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Date: Fri, 19 Jan 2024 14:33:32 -0600
From: Andrew Halaney <ahalaney@redhat.com>
To: Eric Chanudet <echanude@redhat.com>
Cc: Bjorn Andersson <andersson@kernel.org>, 
	Konrad Dybcio <konrad.dybcio@linaro.org>, Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>, 
	"James E.J. Bottomley" <jejb@linux.ibm.com>, "Martin K. Petersen" <martin.petersen@oracle.com>, 
	linux-arm-msm@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: Re: [PATCH] scsi: ufs: qcom: avoid re-init quirk when gears match
Message-ID: <otgj6524k6wiy27depeo7ckopmrr2v3xdnaoph4c5djjohnpmg@f7hyetygcyyr>
References: <20240119185537.3091366-11-echanude@redhat.com>
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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@redhat.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?
> 
> 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
> 
>     else if hw_ver == 4:
>         phy_gear = hs_tx_gear # (so afaict always UFS_HS_G4)
> 
>     else if hw_ver >= 5:
>         phy_gear = hs_tx_gear # (What ever the max is for this version)
> 
>         if dev_major:
>             # Clears the reinit quirk in ufs_qcom_set_phy_gear() if the
>             # device version is provided by bootloader / controller
>             # because we already found it out and can init directly
>             # to the ideal gear
>             quirks &= ~UFSHCD_QUIRK_REINIT_AFTER_MAX_GEAR_SWITCH
> 
>             if dev_major < 4:
>                 # Sets gear to UFS_HS_G4 to save power for UFS 3.1 and
>                 # older devices
>                 phy_gear = UFS_HS_G4
> 
> I guess what I'm saying is that I'm not totally seeing how this check
> is dependent on the controller version. To me, if we're in the ideal
> gear already and we know it, we should *not* reinit, no matter what the
> controller version is. That's assuming there's not some other reasoning
> for the quirk, but as far as I understand it the quirk exists because we
> have to start with *some* phy gear value so we can talk to the device,
> and once we discover what the device is capable of it makes sense to
> scale down (or up for older controllers) to the ideal gear setting for
> the attached device. Unfortunately to do the change we have to
> reprogram the phy which I guess is only acceptable if we reprogram
> everything (hence the reinit).
> 
> Does that make sense or do you think I'm missing something? I think say
> even for an older controller this makes sense, if its attached to a
> UFS_HS_G2 capable device there is no reason to reinit since we started
> up in the ideal configuration.

I guess what I'm saying is shouldn't the check be something like:

    if (dev_req_params->gear_tx == host->phy_gear) {
        // Skip reinit since we started up in the agreed upon gear
        hba->quirks &= ~UFSHCD_QUIRK_REINIT_AFTER_MAX_GEAR_SWITCH;
    }

Which is independent of the controller version?

> 
> Thanks,
> Andrew
> 
> > +			    host_params->hs_tx_gear == dev_req_params->gear_tx)
> > +				hba->quirks &= ~UFSHCD_QUIRK_REINIT_AFTER_MAX_GEAR_SWITCH;
> >  			host->phy_gear = dev_req_params->gear_tx;
> > +		}
> >  
> >  		/* enable the device ref clock before changing to HS mode */
> >  		if (!ufshcd_is_hs_mode(&hba->pwr_info) &&
> > -- 
> > 2.43.0
> > 
> >