linux-kernel - Re: [PATCH 4/4] rts5208: Fix usleep range is preferred over udelay

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Date:   Fri, 21 Jun 2019 13:04:05 +0200
From:   Pavel Machek <pavel@....cz>
To:     Lukas Schneider <lukas.s.schneider@....de>
Cc:     kim.jamie.bradley@...il.com, pakki001@....edu,
        colin.king@...onical.com, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, Jannik Moritz <jannik.moritz@....de>,
        linux-kernel@...cs.fau.de
Subject: Re: [PATCH 4/4] rts5208: Fix usleep range is preferred over udelay

On Wed 2019-06-19 17:46:48, Lukas Schneider wrote:
> This patch fixes the issue reported by checkpatch:
> 
> CHECK: usleep_range is preferred over udelay;
> see Doucmentation/timers/timers-howto.txt
> 
> It's save to sleep here instead of using busy waiting,
> because we are not in an atomic context.

Is it good idea? How can the system really sleep for 50 usec?

      	   	     	     	    	   	     Pavel

> @@ -865,7 +865,7 @@ static int sd_change_phase(struct rtsx_chip *chip, u8 sample_point, u8 tune_dir)
>  						     PHASE_CHANGE);
>  			if (retval)
>  				return retval;
> -			udelay(50);
> +			usleep_range(50, 60);
>  			retval = rtsx_write_register(chip, SD_VP_CTL, 0xFF,
>  						     PHASE_CHANGE |
>  						     PHASE_NOT_RESET |
> @@ -877,14 +877,14 @@ static int sd_change_phase(struct rtsx_chip *chip, u8 sample_point, u8 tune_dir)
>  						     CHANGE_CLK, CHANGE_CLK);
>  			if (retval)
>  				return retval;
> -			udelay(50);
> +			usleep_range(50, 60);
>  			retval = rtsx_write_register(chip, SD_VP_CTL, 0xFF,
>  						     PHASE_NOT_RESET |
>  						     sample_point);
>  			if (retval)
>  				return retval;
>  		}
> -		udelay(100);
> +		usleep_range(100, 110);
>  
>  		rtsx_init_cmd(chip);
>  		rtsx_add_cmd(chip, WRITE_REG_CMD, SD_DCMPS_CTL, DCMPS_CHANGE,
> @@ -918,7 +918,7 @@ static int sd_change_phase(struct rtsx_chip *chip, u8 sample_point, u8 tune_dir)
>  				return retval;
>  		}
>  
> -		udelay(50);
> +		usleep_range(50, 60);
>  	}
>  
>  	retval = rtsx_write_register(chip, SD_CFG1, SD_ASYNC_FIFO_NOT_RST, 0);
> @@ -1416,7 +1416,7 @@ static int sd_wait_data_idle(struct rtsx_chip *chip)
>  			retval = STATUS_SUCCESS;
>  			break;
>  		}
> -		udelay(100);
> +		usleep_range(100, 110);
>  	}
>  	dev_dbg(rtsx_dev(chip), "SD_DATA_STATE: 0x%02x\n", val);
>  

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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