linux-kernel - RE: [PATCH] ufs: core: Initialize a variable mode for PA

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Message-ID: <065101dc3cc3$eda735c0$c8f5a140$@samsung.com>
Date: Tue, 14 Oct 2025 13:35:11 +0900
From: "Wonkon Kim" <wkon.kim@...sung.com>
To: "'Bart Van Assche'" <bvanassche@....org>,
	<James.Bottomley@...senPartnership.com>, <martin.petersen@...cle.com>,
	<peter.wang@...iatek.com>, <linux-scsi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] ufs: core: Initialize a variable mode for PA_PWRMODE

> On 10/13/25 1:20 AM, Wonkon Kim wrote:
> >> On 10/2/25 12:00 AM, Wonkon Kim wrote:
> >>>    static bool ufshcd_is_pwr_mode_restore_needed(struct ufs_hba *hba)
> >>>    {
> >>>    	struct ufs_pa_layer_attr *pwr_info = &hba->pwr_info;
> >>> -	u32 mode;
> >>> +	u32 mode = 0;
> >>>
> >>>    	ufshcd_dme_get(hba, UIC_ARG_MIB(PA_PWRMODE), &mode);
> >>
> >> Since there is more code that passes a pointer to an uninitialized
> >> variable to ufshcd_dme_get(), the untested patch below may be a
> >> better
> >> solution:
> >>
> >> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> >> index 127b691402f9..5226fbca29ec 100644
> >> --- a/drivers/ufs/core/ufshcd.c
> >> +++ b/drivers/ufs/core/ufshcd.c
> >> @@ -4277,8 +4277,8 @@ int ufshcd_dme_get_attr(struct ufs_hba *hba,
> >> u32 attr_sel,
> >>    			get, UIC_GET_ATTR_ID(attr_sel),
> >>    			UFS_UIC_COMMAND_RETRIES - retries);
> >>
> >> -	if (mib_val && !ret)
> >> -		*mib_val = uic_cmd.argument3;
> >> +	if (mib_val)
> >> +		*mib_val = ret == 0 ? uic_cmd.argument3 : 0;
> >>
> >>    	if (peer && (hba->quirks & UFSHCD_QUIRK_DME_PEER_ACCESS_AUTO_MODE)
> >>    	    && pwr_mode_change)
> >>
> >>
> >
> > There are some attributes to use 0 as valid value.
> > e.g. PA_MAXRXHSGEAR is set to 0 for NO_HS=0 If it has 0 for valid
> > value, most of value 0 are regarded as FALSE, unsupported or minimum.
> > And these cases seems to check ret for command success/fail in code.
> > However, is it ok to set 0 for ufshcd_send_uic_cmd() fail?
> >
> > If it can't, it needs to initialize mode.
> > Value 0 for PA_PWRMODE is invalid.
> 
> Hi Wonkon,
> 
> Modifying ufshcd_dme_get_attr() doesn't exclude checking the return value
> of ufshcd_dme_get_attr(). I propose to modify
> ufshcd_dme_get_attr() such that it always initializes *mib_val and also to
> check the ufshcd_dme_get_attr() return value wherever appropriate.
> 
> Thanks,
> 
> Bart.

Hi Bart,
I got it. I'll update it.


Thanks,
Wonkon Kim.