linux-kernel - Re: [PATCH 2/2] fsi/sbefifo: Fix reset timeout

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Date:   Fri, 24 Jul 2020 07:34:21 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Joel Stanley <joel@....id.au>, linux-fsi@...ts.ozlabs.org
Cc:     Joachim Fenkes <fenkes@...ibm.com>, linux-kernel@...r.kernel.org,
        Alistar Popple <alistair@...ple.id.au>
Subject: Re: [PATCH 2/2] fsi/sbefifo: Fix reset timeout

On 7/24/20 12:15 AM, Joel Stanley wrote:
> From: Joachim Fenkes <FENKES@...ibm.com>
> 
> On BMCs with lower timer resolution than 1ms, msleep(1) will take
> way longer than 1ms, so looping 10k times won't wait for 10s but
> significantly longer.
> 
> Fix this by using jiffies like the rest of the code.
> 
> Fixes: 9f4a8a2d7f9d ("fsi/sbefifo: Add driver for the SBE FIFO")
> Signed-off-by: Joachim Fenkes <fenkes@...ibm.com>
> Signed-off-by: Joel Stanley <joel@....id.au>
> ---
>  drivers/fsi/fsi-sbefifo.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/fsi/fsi-sbefifo.c b/drivers/fsi/fsi-sbefifo.c
> index 655b45c1f6ba..3ad9510ad4a4 100644
> --- a/drivers/fsi/fsi-sbefifo.c
> +++ b/drivers/fsi/fsi-sbefifo.c
> @@ -325,6 +325,7 @@ static int sbefifo_up_write(struct sbefifo *sbefifo, __be32 word)
>  static int sbefifo_request_reset(struct sbefifo *sbefifo)
>  {
>  	struct device *dev = &sbefifo->fsi_dev->dev;
> +	unsigned long end_time;
>  	u32 status, timeout;
>  	int rc;
>  
> @@ -341,7 +342,8 @@ static int sbefifo_request_reset(struct sbefifo *sbefifo)
>  	}
>  
>  	/* Wait for it to complete */
> -	for (timeout = 0; timeout < SBEFIFO_RESET_TIMEOUT; timeout++) {
> +	end_time = jiffies + msecs_to_jiffies(SBEFIFO_RESET_TIMEOUT);
> +	while (!time_after(jiffies, end_time)) {
>  		rc = sbefifo_regr(sbefifo, SBEFIFO_UP | SBEFIFO_STS, &status);
>  		if (rc) {
>  			dev_err(dev, "Failed to read UP fifo status during reset"
> @@ -355,7 +357,7 @@ static int sbefifo_request_reset(struct sbefifo *sbefifo)
>  			return 0;
>  		}
>  
> -		msleep(1);
> +		cond_resched();

A hot loop ? Are you sure ? usleep_range() might make more sense here.

Thanks,
Guenter

>  	}
>  	dev_err(dev, "FIFO reset timed out\n");
>  
>