linux-kernel - Re: [PATCH V4 3/4] scsi: ufs: core Enforce minimum pm level for sysfs configuration

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Message-ID: <p7icfbp2p6kpzcywfdgq6z33p3icrs3trtn2cmgf5lsgcxg34k@jtixkr6njmm5>
Date: Wed, 7 Jan 2026 22:21:11 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Shawn Lin <shawn.lin@...k-chips.com>
Cc: Ram Kumar Dwivedi <ram.dwivedi@....qualcomm.com>, 
	alim.akhtar@...sung.com, avri.altman@....com, bvanassche@....org, robh@...nel.org, 
	krzk+dt@...nel.org, conor+dt@...nel.org, James.Bottomley@...senpartnership.com, 
	martin.petersen@...cle.com, linux-arm-msm@...r.kernel.org, linux-scsi@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 3/4] scsi: ufs: core Enforce minimum pm level for
 sysfs configuration

On Tue, Jan 06, 2026 at 10:27:29PM +0800, Shawn Lin wrote:
> 在 2026/01/06 星期二 21:40, Ram Kumar Dwivedi 写道:
> > Some UFS platforms only support a limited subset of power levels.
> > Currently, the sysfs interface allows users to set any pm level
> > without validating the minimum supported value. If an unsupported
> > level is selected, suspend may fail.
> > 
> > Introduce an pm_lvl_min field in the ufs_hba structure and use it
> > to clamp the pm level requested via sysfs so that only supported
> > levels are accepted. Platforms that require a minimum pm level
> > can set this field during probe.
> > 
> > Signed-off-by: Ram Kumar Dwivedi <ram.dwivedi@....qualcomm.com>
> > ---
> >   drivers/ufs/core/ufs-sysfs.c | 2 +-
> >   include/ufs/ufshcd.h         | 1 +
> >   2 files changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/ufs/core/ufs-sysfs.c b/drivers/ufs/core/ufs-sysfs.c
> > index b33f8656edb5..02e5468ad49d 100644
> > --- a/drivers/ufs/core/ufs-sysfs.c
> > +++ b/drivers/ufs/core/ufs-sysfs.c
> > @@ -141,7 +141,7 @@ static inline ssize_t ufs_sysfs_pm_lvl_store(struct device *dev,
> >   	if (kstrtoul(buf, 0, &value))
> >   		return -EINVAL;
> > -	if (value >= UFS_PM_LVL_MAX)
> > +	if (value >= UFS_PM_LVL_MAX || value < hba->pm_lvl_min)
> 
> It makes sense that some platform support a limited subset of power
> levels. But each level is in increasing order of power savings, and you
> set it to UFS_PM_LVL_5. Don't you support UFS_PM_LVL_0 the full active
> mode?
> 

These are the suspend levels, not runtime levels. So yes, our platform doesn't
support full power mode when it is in suspend state.

- Mani

> >   		return -EINVAL;
> >   	if (ufs_pm_lvl_states[value].dev_state == UFS_DEEPSLEEP_PWR_MODE &&
> > diff --git a/include/ufs/ufshcd.h b/include/ufs/ufshcd.h
> > index 19154228780b..ac8697a7355b 100644
> > --- a/include/ufs/ufshcd.h
> > +++ b/include/ufs/ufshcd.h
> > @@ -972,6 +972,7 @@ struct ufs_hba {
> >   	enum ufs_pm_level rpm_lvl;
> >   	/* Desired UFS power management level during system PM */
> >   	enum ufs_pm_level spm_lvl;
> > +	enum ufs_pm_level pm_lvl_min;
> >   	int pm_op_in_progress;
> >   	/* Auto-Hibernate Idle Timer register value */
> 

-- 
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