
>>   	 * applied.
>> +	 *
>> +	 * TODO:
>> +	 * EQ settings need to be added for 32.0 T/s in future
>>   	 */
>> -	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);
>> +	if (pcie_link_speed[pci->max_link_speed] < PCIE_SPEED_32_0GT)
>> +		max_speed = pcie_link_speed[pci->max_link_speed];
>> +	else
>> +		dev_warn(dev, "The target supports 32.0 GT/s, but the EQ setting for 32.0 GT/s is not configured.\n");
>>   
>> -	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 <= max_speed; ++speed) {
>> +		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_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_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);
>> +	}
> this function could receive `speed` as a parameter instead, so that
> it's easier to parse
>
> Konrad

Hi Konrad,

On the current platform, the register write configurations for both
8.0 GT/s and 16.0 GT/s are identical, so we believe it's unnecessary to
pass ‘speed’ as a parameter at this stage.

However, I agree that if future platforms or speed modes introduce
configuration differences, it would make sense to revisit this and
consider adding speed as a parameter for better flexibility.

BRs
Ziyue


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Re: [PATCH v2 1/2] PCI: qcom: Add equalization settings for 8.0 GT/s

[Manivannan Sadhasivam]

On Wed, Jun 11, 2025 at 06:03:18PM +0800, Ziyue Zhang wrote:
> Adding lane equalization setting for 8.0 GT/s to enhance link stability
> and fix AER correctable errors reported on some platforms (eg. SA8775P).
> 
> 8.0 GT/s and 16.0GT/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 GEN speeds by writing 00b, 01b
> to `RATE_SHADOW_SEL`.
> 
> Hence program equalization registers in a loop using link speed as index,
> so that equalization setting can be programmed for both 8.0 GT/s and
> 16.0 GT/s.
> 
> 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 <quic_ziyuzhan@quicinc.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware.h  |  1 -
>  drivers/pci/controller/dwc/pcie-qcom-common.c | 60 +++++++++++--------
>  drivers/pci/controller/dwc/pcie-qcom-common.h |  2 +-
>  drivers/pci/controller/dwc/pcie-qcom-ep.c     |  6 +-
>  drivers/pci/controller/dwc/pcie-qcom.c        |  6 +-
>  5 files changed, 43 insertions(+), 32 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index ce9e18554e42..388306991467 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -127,7 +127,6 @@
>  #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)
> diff --git a/drivers/pci/controller/dwc/pcie-qcom-common.c b/drivers/pci/controller/dwc/pcie-qcom-common.c
> index 3aad19b56da8..4ff97ec13818 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom-common.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom-common.c
> @@ -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)
>  {
>  	u32 reg;
> +	u16 speed, max_speed = PCIE_SPEED_16_0GT;
> +	struct device *dev = pci->dev;
>  
>  	/*
>  	 * GEN3_RELATED_OFF register is repurposed to apply equalization
> @@ -18,33 +20,43 @@ void qcom_pcie_common_set_16gt_equalization(struct dw_pcie *pci)
>  	 * GEN3_EQ_*. The RATE_SHADOW_SEL bit field of GEN3_RELATED_OFF
>  	 * determines the data rate for which these equalization settings are
>  	 * applied.
> +	 *
> +	 * TODO:
> +	 * EQ settings need to be added for 32.0 T/s in future
>  	 */
> -	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);
> +	if (pcie_link_speed[pci->max_link_speed] < PCIE_SPEED_32_0GT)
> +		max_speed = pcie_link_speed[pci->max_link_speed];
> +	else
> +		dev_warn(dev, "The target supports 32.0 GT/s, but the EQ setting for 32.0 GT/s is not configured.\n");

I believe the warning is enough to inform the users/developers that the driver
update is needed. So the TODO above looks redundant.

- Mani

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Re: [PATCH v2 2/2] arm64: dts: qcom: sa8775p: Add PCIe lane equalization preset properties

[Manivannan Sadhasivam]

On Wed, Jun 11, 2025 at 06:03:19PM +0800, Ziyue Zhang wrote:
> Add PCIe lane equalization preset properties with all values set to 5 for
> 8.0 GT/s and 16.0 GT/s data rates to enhance link stability.
> 
> 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 <quic_ziyuzhan@quicinc.com>

Acked-by: Manivannan Sadhasivam <mani@kernel.org>

- Mani

> ---
>  arch/arm64/boot/dts/qcom/sa8775p.dtsi | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sa8775p.dtsi b/arch/arm64/boot/dts/qcom/sa8775p.dtsi
> index 45f536633f64..16caf1da0708 100644
> --- a/arch/arm64/boot/dts/qcom/sa8775p.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sa8775p.dtsi
> @@ -7159,6 +7159,9 @@ pcie0: pcie@1c00000 {
>  		phys = <&pcie0_phy>;
>  		phy-names = "pciephy";
>  
> +		eq-presets-8gts = /bits/ 16 <0x5555 0x5555>;
> +		eq-presets-16gts = /bits/ 8 <0x55 0x55>;
> +
>  		status = "disabled";
>  
>  		pcieport0: pcie@0 {
> @@ -7317,6 +7320,9 @@ pcie1: pcie@1c10000 {
>  		phys = <&pcie1_phy>;
>  		phy-names = "pciephy";
>  
> +		eq-presets-8gts = /bits/ 16 <0x5555 0x5555 0x5555 0x5555>;
> +		eq-presets-16gts = /bits/ 8 <0x55 0x55 0x55 0x55>;
> +
>  		status = "disabled";
>  
>  		pcie@0 {
> -- 
> 2.34.1
> 

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