[PATCH V6 0/4] Add DT-based gear and rate limiting support

[PATCH V6 0/4] Add DT-based gear and rate limiting support

[Ram Kumar Dwivedi]

This patch series adds support for limiting the maximum high-speed
gear and rate used by the UFS controller via device tree properties.

Some platforms may have signal integrity, clock configuration, or
layout issues that prevent reliable operation at higher gears or rates.
This is especially critical in automotive and other platforms where
stability is prioritized over peak performance.

The series follows this logical progression:
1. Document the new DT properties in the common UFS binding
2. Clean up existing redundant code in the qcom driver
3. Add platform-level parsing support for the new properties
4. Integrate the platform support in the qcom driver

This approach makes the functionality available to other UFS host
drivers and provides a cleaner, more maintainable implementation.

Changes from V1: 
- Restructured patch series for better logical flow and maintainability.
- Moved DT bindings to ufs-common.yaml making it available for all UFS 
  controllers.
- Added platform-level support in ufshcd-pltfrm.c for code reusability.
- Separated the cleanup patch to remove redundant hs_rate assignment in
  qcom driver.
- Removed SA8155 DTS changes to keep the series focused on core
  functionality.
- Improved commit messages with better technical rationale.

Changes from V2: 
- Documented default values of limit-rate and limit-hs-gear in DT bindings
  as per Krzysztof's suggestion.

Changes from V3: 
- Changed limit-rate property from numeric values 1 and 2 to string values
  Rate-A and Rate-B for better readability and clarity as suggested by
  Bart and Krzysztof.
- Added Co-developed-by tag for Nitin Rawat in 3rd patch. 

Changes from V4:
- Added the missing argument to the error message while parsing
  limit-rate property.
- Updated the maximum supported value and default for limit-gear
  property to gear 6, as per Krzysztof's and Bart's recommendation.
- Renamed Rate-A and Rate-B to lowercase (rate-a, rate-b) as suggested
  by Krzysztof.

Changes from V5:
- Updated device tree property name from "limit-rate" to "limit-gear-rate"
  to improve clarity and consistency as suggested by Alim Akhtar.
- Renamed function ufshcd_parse_limits() to ufshcd_parse_gear_limits()
  for better alignment with its purpose as suggested by Alim Akhtar.
- Renamed function ufs_qcom_parse_limit() to ufs_qcom_parse_gear_limit()
  for consistency with naming conventions.
- Added Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com> to patch 2/4.
- Added Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org> to patch 1/4.

Ram Kumar Dwivedi (4):
  ufs: dt-bindings: Document gear and rate limit properties
  ufs: ufs-qcom: Remove redundant re-assignment to hs_rate
  ufs: pltfrm: Add DT support to limit HS gear and gear rate
  ufs: ufs-qcom: Add support for limiting HS gear and rate

 .../devicetree/bindings/ufs/ufs-common.yaml   | 16 +++++++++
 drivers/ufs/host/ufs-qcom.c                   | 21 ++++++++----
 drivers/ufs/host/ufshcd-pltfrm.c              | 33 +++++++++++++++++++
 drivers/ufs/host/ufshcd-pltfrm.h              |  1 +
 4 files changed, 65 insertions(+), 6 deletions(-)

-- 
2.50.1

[PATCH V6 1/4] ufs: dt-bindings: Document gear and rate limit properties

[Ram Kumar Dwivedi]

Add optional "limit-hs-gear" and "limit-rate" properties to the
UFS controller common binding. These properties allow limiting
the maximum HS gear and rate.

This is useful in cases where the customer board may have signal
integrity, clock configuration or layout issues that prevent reliable
operation at higher gears. Such limitations are especially critical in
those platforms, where stability is prioritized over peak performance.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Ram Kumar Dwivedi <quic_rdwivedi@quicinc.com>
---
 .../devicetree/bindings/ufs/ufs-common.yaml      | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/Documentation/devicetree/bindings/ufs/ufs-common.yaml b/Documentation/devicetree/bindings/ufs/ufs-common.yaml
index 31fe7f30ff5b..9f04f34d8c5a 100644
--- a/Documentation/devicetree/bindings/ufs/ufs-common.yaml
+++ b/Documentation/devicetree/bindings/ufs/ufs-common.yaml
@@ -89,6 +89,22 @@ properties:
 
   msi-parent: true
 
+  limit-hs-gear:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 1
+    maximum: 6
+    default: 6
+    description:
+      Restricts the maximum HS gear used in both TX and RX directions.
+
+  limit-gear-rate:
+    $ref: /schemas/types.yaml#/definitions/string
+    enum: [rate-a, rate-b]
+    default: rate-b
+    description:
+      Restricts the UFS controller to rate-a or rate-b for both TX and
+      RX directions.
+
 dependencies:
   freq-table-hz: [ clocks ]
   operating-points-v2: [ clocks, clock-names ]
-- 
2.50.1

[PATCH V6 2/4] ufs: ufs-qcom: Remove redundant re-assignment to hs_rate

[Ram Kumar Dwivedi]

Remove the redundant else block that assigns PA_HS_MODE_B to hs_rate,
as it is already assigned in ufshcd_init_host_params(). This avoids
unnecessary reassignment and prevents overwriting hs_rate when it is
explicitly set to a different value.

Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Ram Kumar Dwivedi <quic_rdwivedi@quicinc.com>
---
 drivers/ufs/host/ufs-qcom.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
index 9574fdc2bb0f..1a93351fb70e 100644
--- a/drivers/ufs/host/ufs-qcom.c
+++ b/drivers/ufs/host/ufs-qcom.c
@@ -494,12 +494,8 @@ static int ufs_qcom_power_up_sequence(struct ufs_hba *hba)
 	 * If the HS-G5 PHY gear is used, update host_params->hs_rate to Rate-A,
 	 * so that the subsequent power mode change shall stick to Rate-A.
 	 */
-	if (host->hw_ver.major == 0x5) {
-		if (host->phy_gear == UFS_HS_G5)
-			host_params->hs_rate = PA_HS_MODE_A;
-		else
-			host_params->hs_rate = PA_HS_MODE_B;
-	}
+	if (host->hw_ver.major == 0x5 && host->phy_gear == UFS_HS_G5)
+		host_params->hs_rate = PA_HS_MODE_A;
 
 	mode = host_params->hs_rate == PA_HS_MODE_B ? PHY_MODE_UFS_HS_B : PHY_MODE_UFS_HS_A;
 
-- 
2.50.1

[PATCH V6 3/4] ufs: pltfrm: Add DT support to limit HS gear and gear rate

[Ram Kumar Dwivedi]

Introduce parsing of 'limit-hs-gear' and 'limit-gear-rate'
device tree properties to restrict high-speed gear and rate
during initialization.

This is useful in cases where the customer board may have
signal integrity, clock configuration or layout issues that
prevent reliable operation at higher gears. Such limitations
are especially critical in those platforms, where stability
is prioritized over peak performance.

Co-developed-by: Nitin Rawat <quic_nitirawa@quicinc.com>
Signed-off-by: Nitin Rawat <quic_nitirawa@quicinc.com>
Signed-off-by: Ram Kumar Dwivedi <quic_rdwivedi@quicinc.com>
---
 drivers/ufs/host/ufshcd-pltfrm.c | 33 ++++++++++++++++++++++++++++++++
 drivers/ufs/host/ufshcd-pltfrm.h |  1 +
 2 files changed, 34 insertions(+)

diff --git a/drivers/ufs/host/ufshcd-pltfrm.c b/drivers/ufs/host/ufshcd-pltfrm.c
index ffe5d1d2b215..c2dafb583cf5 100644
--- a/drivers/ufs/host/ufshcd-pltfrm.c
+++ b/drivers/ufs/host/ufshcd-pltfrm.c
@@ -430,6 +430,39 @@ int ufshcd_negotiate_pwr_params(const struct ufs_host_params *host_params,
 }
 EXPORT_SYMBOL_GPL(ufshcd_negotiate_pwr_params);
 
+/**
+ * ufshcd_parse_gear_limits - Parse DT-based gear and rate limits for UFS
+ * @hba: Pointer to UFS host bus adapter instance
+ * @host_params: Pointer to UFS host parameters structure to be updated
+ *
+ * This function reads optional device tree properties to apply
+ * platform-specific constraints.
+ *
+ * "limit-hs-gear": Specifies the max HS gear.
+ * "limit-gear-rate": Specifies the max High-Speed rate.
+ */
+void ufshcd_parse_gear_limits(struct ufs_hba *hba, struct ufs_host_params *host_params)
+{
+	struct device_node *np = hba->dev->of_node;
+	u32 hs_gear;
+	const char *hs_rate;
+
+	if (!of_property_read_u32(np, "limit-hs-gear", &hs_gear)) {
+		host_params->hs_tx_gear = hs_gear;
+		host_params->hs_rx_gear = hs_gear;
+	}
+
+	if (!of_property_read_string(np, "limit-gear-rate", &hs_rate)) {
+		if (!strcmp(hs_rate, "rate-a"))
+			host_params->hs_rate = PA_HS_MODE_A;
+		else if (!strcmp(hs_rate, "rate-b"))
+			host_params->hs_rate = PA_HS_MODE_B;
+		else
+			dev_warn(hba->dev, "Invalid rate: %s\n", hs_rate);
+	}
+}
+EXPORT_SYMBOL_GPL(ufshcd_parse_gear_limits);
+
 void ufshcd_init_host_params(struct ufs_host_params *host_params)
 {
 	*host_params = (struct ufs_host_params){
diff --git a/drivers/ufs/host/ufshcd-pltfrm.h b/drivers/ufs/host/ufshcd-pltfrm.h
index 3017f8e8f93c..0a18a8aed94d 100644
--- a/drivers/ufs/host/ufshcd-pltfrm.h
+++ b/drivers/ufs/host/ufshcd-pltfrm.h
@@ -29,6 +29,7 @@ int ufshcd_negotiate_pwr_params(const struct ufs_host_params *host_params,
 				const struct ufs_pa_layer_attr *dev_max,
 				struct ufs_pa_layer_attr *agreed_pwr);
 void ufshcd_init_host_params(struct ufs_host_params *host_params);
+void ufshcd_parse_gear_limits(struct ufs_hba *hba, struct ufs_host_params *host_params);
 int ufshcd_pltfrm_init(struct platform_device *pdev,
 		       const struct ufs_hba_variant_ops *vops);
 void ufshcd_pltfrm_remove(struct platform_device *pdev);
-- 
2.50.1

[PATCH V6 4/4] ufs: ufs-qcom: Add support for limiting HS gear and rate

[Ram Kumar Dwivedi]

Add support to limit Tx/Rx gear and rate during UFS initialization
based on DT property.

Also update the phy_gear to ensure PHY calibrations align with
the required gear and rate.

Signed-off-by: Ram Kumar Dwivedi <quic_rdwivedi@quicinc.com>
---
 drivers/ufs/host/ufs-qcom.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
index 1a93351fb70e..b5d7904597d9 100644
--- a/drivers/ufs/host/ufs-qcom.c
+++ b/drivers/ufs/host/ufs-qcom.c
@@ -1092,6 +1092,18 @@ static void ufs_qcom_set_phy_gear(struct ufs_qcom_host *host)
 	}
 }
 
+static void ufs_qcom_parse_gear_limits(struct ufs_hba *hba)
+{
+	struct ufs_qcom_host *host = ufshcd_get_variant(hba);
+	struct ufs_host_params *host_params = &host->host_params;
+	u32 hs_gear_old = host_params->hs_tx_gear;
+
+	ufshcd_parse_gear_limits(hba, host_params);
+	if (host_params->hs_tx_gear != hs_gear_old) {
+		host->phy_gear = host_params->hs_tx_gear;
+	}
+}
+
 static void ufs_qcom_set_host_params(struct ufs_hba *hba)
 {
 	struct ufs_qcom_host *host = ufshcd_get_variant(hba);
@@ -1333,6 +1345,7 @@ static int ufs_qcom_init(struct ufs_hba *hba)
 	ufs_qcom_advertise_quirks(hba);
 	ufs_qcom_set_host_params(hba);
 	ufs_qcom_set_phy_gear(host);
+	ufs_qcom_parse_gear_limits(hba);
 
 	err = ufs_qcom_ice_init(host);
 	if (err)
-- 
2.50.1

RE: [PATCH V6 1/4] ufs: dt-bindings: Document gear and rate limit properties

[Alim Akhtar]

> -----Original Message-----
> From: Ram Kumar Dwivedi <quic_rdwivedi@quicinc.com>
> Sent: Wednesday, September 17, 2025 7:40 PM
> To: alim.akhtar@samsung.com; avri.altman@wdc.com; bvanassche@acm.org;
> robh@kernel.org; krzk+dt@kernel.org; conor+dt@kernel.org; mani@kernel.org;
> James.Bottomley@HansenPartnership.com; martin.petersen@oracle.com
> Cc: linux-scsi@vger.kernel.org; devicetree@vger.kernel.org; linux-
> kernel@vger.kernel.org; linux-arm-msm@vger.kernel.org; Krzysztof Kozlowski
> <krzysztof.kozlowski@linaro.org>
> Subject: [PATCH V6 1/4] ufs: dt-bindings: Document gear and rate limit
> properties
> 
> Add optional "limit-hs-gear" and "limit-rate" properties to the UFS
controller
> common binding. These properties allow limiting the maximum HS gear and
rate.
> 
> This is useful in cases where the customer board may have signal
integrity, clock
> configuration or layout issues that prevent reliable operation at higher
gears.
> Such limitations are especially critical in those platforms, where
stability is
> prioritized over peak performance.
> 
> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> Signed-off-by: Ram Kumar Dwivedi <quic_rdwivedi@quicinc.com>
> ---
Thanks!
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>

RE: [PATCH V6 3/4] ufs: pltfrm: Add DT support to limit HS gear and gear rate

[Alim Akhtar]

> -----Original Message-----
> From: Ram Kumar Dwivedi <quic_rdwivedi@quicinc.com>
> Sent: Wednesday, September 17, 2025 7:40 PM
> To: alim.akhtar@samsung.com; avri.altman@wdc.com; bvanassche@acm.org;
> robh@kernel.org; krzk+dt@kernel.org; conor+dt@kernel.org; mani@kernel.org;
> James.Bottomley@HansenPartnership.com; martin.petersen@oracle.com
> Cc: linux-scsi@vger.kernel.org; devicetree@vger.kernel.org; linux-
> kernel@vger.kernel.org; linux-arm-msm@vger.kernel.org; Nitin Rawat
> <quic_nitirawa@quicinc.com>
> Subject: [PATCH V6 3/4] ufs: pltfrm: Add DT support to limit HS gear and
gear
> rate
> 
> Introduce parsing of 'limit-hs-gear' and 'limit-gear-rate'
> device tree properties to restrict high-speed gear and rate during
initialization.
> 
> This is useful in cases where the customer board may have signal
integrity, clock
> configuration or layout issues that prevent reliable operation at higher
gears.
> Such limitations are especially critical in those platforms, where
stability is
> prioritized over peak performance.
> 
> Co-developed-by: Nitin Rawat <quic_nitirawa@quicinc.com>
> Signed-off-by: Nitin Rawat <quic_nitirawa@quicinc.com>
> Signed-off-by: Ram Kumar Dwivedi <quic_rdwivedi@quicinc.com>
> ---

Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>

RE: [PATCH V6 4/4] ufs: ufs-qcom: Add support for limiting HS gear and rate

[Alim Akhtar]

> -----Original Message-----
> From: Ram Kumar Dwivedi <quic_rdwivedi@quicinc.com>
> Sent: Wednesday, September 17, 2025 7:40 PM
> To: alim.akhtar@samsung.com; avri.altman@wdc.com; bvanassche@acm.org;
> robh@kernel.org; krzk+dt@kernel.org; conor+dt@kernel.org; mani@kernel.org;
> James.Bottomley@HansenPartnership.com; martin.petersen@oracle.com
> Cc: linux-scsi@vger.kernel.org; devicetree@vger.kernel.org; linux-
> kernel@vger.kernel.org; linux-arm-msm@vger.kernel.org
> Subject: [PATCH V6 4/4] ufs: ufs-qcom: Add support for limiting HS gear
and rate
> 
> Add support to limit Tx/Rx gear and rate during UFS initialization based
on DT
> property.
> 
> Also update the phy_gear to ensure PHY calibrations align with the
required gear
> and rate.
> 
> Signed-off-by: Ram Kumar Dwivedi <quic_rdwivedi@quicinc.com>
> ---

Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>

Re: [PATCH V6 0/4] Add DT-based gear and rate limiting support

[Martin K. Petersen]

Ram,

> This patch series adds support for limiting the maximum high-speed
> gear and rate used by the UFS controller via device tree properties.

Applied to 6.18/scsi-staging, thanks!

-- 
Martin K. Petersen