linux-kernel - Re: [PATCH v1 2/2] scsi: ufs: disable interrupt during clock-gating

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Message-ID: <a36d111e-ef7f-9f9b-6f6a-692a9980103a@codeaurora.org>
Date:   Tue, 17 Dec 2019 15:25:27 -0800
From:   "Asutosh Das (asd)" <asutoshd@...eaurora.org>
To:     Stanley Chu <stanley.chu@...iatek.com>, linux-scsi@...r.kernel.org,
        martin.petersen@...cle.com, avri.altman@....com,
        alim.akhtar@...sung.com, pedrom.sousa@...opsys.com,
        jejb@...ux.ibm.com, matthias.bgg@...il.com
Cc:     linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        beanhuo@...ron.com, kuohong.wang@...iatek.com,
        peter.wang@...iatek.com, chun-hung.wu@...iatek.com,
        andy.teng@...iatek.com
Subject: Re: [PATCH v1 2/2] scsi: ufs: disable interrupt during clock-gating

On 12/7/2019 4:22 AM, Stanley Chu wrote:
> Similar to suspend, ufshcd interrupt can be disabled since
> there won't be any host controller transaction expected till
> clocks ungated.
> 
> Signed-off-by: Stanley Chu <stanley.chu@...iatek.com>
> ---
>   drivers/scsi/ufs/ufshcd.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index f80bd4e811cb..5de105e82c32 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -1490,6 +1490,8 @@ static void ufshcd_ungate_work(struct work_struct *work)
>   	spin_unlock_irqrestore(hba->host->host_lock, flags);
>   	ufshcd_setup_clocks(hba, true);
>   
> +	ufshcd_enable_irq(hba);
> +
>   	/* Exit from hibern8 */
>   	if (ufshcd_can_hibern8_during_gating(hba)) {
>   		/* Prevent gating in this path */
> @@ -1636,6 +1638,8 @@ static void ufshcd_gate_work(struct work_struct *work)
>   		ufshcd_set_link_hibern8(hba);
>   	}
>   
> +	ufshcd_disable_irq(hba);
> +
>   	if (!ufshcd_is_link_active(hba))
>   		ufshcd_setup_clocks(hba, false);
>   	else
> 

Hi,
Does this save significant power? I see that gate/ungate of clocks 
happen far too frequently than suspend/resume.

Have you considered how much latency this would add to the 
gating/ungating path?

-asd

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