linux-kernel - Re: Re: Re: Re: [PATCH] scsi: ufs: qcom: avoid re-init quirk when gears match

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Date: Tue, 23 Jan 2024 10:18:22 -0500
From: Eric Chanudet <echanude@...hat.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: Andrew Halaney <ahalaney@...hat.com>, 
	Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	"James E.J. Bottomley" <jejb@...ux.ibm.com>, "Martin K. Petersen" <martin.petersen@...cle.com>, 
	linux-arm-msm@...r.kernel.org, linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Re: Re: Re: [PATCH] scsi: ufs: qcom: avoid re-init quirk when
 gears match

On Tue, Jan 23, 2024 at 08:06:15PM +0530, Manivannan Sadhasivam wrote:
> On Fri, Jan 19, 2024 at 04:33:10PM -0500, Eric Chanudet wrote:
> > On Fri, Jan 19, 2024 at 02:33:32PM -0600, Andrew Halaney wrote:
> > > On Fri, Jan 19, 2024 at 02:07:15PM -0600, Andrew Halaney wrote:
> > > > On Fri, Jan 19, 2024 at 01:55:47PM -0500, Eric Chanudet wrote:
> > > > > diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
> > > > > index 39eef470f8fa..f9f161340e78 100644
> > > > > --- a/drivers/ufs/host/ufs-qcom.c
> > > > > +++ b/drivers/ufs/host/ufs-qcom.c
> > > > > @@ -738,8 +738,12 @@ static int ufs_qcom_pwr_change_notify(struct ufs_hba *hba,
> > > > >  		 * the second init can program the optimal PHY settings. This allows one to start
> > > > >  		 * the first init with either the minimum or the maximum support gear.
> > > > >  		 */
> > > > > -		if (hba->ufshcd_state == UFSHCD_STATE_RESET)
> > > > > +		if (hba->ufshcd_state == UFSHCD_STATE_RESET) {
> > > > > +			if (host->hw_ver.major >= 0x4 &&
> > > > 
> > > > Is this check really necessary?
> > 
> > I *think* so.
> > 
> > For example, if hw_ver < 4, ufs_qcom_set_phy_gear() has a comment saying
> > "power up the PHY using minimum supported gear (UFS_HS_G2). Switching to
> > max gear will be performed during reinit if supported."
> > 
> > > > 
> > > > The initial phy_gear state is something like this (my phrasing of
> > > > ufs_qcom_set_phy_gear()):
> > > > 
> > > >     if hw_ver < 4:
> > > >         # Comments about powering up with minimum gear (with no
> > > >         # reasoning in the comment afaict), and mentions switching
> > > >         # to higher gear in reinit quirk. This is opposite of the later
> > > >         # versions which start at the max and scale down
> > > >         phy_gear = UFS_HS_G2
> > 
> > IIUC, the device would not be able to negotiate a gear higher than the
> > minimum set for the phy_gear on initialization.
> > 
> > ufshcd_init_host_params() and ufs_qcom_get_hs_gear() both set the
> > controller <v4 host_params to G3. So if the device is HS capable, the
> > re-init would set G3, instead of the G2 selected by
> > ufs_qcom_set_phy_gear().
> > 
> 
> REINIT quirk is applicable for controllers starting from v4 only, because legacy
> controllers don't need separate PHY init sequences. So you can get rid of that
> check.

My bad, I overlooked the check in ufs_qcom_advertise_quirks().
Thank you, I'll send a v2 soon.

> - Mani
> 
> -- 
> மணிவண்ணன் சதாசிவம்
> 

-- 
Eric Chanudet