[PATCH V4 0/4] Add DT-based gear and rate limiting support

[PATCH V4 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. 

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: Allow limiting HS gear and rate via DT
  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              | 36 +++++++++++++++++++
 drivers/ufs/host/ufshcd-pltfrm.h              |  1 +
 4 files changed, 68 insertions(+), 6 deletions(-)

-- 
2.50.1

[PATCH V4 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.

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..b4c99fee552f 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: 5
+    default: 5
+    description:
+      Restricts the maximum HS gear used in both TX and RX directions.
+
+  limit-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 V4 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.

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 V4 3/4] ufs: pltfrm: Allow limiting HS gear and rate via DT

[Ram Kumar Dwivedi]

Add support for parsing 'limit-hs-gear' and 'limit-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 | 36 ++++++++++++++++++++++++++++++++
 drivers/ufs/host/ufshcd-pltfrm.h |  1 +
 2 files changed, 37 insertions(+)

diff --git a/drivers/ufs/host/ufshcd-pltfrm.c b/drivers/ufs/host/ufshcd-pltfrm.c
index ffe5d1d2b215..a3cfb1935bbc 100644
--- a/drivers/ufs/host/ufshcd-pltfrm.c
+++ b/drivers/ufs/host/ufshcd-pltfrm.c
@@ -430,6 +430,42 @@ int ufshcd_negotiate_pwr_params(const struct ufs_host_params *host_params,
 }
 EXPORT_SYMBOL_GPL(ufshcd_negotiate_pwr_params);
 
+/**
+ * ufshcd_parse_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-rate": Specifies the max High-Speed rate.
+ */
+void ufshcd_parse_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 (!np)
+		return;
+
+	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-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 limit-rate value\n", hs_rate);
+	}
+}
+EXPORT_SYMBOL_GPL(ufshcd_parse_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..1617f2541273 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_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 V4 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..53c64d5fb95d 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_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_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_limits(hba);
 
 	err = ufs_qcom_ice_init(host);
 	if (err)
-- 
2.50.1

Re: [PATCH V4 3/4] ufs: pltfrm: Allow limiting HS gear and rate via DT

[kernel test robot]

Hi Ram,

kernel test robot noticed the following build warnings:

[auto build test WARNING on mkp-scsi/for-next]
[also build test WARNING on jejb-scsi/for-next robh/for-next linus/master v6.17-rc4 next-20250901]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Ram-Kumar-Dwivedi/ufs-dt-bindings-Document-gear-and-rate-limit-properties/20250902-000038
base:   https://git.kernel.org/pub/scm/linux/kernel/git/mkp/scsi.git for-next
patch link:    https://lore.kernel.org/r/20250901155801.26988-4-quic_rdwivedi%40quicinc.com
patch subject: [PATCH V4 3/4] ufs: pltfrm: Allow limiting HS gear and rate via DT
config: arc-randconfig-002-20250902 (https://download.01.org/0day-ci/archive/20250902/202509021257.jIDXzoS6-lkp@intel.com/config)
compiler: arc-linux-gcc (GCC) 9.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250902/202509021257.jIDXzoS6-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202509021257.jIDXzoS6-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from include/linux/device.h:15,
                    from include/linux/platform_device.h:13,
                    from drivers/ufs/host/ufshcd-pltfrm.c:13:
   drivers/ufs/host/ufshcd-pltfrm.c: In function 'ufshcd_parse_limits':
>> drivers/ufs/host/ufshcd-pltfrm.c:464:23: warning: too many arguments for format [-Wformat-extra-args]
     464 |    dev_warn(hba->dev, "Invalid limit-rate value\n", hs_rate);
         |                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/dev_printk.h:110:16: note: in definition of macro 'dev_printk_index_wrap'
     110 |   _p_func(dev, fmt, ##__VA_ARGS__);   \
         |                ^~~
   include/linux/dev_printk.h:156:54: note: in expansion of macro 'dev_fmt'
     156 |  dev_printk_index_wrap(_dev_warn, KERN_WARNING, dev, dev_fmt(fmt), ##__VA_ARGS__)
         |                                                      ^~~~~~~
   drivers/ufs/host/ufshcd-pltfrm.c:464:4: note: in expansion of macro 'dev_warn'
     464 |    dev_warn(hba->dev, "Invalid limit-rate value\n", hs_rate);
         |    ^~~~~~~~


vim +464 drivers/ufs/host/ufshcd-pltfrm.c

   432	
   433	/**
   434	 * ufshcd_parse_limits - Parse DT-based gear and rate limits for UFS
   435	 * @hba: Pointer to UFS host bus adapter instance
   436	 * @host_params: Pointer to UFS host parameters structure to be updated
   437	 *
   438	 * This function reads optional device tree properties to apply
   439	 * platform-specific constraints.
   440	 *
   441	 * "limit-hs-gear": Specifies the max HS gear.
   442	 * "limit-rate": Specifies the max High-Speed rate.
   443	 */
   444	void ufshcd_parse_limits(struct ufs_hba *hba, struct ufs_host_params *host_params)
   445	{
   446		struct device_node *np = hba->dev->of_node;
   447		u32 hs_gear;
   448		const char *hs_rate;
   449	
   450		if (!np)
   451			return;
   452	
   453		if (!of_property_read_u32(np, "limit-hs-gear", &hs_gear)) {
   454			host_params->hs_tx_gear = hs_gear;
   455			host_params->hs_rx_gear = hs_gear;
   456		}
   457	
   458		if (!of_property_read_string(np, "limit-rate", &hs_rate)) {
   459			if (!strcmp(hs_rate, "Rate-A"))
   460				host_params->hs_rate = PA_HS_MODE_A;
   461			else if (!strcmp(hs_rate, "Rate-B"))
   462				host_params->hs_rate = PA_HS_MODE_B;
   463			else
 > 464				dev_warn(hba->dev, "Invalid limit-rate value\n", hs_rate);
   465		}
   466	}
   467	EXPORT_SYMBOL_GPL(ufshcd_parse_limits);
   468	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH V4 1/4] ufs: dt-bindings: Document gear and rate limit properties

[Krzysztof Kozlowski]

On 01/09/2025 17:57, Ram Kumar Dwivedi wrote:
> 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.
> 
> 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..b4c99fee552f 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: 5

No improvements.

> +    default: 5
> +    description:
> +      Restricts the maximum HS gear used in both TX and RX directions.
> +
> +  limit-rate:
> +    $ref: /schemas/types.yaml#/definitions/string
> +    enum: [Rate-A, Rate-B]

lowercase

> +    default: Rate-B


Best regards,
Krzysztof

Re: [PATCH V4 1/4] ufs: dt-bindings: Document gear and rate limit properties

[Ram Kumar Dwivedi]

On 02-Sep-25 11:42 AM, Krzysztof Kozlowski wrote:
> On 01/09/2025 17:57, Ram Kumar Dwivedi wrote:
>> 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.
>>
>> 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..b4c99fee552f 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: 5
> 
> No improvements.

Hi Krzysztof,

I have updated it in the next patchset.

Thanks,
Ram.> 
>> +    default: 5
>> +    description:
>> +      Restricts the maximum HS gear used in both TX and RX directions.
>> +
>> +  limit-rate:
>> +    $ref: /schemas/types.yaml#/definitions/string
>> +    enum: [Rate-A, Rate-B]
> 
> lowercase
I have updated it in the next patchset.

Thanks,
Ram.> 
>> +    default: Rate-B
> 
> 
> Best regards,
> Krzysztof