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

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Message-ID: <5a59c4c4ec0959223fe0e879f2dd9d91@codeaurora.org>
Date:   Tue, 20 Oct 2020 18:57:38 +0800
From:   Can Guo <cang@...eaurora.org>
To:     jaegeuk@...nel.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 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.

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;