linux-kernel - Re: [PATCH] scsi: ufs: mediatek: avoid sched

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Message-ID: <b20bd855eb2ec7aab66dd0026fbda8e6625b30ef.camel@mediatek.com>
Date:   Wed, 20 Oct 2021 19:04:44 +0800
From:   Stanley Chu <stanley.chu@...iatek.com>
To:     Arnd Bergmann <arnd@...nel.org>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
CC:     Arnd Bergmann <arnd@...db.de>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        "Avri Altman" <avri.altman@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "Bean Huo" <beanhuo@...ron.com>,
        Peter Wang <peter.wang@...iatek.com>,
        "Bart Van Assche" <bvanassche@....org>,
        <linux-scsi@...r.kernel.org>, <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] scsi: ufs: mediatek: avoid sched_clock() misuse

Hi Arnd,

On Mon, 2021-10-18 at 15:20 +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> sched_clock() is not meant to be used in portable driver code,
> and assuming a particular clock frequency is not how this is
> meant to be used. It also causes a build failure because of
> a missing header inclusion:
> 
> drivers/scsi/ufs/ufs-mediatek.c:321:12: error: implicit declaration
> of function 'sched_clock' [-Werror,-Wimplicit-function-declaration]
>         timeout = sched_clock() + retry_ms * 1000000UL;
> 
> A better interface to use here ktime_get_mono_fast_ns(), which
> works mostly like ktime_get() but is safe to use inside of a
> suspend callback.
> 
> Fixes: 9561f58442e4 ("scsi: ufs: mediatek: Support vops pre suspend
> to disable auto-hibern8")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/scsi/ufs/ufs-mediatek.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufs-mediatek.c b/drivers/scsi/ufs/ufs-
> mediatek.c
> index d1696db70ce8..a47241ed0a57 100644
> --- a/drivers/scsi/ufs/ufs-mediatek.c
> +++ b/drivers/scsi/ufs/ufs-mediatek.c
> @@ -318,15 +318,15 @@ static void ufs_mtk_wait_idle_state(struct
> ufs_hba *hba,
>  	u32 val, sm;
>  	bool wait_idle;
>  
> -	timeout = sched_clock() + retry_ms * 1000000UL;
> -
> +	/* cannot use plain ktime_get() in suspend */
> +	timeout = ktime_get_mono_fast_ns() + retry_ms * 1000000UL;

Thanks for this fix.

Reviewed-by: Stanley Chu <stanley.chu@...iatek.com>

>  
>  	/* wait a specific time after check base */
>  	udelay(10);
>  	wait_idle = false;
>  
>  	do {
> -		time_checked = sched_clock();
> +		time_checked = ktime_get_mono_fast_ns();
>  		ufs_mtk_dbg_sel(hba);
>  		val = ufshcd_readl(hba, REG_UFS_PROBE);
>