linux-kernel - Re: [PATCH v2 1/2] i2c: piix4: Use usleep

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Date:   Thu, 1 Mar 2018 12:04:04 +0100
From:   Jean Delvare <jdelvare@...e.de>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Wolfram Sang <wsa@...-dreams.de>, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] i2c: piix4: Use usleep_range()

On Mon, 26 Feb 2018 12:46:52 -0800, Guenter Roeck wrote:
> The piix4 i2c driver is extremely slow. Replacing msleep()
> with usleep_range() increases its speed substantially.
> Use sleep ranges similar to those used in the i2c-801 driver
> to keep things simple.
> 
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> ---
> v2: Changed timeout values for usleep_range()
>     2000/2000 -> 2000/2100
>     500/1000 -> 250/500
>     200/500 -> 250/500
> 
>  drivers/i2c/busses/i2c-piix4.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c
> index 462948e2c535..4c1f6aaec0fc 100644
> --- a/drivers/i2c/busses/i2c-piix4.c
> +++ b/drivers/i2c/busses/i2c-piix4.c
> @@ -462,13 +462,13 @@ static int piix4_transaction(struct i2c_adapter *piix4_adapter)
>  
>  	/* We will always wait for a fraction of a second! (See PIIX4 docs errata) */
>  	if (srvrworks_csb5_delay) /* Extra delay for SERVERWORKS_CSB5 */
> -		msleep(2);
> +		usleep_range(2000, 2100);
>  	else
> -		msleep(1);
> +		usleep_range(250, 500);
>  
>  	while ((++timeout < MAX_TIMEOUT) &&
>  	       ((temp = inb_p(SMBHSTSTS)) & 0x01))
> -		msleep(1);
> +		usleep_range(250, 500);
>  
>  	/* If the SMBus is still busy, we give up */
>  	if (timeout == MAX_TIMEOUT) {

Reviewed-by: Jean Delvare <jdelvare@...e.de>

-- 
Jean Delvare
SUSE L3 Support