linux-kernel - Re: [PATCH] scsi: ufs: core: Fix hba->last_dme_cmd

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Message-ID: <2bb22490-6209-4104-ae97-59d73fcb1d6d@acm.org>
Date: Mon, 29 Jul 2024 11:26:51 -0700
From: Bart Van Assche <bvanassche@....org>
To: Vamshi Gajjela <vamshigajjela@...gle.com>,
 Alim Akhtar <alim.akhtar@...sung.com>, Avri Altman <avri.altman@....com>
Cc: Yaniv Gardi <ygardi@...eaurora.org>, linux-scsi@...r.kernel.org,
 linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] scsi: ufs: core: Fix hba->last_dme_cmd_tstamp timestamp
 updating logic

On 7/24/24 6:51 AM, Vamshi Gajjela wrote:
> The ufshcd_add_delay_before_dme_cmd() always introduces a delay of
> MIN_DELAY_BEFORE_DME_CMDS_US between DME commands even when it's not
> required. The delay is added when the UFS host controller supplies the
> quirk UFSHCD_QUIRK_DELAY_BEFORE_DME_CMDS.
> 
> Fix the logic to update hba->last_dme_cmd_tstamp to ensure subsequent
> DME commands have the correct delay in the range of 0 to
> MIN_DELAY_BEFORE_DME_CMDS_US.
> 
> Update the timestamp at the end of the function to ensure it captures
> the latest time after any necessary delay has been applied.
> 
> Signed-off-by: Vamshi Gajjela <vamshigajjela@...gle.com>
> Fixes: cad2e03d8607 ("ufs: add support to allow non standard behaviours (quirks)")
> Cc: stable@...r.kernel.org
> ---
>   drivers/ufs/core/ufshcd.c | 11 ++++++++---
>   1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index dc757ba47522..406bda1585f6 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -4090,11 +4090,16 @@ static inline void ufshcd_add_delay_before_dme_cmd(struct ufs_hba *hba)
>   			min_sleep_time_us =
>   				MIN_DELAY_BEFORE_DME_CMDS_US - delta;
>   		else
> -			return; /* no more delay required */
> +			min_sleep_time_us = 0; /* no more delay required */
>   	}
>   
> -	/* allow sleep for extra 50us if needed */
> -	usleep_range(min_sleep_time_us, min_sleep_time_us + 50);
> +	if (min_sleep_time_us > 0) {
> +		/* allow sleep for extra 50us if needed */
> +		usleep_range(min_sleep_time_us, min_sleep_time_us + 50);
> +	}
> +
> +	/* update the last_dme_cmd_tstamp */
> +	hba->last_dme_cmd_tstamp = ktime_get();
>   }

Reviewed-by: Bart Van Assche <bvanassche@....org>