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..4df6885f0dc0 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: %s\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

> -----Original Message-----
> From: Ram Kumar Dwivedi <quic_rdwivedi@quicinc.com>
> Sent: Tuesday, September 2, 2025 10:19 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 V5 3/4] ufs: pltfrm: Allow limiting HS gear and rate via
DT
> 
> 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..4df6885f0dc0 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

May be s/ufshcd_parse_limits/ ufshcd_parse_gear_limits()

"Limits" is very generic and also not aligning with the property names.
Also suggest to change limit-rate to limit-gear-rate.

> +*host_params) {
> +	struct device_node *np = hba->dev->of_node;
> +	u32 hs_gear;
> +	const char *hs_rate;
> +
> +	if (!np)
> +		return;
Probably a overkill here, please check if this will ever hit? 

> +
> +	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: %s\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

On 03-Sep-25 9:58 AM, Alim Akhtar wrote:
> 
> 
>> -----Original Message-----
>> From: Ram Kumar Dwivedi <quic_rdwivedi@quicinc.com>
>> Sent: Tuesday, September 2, 2025 10:19 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 V5 3/4] ufs: pltfrm: Allow limiting HS gear and rate via
> DT
>>
>> 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..4df6885f0dc0 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
> 
> May be s/ufshcd_parse_limits/ ufshcd_parse_gear_limits()
> 
> "Limits" is very generic and also not aligning with the property names.
> Also suggest to change limit-rate to limit-gear-rate.

Hi Alim,

I have addressed this in next patchset.

> 
>> +*host_params) {
>> +	struct device_node *np = hba->dev->of_node;
>> +	u32 hs_gear;
>> +	const char *hs_rate;
>> +
>> +	if (!np)
>> +		return;
> Probably a overkill here, please check if this will ever hit? 

I have addressed this in next patchset.

> 
>> +
>> +	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: %s\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
> 
>