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

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Date:   Sun, 11 Feb 2018 12:12:22 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Wolfram Sang <wsa@...-dreams.de>
Cc:     Jean Delvare <jdelvare@...e.com>,
        Zoltán Böszörményi <zboszor@...hu>,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [2/2] i2c: piix4: Use usleep_range()

On Sat, Dec 30, 2017 at 08:50:58AM -0800, Guenter Roeck wrote:
> The piix4 i2c driver is extremely slow. Replacing msleep()
> with usleep_range() increases its speed substantially.
> 
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>

Any comments or concerns ?

Thanks,
Guenter

> ---
>  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 78dd5951d6e7..52a8b1c5c110 100644
> --- a/drivers/i2c/busses/i2c-piix4.c
> +++ b/drivers/i2c/busses/i2c-piix4.c
> @@ -467,13 +467,13 @@ 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, 2000);
>  	else
> -		msleep(1);
> +		usleep_range(500, 1000);
>  
>  	while ((++timeout < MAX_TIMEOUT) &&
>  	       ((temp = inb_p(SMBHSTSTS)) & 0x01))
> -		msleep(1);
> +		usleep_range(200, 500);
>  
>  	/* If the SMBus is still busy, we give up */
>  	if (timeout == MAX_TIMEOUT) {