linux-kernel - Re: [PATCH v2] scsi: ufs: fix clkgating on/off correctly

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Message-ID: <20201020191716.GA1726050@google.com>
Date:   Tue, 20 Oct 2020 12:17:16 -0700
From:   jaegeuk@...nel.org
To:     Can Guo <cang@...eaurora.org>
Cc:     linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        kernel-team@...roid.com, Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>
Subject: Re: [PATCH v2] scsi: ufs: fix clkgating on/off correctly

On 10/20, Can Guo wrote:
> On 2020-10-17 05:18, jaegeuk@...nel.org wrote:
> > The below call stack prevents clk_gating at every IO completion.
> > We can remove the condition, ufshcd_any_tag_in_use(), since
> > clkgating_work
> > will check it again.
> > 
> > ufshcd_complete_requests(struct ufs_hba *hba)
> >   ufshcd_transfer_req_compl()
> >     __ufshcd_transfer_req_compl()
> >       __ufshcd_release(hba)
> >         if (ufshcd_any_tag_in_use() == 1)
> >            return;
> >   ufshcd_tmc_handler(hba);
> >     blk_mq_tagset_busy_iter();
> > 
> > In addition, we have to avoid gate_work, if it was disabled.
> > 
> > Cc: Alim Akhtar <alim.akhtar@...sung.com>
> > Cc: Avri Altman <avri.altman@....com>
> > Cc: Can Guo <cang@...eaurora.org>
> > Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> > ---
> > 
> > Change log from v1:
> >  - change the patch subject
> >  - fix clkgate.is_enable to work
> > 
> >  drivers/scsi/ufs/ufshcd.c | 5 +++--
> >  drivers/scsi/ufs/ufshcd.h | 5 +++++
> >  2 files changed, 8 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> > index a2db8182663d..75e8a76f20c7 100644
> > --- a/drivers/scsi/ufs/ufshcd.c
> > +++ b/drivers/scsi/ufs/ufshcd.c
> > @@ -1729,9 +1729,10 @@ static void __ufshcd_release(struct ufs_hba *hba)
> > 
> >  	if (hba->clk_gating.active_reqs || hba->clk_gating.is_suspended
> >  		|| hba->ufshcd_state != UFSHCD_STATE_OPERATIONAL
> > -		|| ufshcd_any_tag_in_use(hba) || hba->outstanding_tasks
> > +		|| hba->outstanding_tasks
> >  		|| hba->active_uic_cmd || hba->uic_async_done
> > -		|| ufshcd_eh_in_progress(hba))
> > +		|| ufshcd_eh_in_progress(hba)
> > +		|| ufshcd_is_clkgating_enabled(hba))
> 
> I guess you want it to be "!ufshcd_is_clkgating_enabled(hba)" - if
> clk gating is enabled, we should let gating happen but not bail, right?
> 
> That said, I don't think we need to check whether clk gating is enabled or
> not here, since ufshcd_clkgating_store() manipulates clk_gating->active_reqs
> in an atomic way. If someone disables clk gating ->
> clk_gating->active_reqs++,
> this check becomes TURE on the very first condition.

Yeah, I found the above and and was testing it locally. Anyway, it seems you're
right. Let me give it a try back again.

Thanks,

> 
> So the very fisrt patch looks better to me.
> 
> Thanks,
> 
> Can Guo.
> 
> >  		return;
> > 
> >  	hba->clk_gating.state = REQ_CLKS_OFF;
> > diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
> > index 8344d8cb3678..09e59cb86e69 100644
> > --- a/drivers/scsi/ufs/ufshcd.h
> > +++ b/drivers/scsi/ufs/ufshcd.h
> > @@ -814,6 +814,11 @@ static inline bool
> > ufshcd_is_auto_hibern8_supported(struct ufs_hba *hba)
> >  		!(hba->quirks & UFSHCD_QUIRK_BROKEN_AUTO_HIBERN8);
> >  }
> > 
> > +static inline bool ufshcd_is_clkgating_enabled(struct ufs_hba *hba)
> > +{
> > +	return hba->clk_gating.is_enabled;
> > +}
> > +
> >  static inline bool ufshcd_is_auto_hibern8_enabled(struct ufs_hba *hba)
> >  {
> >  	return FIELD_GET(UFSHCI_AHIBERN8_TIMER_MASK, hba->ahit) ? true :
> > false;