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

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Message-ID: <20240123143615.GD19029@thinkpad>
Date: Tue, 23 Jan 2024 20:06:15 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Eric Chanudet <echanude@...hat.com>
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: [PATCH] scsi: ufs: qcom: avoid re-init quirk when gears
 match

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:
> > > > On sa8775p-ride, probing the hba will go through the
> > > > UFSHCD_QUIRK_REINIT_AFTER_MAX_GEAR_SWITCH path although the power info
> > > > are same during the second init.
> > > > 
> > > > If the host is at least v4, ufs_qcom_get_hs_gear() picked the highest
> > > > supported gear when setting the host_params. After the negotiation, if
> > > > the host and device are on the same gear, it is the highest gear
> > > > supported between the two. Skip the re-init to save some time.
> > > > 
> > > > Signed-off-by: Eric Chanudet <echanude@...hat.com>
> > > > ---
> > > > 
> > > > "trace_event=ufs:ufshcd_init" reports the time spent where the re-init
> > > > quirk is performed. On sa8775p-ride:
> > > > Baseline:
> > > >   0.355879: ufshcd_init: 1d84000.ufs: took 103377 usecs, dev_state: UFS_ACTIVE_PWR_MODE, link_state: UIC_LINK_ACTIVE_STATE, err 0
> > > > With this patch:
> > > >   0.297676: ufshcd_init: 1d84000.ufs: took 43553 usecs, dev_state: UFS_ACTIVE_PWR_MODE, link_state: UIC_LINK_ACTIVE_STATE, err 0
> > > > 
> > > >  drivers/ufs/host/ufs-qcom.c | 6 +++++-
> > > >  1 file changed, 5 insertions(+), 1 deletion(-)
> > > > 
> > > > 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.

- Mani

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