[PATCH V1 0/3] Add support to disable UFS LPM

[PATCH V1 0/3] Add support to disable UFS LPM

[Nitin Rawat]

Add support to disable UFS Low Power Mode (LPM) for platforms
that doesn't support LPM.

Nitin Rawat (3):
  scsi: ufs: dt-bindings: Document UFS Disable LPM property
  scsi: ufs: pltfrm: Add parsing support for disable LPM property
  scsi: ufs: qcom: Add support to disable UFS LPM Feature

 .../devicetree/bindings/ufs/ufs-common.yaml       |  5 +++++
 drivers/ufs/host/ufs-qcom.c                       | 15 ++++++++-------
 drivers/ufs/host/ufshcd-pltfrm.c                  | 15 +++++++++++++++
 include/ufs/ufshcd.h                              |  1 +
 4 files changed, 29 insertions(+), 7 deletions(-)

--
2.48.1

[PATCH V1 1/3] scsi: ufs: dt-bindings: Document UFS Disable LPM property

[Nitin Rawat]

Disable UFS low power mode on emulation FPGA platforms or other platforms
where it is either unsupported or power efficiency is not a critical
requirement.

Document the UFS Disable LPM property for such platforms.

Signed-off-by: Nitin Rawat <quic_nitirawa@quicinc.com>
---
 Documentation/devicetree/bindings/ufs/ufs-common.yaml | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/devicetree/bindings/ufs/ufs-common.yaml b/Documentation/devicetree/bindings/ufs/ufs-common.yaml
index 31fe7f30ff5b..eab28beb0e76 100644
--- a/Documentation/devicetree/bindings/ufs/ufs-common.yaml
+++ b/Documentation/devicetree/bindings/ufs/ufs-common.yaml
@@ -89,6 +89,11 @@ properties:

   msi-parent: true

+  disable-lpm:
+    type: boolean
+    description:
+      Disable UFS LPM features.
+
 dependencies:
   freq-table-hz: [ clocks ]
   operating-points-v2: [ clocks, clock-names ]
--
2.48.1

[PATCH V1 2/3] scsi: ufs: pltfrm: Add parsing support for disable LPM property

[Nitin Rawat]

There are emulation FPGA platforms or other platforms where UFS low
power mode is either unsupported or power efficiency is not a critical
requirement.

Add support for parsing disable LPM property from device tree . The
disable lpm support in devicetree is added through the "disable-lpm"
property for such platforms.

Disabling LPM ensure stable operation and compatibility with these
environments, where power management features might interfere with
performance or functionality.

Signed-off-by: Nitin Rawat <quic_nitirawa@quicinc.com>
---
 drivers/ufs/host/ufshcd-pltfrm.c | 15 +++++++++++++++
 include/ufs/ufshcd.h             |  1 +
 2 files changed, 16 insertions(+)

diff --git a/drivers/ufs/host/ufshcd-pltfrm.c b/drivers/ufs/host/ufshcd-pltfrm.c
index ffe5d1d2b215..764525d9262b 100644
--- a/drivers/ufs/host/ufshcd-pltfrm.c
+++ b/drivers/ufs/host/ufshcd-pltfrm.c
@@ -210,6 +210,19 @@ static void ufshcd_init_lanes_per_dir(struct ufs_hba *hba)
 	}
 }

+/**
+ * ufshcd_parse_lpm_support - read from DT whether LPM modes should be disabled.
+ * @hba: host controller instance
+ */
+static void ufshcd_parse_lpm_support(struct ufs_hba *hba)
+{
+	struct device *dev = hba->dev;
+
+	hba->disable_lpm = of_property_read_bool(dev->of_node, "disable-lpm");
+	if (hba->disable_lpm)
+		dev_info(hba->dev, "UFS LPM is disabled\n");
+}
+
 /**
  * ufshcd_parse_clock_min_max_freq  - Parse MIN and MAX clocks freq
  * @hba: per adapter instance
@@ -495,6 +508,8 @@ int ufshcd_pltfrm_init(struct platform_device *pdev,

 	ufshcd_init_lanes_per_dir(hba);

+	ufshcd_parse_lpm_support(hba);
+
 	err = ufshcd_parse_operating_points(hba);
 	if (err) {
 		dev_err(dev, "%s: OPP parse failed %d\n", __func__, err);
diff --git a/include/ufs/ufshcd.h b/include/ufs/ufshcd.h
index e928ed0265ff..5a3daed1f086 100644
--- a/include/ufs/ufshcd.h
+++ b/include/ufs/ufshcd.h
@@ -1143,6 +1143,7 @@ struct ufs_hba {
 	int critical_health_count;
 	atomic_t dev_lvl_exception_count;
 	u64 dev_lvl_exception_id;
+	bool disable_lpm;
 };

 /**
--
2.48.1

[PATCH V1 3/3] scsi: ufs: qcom: Add support to disable UFS LPM Feature

[Nitin Rawat]

There are emulation FPGA platforms or other platforms where UFS low
power mode is either unsupported or power efficiency is not a critical
requirement.

Disable all low power mode UFS feature based on the "disable-lpm" device
tree property parsed in platform driver.

Signed-off-by: Nitin Rawat <quic_nitirawa@quicinc.com>
---
 drivers/ufs/host/ufs-qcom.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
index 1b37449fbffc..1024edf36b68 100644
--- a/drivers/ufs/host/ufs-qcom.c
+++ b/drivers/ufs/host/ufs-qcom.c
@@ -1014,13 +1014,14 @@ static void ufs_qcom_set_host_caps(struct ufs_hba *hba)

 static void ufs_qcom_set_caps(struct ufs_hba *hba)
 {
-	hba->caps |= UFSHCD_CAP_CLK_GATING | UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
-	hba->caps |= UFSHCD_CAP_CLK_SCALING | UFSHCD_CAP_WB_WITH_CLK_SCALING;
-	hba->caps |= UFSHCD_CAP_AUTO_BKOPS_SUSPEND;
-	hba->caps |= UFSHCD_CAP_WB_EN;
-	hba->caps |= UFSHCD_CAP_AGGR_POWER_COLLAPSE;
-	hba->caps |= UFSHCD_CAP_RPM_AUTOSUSPEND;
-
+	if (!hba->disable_lpm) {
+		hba->caps |= UFSHCD_CAP_CLK_GATING | UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
+		hba->caps |= UFSHCD_CAP_CLK_SCALING | UFSHCD_CAP_WB_WITH_CLK_SCALING;
+		hba->caps |= UFSHCD_CAP_AUTO_BKOPS_SUSPEND;
+		hba->caps |= UFSHCD_CAP_WB_EN;
+		hba->caps |= UFSHCD_CAP_AGGR_POWER_COLLAPSE;
+		hba->caps |= UFSHCD_CAP_RPM_AUTOSUSPEND;
+	}
 	ufs_qcom_set_host_caps(hba);
 }

--
2.48.1

Re: [PATCH V1 0/3] Add support to disable UFS LPM

[Bart Van Assche]

On 4/17/25 5:46 AM, Nitin Rawat wrote:
> Add support to disable UFS Low Power Mode (LPM) for platforms
> that doesn't support LPM.
This patch series looks good to me.

Thanks,

Bart.

Re: [PATCH V1 2/3] scsi: ufs: pltfrm: Add parsing support for disable LPM property

[Mukesh Kumar Savaliya]

On 4/17/2025 6:16 PM, Nitin Rawat wrote:
[...]
> +/**
> + * ufshcd_parse_lpm_support - read from DT whether LPM modes should be disabled.
> + * @hba: host controller instance
> + */
> +static void ufshcd_parse_lpm_support(struct ufs_hba *hba)
> +{
> +	struct device *dev = hba->dev;
> +
> +	hba->disable_lpm = of_property_read_bool(dev->of_node, "disable-lpm");
> +	if (hba->disable_lpm)
> +		dev_info(hba->dev, "UFS LPM is disabled\n");
How about keeping as debug ?
> +}
> +
[...]
> --
> 2.48.1
> 
> 

Re: [PATCH V1 2/3] scsi: ufs: pltfrm: Add parsing support for disable LPM property

[Rob Herring]

On Fri, Apr 18, 2025 at 10:13:46AM +0530, Mukesh Kumar Savaliya wrote:
> 
> 
> On 4/17/2025 6:16 PM, Nitin Rawat wrote:
> [...]
> > +/**
> > + * ufshcd_parse_lpm_support - read from DT whether LPM modes should be disabled.
> > + * @hba: host controller instance
> > + */
> > +static void ufshcd_parse_lpm_support(struct ufs_hba *hba)
> > +{
> > +	struct device *dev = hba->dev;
> > +
> > +	hba->disable_lpm = of_property_read_bool(dev->of_node, "disable-lpm");
> > +	if (hba->disable_lpm)
> > +		dev_info(hba->dev, "UFS LPM is disabled\n");
> How about keeping as debug ?

Why print it at all. You can just read the DT from userspace.

Rob

Re: [PATCH V1 3/3] scsi: ufs: qcom: Add support to disable UFS LPM Feature

[Rob Herring]

On Thu, Apr 17, 2025 at 06:16:45PM +0530, Nitin Rawat wrote:
> There are emulation FPGA platforms or other platforms where UFS low
> power mode is either unsupported or power efficiency is not a critical
> requirement.
> 
> Disable all low power mode UFS feature based on the "disable-lpm" device
> tree property parsed in platform driver.
> 
> Signed-off-by: Nitin Rawat <quic_nitirawa@quicinc.com>
> ---
>  drivers/ufs/host/ufs-qcom.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
> index 1b37449fbffc..1024edf36b68 100644
> --- a/drivers/ufs/host/ufs-qcom.c
> +++ b/drivers/ufs/host/ufs-qcom.c
> @@ -1014,13 +1014,14 @@ static void ufs_qcom_set_host_caps(struct ufs_hba *hba)
> 
>  static void ufs_qcom_set_caps(struct ufs_hba *hba)
>  {
> -	hba->caps |= UFSHCD_CAP_CLK_GATING | UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
> -	hba->caps |= UFSHCD_CAP_CLK_SCALING | UFSHCD_CAP_WB_WITH_CLK_SCALING;
> -	hba->caps |= UFSHCD_CAP_AUTO_BKOPS_SUSPEND;
> -	hba->caps |= UFSHCD_CAP_WB_EN;
> -	hba->caps |= UFSHCD_CAP_AGGR_POWER_COLLAPSE;
> -	hba->caps |= UFSHCD_CAP_RPM_AUTOSUSPEND;
> -
> +	if (!hba->disable_lpm) {
> +		hba->caps |= UFSHCD_CAP_CLK_GATING | UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
> +		hba->caps |= UFSHCD_CAP_CLK_SCALING | UFSHCD_CAP_WB_WITH_CLK_SCALING;
> +		hba->caps |= UFSHCD_CAP_AUTO_BKOPS_SUSPEND;
> +		hba->caps |= UFSHCD_CAP_WB_EN;
> +		hba->caps |= UFSHCD_CAP_AGGR_POWER_COLLAPSE;
> +		hba->caps |= UFSHCD_CAP_RPM_AUTOSUSPEND;
> +	}

Doesn't RuntimePM already have userspace controls? And that's a Linux 
feature that shouldn't really be controlled by DT. I think this property 
should still to things defined by the UFS spec.

Rob

Re: [PATCH V1 3/3] scsi: ufs: qcom: Add support to disable UFS LPM Feature

[Nitin Rawat]

On 4/22/2025 6:15 PM, Rob Herring wrote:
> On Thu, Apr 17, 2025 at 06:16:45PM +0530, Nitin Rawat wrote:
>> There are emulation FPGA platforms or other platforms where UFS low
>> power mode is either unsupported or power efficiency is not a critical
>> requirement.
>>
>> Disable all low power mode UFS feature based on the "disable-lpm" device
>> tree property parsed in platform driver.
>>
>> Signed-off-by: Nitin Rawat <quic_nitirawa@quicinc.com>
>> ---
>>   drivers/ufs/host/ufs-qcom.c | 15 ++++++++-------
>>   1 file changed, 8 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
>> index 1b37449fbffc..1024edf36b68 100644
>> --- a/drivers/ufs/host/ufs-qcom.c
>> +++ b/drivers/ufs/host/ufs-qcom.c
>> @@ -1014,13 +1014,14 @@ static void ufs_qcom_set_host_caps(struct ufs_hba *hba)
>>
>>   static void ufs_qcom_set_caps(struct ufs_hba *hba)
>>   {
>> -	hba->caps |= UFSHCD_CAP_CLK_GATING | UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
>> -	hba->caps |= UFSHCD_CAP_CLK_SCALING | UFSHCD_CAP_WB_WITH_CLK_SCALING;
>> -	hba->caps |= UFSHCD_CAP_AUTO_BKOPS_SUSPEND;
>> -	hba->caps |= UFSHCD_CAP_WB_EN;
>> -	hba->caps |= UFSHCD_CAP_AGGR_POWER_COLLAPSE;
>> -	hba->caps |= UFSHCD_CAP_RPM_AUTOSUSPEND;
>> -
>> +	if (!hba->disable_lpm) {
>> +		hba->caps |= UFSHCD_CAP_CLK_GATING | UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
>> +		hba->caps |= UFSHCD_CAP_CLK_SCALING | UFSHCD_CAP_WB_WITH_CLK_SCALING;
>> +		hba->caps |= UFSHCD_CAP_AUTO_BKOPS_SUSPEND;
>> +		hba->caps |= UFSHCD_CAP_WB_EN;
>> +		hba->caps |= UFSHCD_CAP_AGGR_POWER_COLLAPSE;
>> +		hba->caps |= UFSHCD_CAP_RPM_AUTOSUSPEND;
>> +	}
> 
> Doesn't RuntimePM already have userspace controls? And that's a Linux
> feature that shouldn't really be controlled by DT. I think this property
> should still to things defined by the UFS spec.

Hi Rob,
Yes userspace has runtime PM control but by the time UFS driver probes 
completes and userspace is up, there are chances runtime PM may get 
kicked in.

Regards,
Nitin

> 
> Rob

Re: [PATCH V1 3/3] scsi: ufs: qcom: Add support to disable UFS LPM Feature

[Peter Wang (王信友)]

On Thu, 2025-04-17 at 18:16 +0530, Nitin Rawat wrote:
> 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
> 
> 
> There are emulation FPGA platforms or other platforms where UFS low
> power mode is either unsupported or power efficiency is not a
> critical
> requirement.
> 
> Disable all low power mode UFS feature based on the "disable-lpm"
> device
> tree property parsed in platform driver.
> 
> Signed-off-by: Nitin Rawat <quic_nitirawa@quicinc.com>
> ---
>  drivers/ufs/host/ufs-qcom.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-
> qcom.c
> index 1b37449fbffc..1024edf36b68 100644
> --- a/drivers/ufs/host/ufs-qcom.c
> +++ b/drivers/ufs/host/ufs-qcom.c
> @@ -1014,13 +1014,14 @@ static void ufs_qcom_set_host_caps(struct
> ufs_hba *hba)
> 
>  static void ufs_qcom_set_caps(struct ufs_hba *hba)
>  {
> -       hba->caps |= UFSHCD_CAP_CLK_GATING |
> UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
> -       hba->caps |= UFSHCD_CAP_CLK_SCALING |
> UFSHCD_CAP_WB_WITH_CLK_SCALING;
> -       hba->caps |= UFSHCD_CAP_AUTO_BKOPS_SUSPEND;
> -       hba->caps |= UFSHCD_CAP_WB_EN;
> -       hba->caps |= UFSHCD_CAP_AGGR_POWER_COLLAPSE;
> -       hba->caps |= UFSHCD_CAP_RPM_AUTOSUSPEND;
> -
> +       if (!hba->disable_lpm) {
> +               hba->caps |= UFSHCD_CAP_CLK_GATING |
> UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
> +               hba->caps |= UFSHCD_CAP_CLK_SCALING |
> UFSHCD_CAP_WB_WITH_CLK_SCALING;
> +               hba->caps |= UFSHCD_CAP_AUTO_BKOPS_SUSPEND;
> +               hba->caps |= UFSHCD_CAP_WB_EN;
> 

Hi, Nitin,

If hba->disable_lpm is true, WB should enable?
Normally, you don't care about low power, so why wouldn't you enable
WB?

Thanks.
Peter



> +               hba->caps |= UFSHCD_CAP_AGGR_POWER_COLLAPSE;
> +               hba->caps |= UFSHCD_CAP_RPM_AUTOSUSPEND;
> +       }
>         ufs_qcom_set_host_caps(hba);
>  }
> 
> --
> 2.48.1
> 

Re: [PATCH V1 3/3] scsi: ufs: qcom: Add support to disable UFS LPM Feature

[Nitin Rawat]

On 4/23/2025 10:30 AM, Peter Wang (王信友) wrote:
> On Thu, 2025-04-17 at 18:16 +0530, Nitin Rawat wrote:
>>
>> External email : Please do not click links or open attachments until
>> you have verified the sender or the content.
>>
>>
>> There are emulation FPGA platforms or other platforms where UFS low
>> power mode is either unsupported or power efficiency is not a
>> critical
>> requirement.
>>
>> Disable all low power mode UFS feature based on the "disable-lpm"
>> device
>> tree property parsed in platform driver.
>>
>> Signed-off-by: Nitin Rawat <quic_nitirawa@quicinc.com>
>> ---
>>   drivers/ufs/host/ufs-qcom.c | 15 ++++++++-------
>>   1 file changed, 8 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-
>> qcom.c
>> index 1b37449fbffc..1024edf36b68 100644
>> --- a/drivers/ufs/host/ufs-qcom.c
>> +++ b/drivers/ufs/host/ufs-qcom.c
>> @@ -1014,13 +1014,14 @@ static void ufs_qcom_set_host_caps(struct
>> ufs_hba *hba)
>>
>>   static void ufs_qcom_set_caps(struct ufs_hba *hba)
>>   {
>> -       hba->caps |= UFSHCD_CAP_CLK_GATING |
>> UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
>> -       hba->caps |= UFSHCD_CAP_CLK_SCALING |
>> UFSHCD_CAP_WB_WITH_CLK_SCALING;
>> -       hba->caps |= UFSHCD_CAP_AUTO_BKOPS_SUSPEND;
>> -       hba->caps |= UFSHCD_CAP_WB_EN;
>> -       hba->caps |= UFSHCD_CAP_AGGR_POWER_COLLAPSE;
>> -       hba->caps |= UFSHCD_CAP_RPM_AUTOSUSPEND;
>> -
>> +       if (!hba->disable_lpm) {
>> +               hba->caps |= UFSHCD_CAP_CLK_GATING |
>> UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
>> +               hba->caps |= UFSHCD_CAP_CLK_SCALING |
>> UFSHCD_CAP_WB_WITH_CLK_SCALING;
>> +               hba->caps |= UFSHCD_CAP_AUTO_BKOPS_SUSPEND;
>> +               hba->caps |= UFSHCD_CAP_WB_EN;
>>
> 
> Hi, Nitin,
> 
> If hba->disable_lpm is true, WB should enable?
> Normally, you don't care about low power, so why wouldn't you enable
> WB?
> 
Hi Peter,

Thanks for review. Agree with you.
I will update this in next patchset.

Regards,
Nitin


> Thanks.
> Peter
> 
> 
> 
>> +               hba->caps |= UFSHCD_CAP_AGGR_POWER_COLLAPSE;
>> +               hba->caps |= UFSHCD_CAP_RPM_AUTOSUSPEND;
>> +       }
>>          ufs_qcom_set_host_caps(hba);
>>   }
>>
>> --
>> 2.48.1
>>
> 

Re: [PATCH V1 3/3] scsi: ufs: qcom: Add support to disable UFS LPM Feature

[Rob Herring]

On Wed, Apr 23, 2025 at 01:14:27AM +0530, Nitin Rawat wrote:
> 
> 
> On 4/22/2025 6:15 PM, Rob Herring wrote:
> > On Thu, Apr 17, 2025 at 06:16:45PM +0530, Nitin Rawat wrote:
> > > There are emulation FPGA platforms or other platforms where UFS low
> > > power mode is either unsupported or power efficiency is not a critical
> > > requirement.
> > > 
> > > Disable all low power mode UFS feature based on the "disable-lpm" device
> > > tree property parsed in platform driver.
> > > 
> > > Signed-off-by: Nitin Rawat <quic_nitirawa@quicinc.com>
> > > ---
> > >   drivers/ufs/host/ufs-qcom.c | 15 ++++++++-------
> > >   1 file changed, 8 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
> > > index 1b37449fbffc..1024edf36b68 100644
> > > --- a/drivers/ufs/host/ufs-qcom.c
> > > +++ b/drivers/ufs/host/ufs-qcom.c
> > > @@ -1014,13 +1014,14 @@ static void ufs_qcom_set_host_caps(struct ufs_hba *hba)
> > > 
> > >   static void ufs_qcom_set_caps(struct ufs_hba *hba)
> > >   {
> > > -	hba->caps |= UFSHCD_CAP_CLK_GATING | UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
> > > -	hba->caps |= UFSHCD_CAP_CLK_SCALING | UFSHCD_CAP_WB_WITH_CLK_SCALING;
> > > -	hba->caps |= UFSHCD_CAP_AUTO_BKOPS_SUSPEND;
> > > -	hba->caps |= UFSHCD_CAP_WB_EN;
> > > -	hba->caps |= UFSHCD_CAP_AGGR_POWER_COLLAPSE;
> > > -	hba->caps |= UFSHCD_CAP_RPM_AUTOSUSPEND;
> > > -
> > > +	if (!hba->disable_lpm) {
> > > +		hba->caps |= UFSHCD_CAP_CLK_GATING | UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
> > > +		hba->caps |= UFSHCD_CAP_CLK_SCALING | UFSHCD_CAP_WB_WITH_CLK_SCALING;
> > > +		hba->caps |= UFSHCD_CAP_AUTO_BKOPS_SUSPEND;
> > > +		hba->caps |= UFSHCD_CAP_WB_EN;
> > > +		hba->caps |= UFSHCD_CAP_AGGR_POWER_COLLAPSE;
> > > +		hba->caps |= UFSHCD_CAP_RPM_AUTOSUSPEND;
> > > +	}
> > 
> > Doesn't RuntimePM already have userspace controls? And that's a Linux
> > feature that shouldn't really be controlled by DT. I think this property
> > should still to things defined by the UFS spec.
> 
> Hi Rob,
> Yes userspace has runtime PM control but by the time UFS driver probes
> completes and userspace is up, there are chances runtime PM may get kicked
> in.

That sounds like a problem more than 1 device would have...

Rob

Re: [PATCH V1 3/3] scsi: ufs: qcom: Add support to disable UFS LPM Feature

[Nitin Rawat]

On 4/23/2025 7:26 PM, Rob Herring wrote:
> On Wed, Apr 23, 2025 at 01:14:27AM +0530, Nitin Rawat wrote:
>>
>>
>> On 4/22/2025 6:15 PM, Rob Herring wrote:
>>> On Thu, Apr 17, 2025 at 06:16:45PM +0530, Nitin Rawat wrote:
>>>> There are emulation FPGA platforms or other platforms where UFS low
>>>> power mode is either unsupported or power efficiency is not a critical
>>>> requirement.
>>>>
>>>> Disable all low power mode UFS feature based on the "disable-lpm" device
>>>> tree property parsed in platform driver.
>>>>
>>>> Signed-off-by: Nitin Rawat <quic_nitirawa@quicinc.com>
>>>> ---
>>>>    drivers/ufs/host/ufs-qcom.c | 15 ++++++++-------
>>>>    1 file changed, 8 insertions(+), 7 deletions(-)
>>>>
>>>> diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
>>>> index 1b37449fbffc..1024edf36b68 100644
>>>> --- a/drivers/ufs/host/ufs-qcom.c
>>>> +++ b/drivers/ufs/host/ufs-qcom.c
>>>> @@ -1014,13 +1014,14 @@ static void ufs_qcom_set_host_caps(struct ufs_hba *hba)
>>>>
>>>>    static void ufs_qcom_set_caps(struct ufs_hba *hba)
>>>>    {
>>>> -	hba->caps |= UFSHCD_CAP_CLK_GATING | UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
>>>> -	hba->caps |= UFSHCD_CAP_CLK_SCALING | UFSHCD_CAP_WB_WITH_CLK_SCALING;
>>>> -	hba->caps |= UFSHCD_CAP_AUTO_BKOPS_SUSPEND;
>>>> -	hba->caps |= UFSHCD_CAP_WB_EN;
>>>> -	hba->caps |= UFSHCD_CAP_AGGR_POWER_COLLAPSE;
>>>> -	hba->caps |= UFSHCD_CAP_RPM_AUTOSUSPEND;
>>>> -
>>>> +	if (!hba->disable_lpm) {
>>>> +		hba->caps |= UFSHCD_CAP_CLK_GATING | UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
>>>> +		hba->caps |= UFSHCD_CAP_CLK_SCALING | UFSHCD_CAP_WB_WITH_CLK_SCALING;
>>>> +		hba->caps |= UFSHCD_CAP_AUTO_BKOPS_SUSPEND;
>>>> +		hba->caps |= UFSHCD_CAP_WB_EN;
>>>> +		hba->caps |= UFSHCD_CAP_AGGR_POWER_COLLAPSE;
>>>> +		hba->caps |= UFSHCD_CAP_RPM_AUTOSUSPEND;
>>>> +	}
>>>
>>> Doesn't RuntimePM already have userspace controls? And that's a Linux
>>> feature that shouldn't really be controlled by DT. I think this property
>>> should still to things defined by the UFS spec.
>>
>> Hi Rob,
>> Yes userspace has runtime PM control but by the time UFS driver probes
>> completes and userspace is up, there are chances runtime PM may get kicked
>> in.
> 
> That sounds like a problem more than 1 device would have...

Yes, Rob, since there's a possibility that runtime suspend might be 
triggered for some devices before probe completes and userspace is up, 
IMO it's better to disable the runtime PM capability during 
initialization based on the device tree for specific FPGA platforms that 
don't support LPM.

What's your opinion on this?"

Regards,
Nitin



> 
> Rob