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

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Message-ID: <1e397063-9cf2-69d3-84fe-53c5776f2c5b@fau.de>
Date:   Fri, 21 Jun 2019 15:01:38 +0200
From:   Lukas Schneider <lukas.s.schneider@....de>
To:     Pavel Machek <pavel@....cz>
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


Am 21.06.2019 um 13:04 schrieb Pavel Machek:
> 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

According to Doucmentation/timers/timers-howto.txt, usleep_range should 
be used for sleep times between 10us and 20ms, so it is the correct 
function for 50us.

Lukas

>> @@ -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);
>>