linux-kernel - Re: [PATCH] Input: silead: use msleep() for long delays

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Date:   Thu, 12 Jan 2017 18:46:54 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Nicholas Mc Guire <hofrat@...dl.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Henrik Rydberg <rydberg@...math.org>,
        Rob Herring <robh@...nel.org>,
        Daniel Jansen <djaniboe@...il.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Robert Dolca <robert.dolca@...el.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: silead: use msleep() for long delays

Hi,

On 01/12/2017 05:21 PM, Nicholas Mc Guire wrote:
> the delays here are in the 10 to 20ms range so msleep() will do - no
> need to burden the highres timer subsystem.
>
> Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
> ---
>
> Problem found by coccinelle script
>
> While msleep(10) has a worst case uncertainty of 10ms (on HZ=100 systems)
> this seems ok here as the delays are not called frequently (init and
> reset functions)

By the same logic, this is not much of a burden on the high-res timer
subsys though.

> and the uncertainty of 10ms fits the permitted range of
> the original usleep_ranges().

Either way this patch is fine with me.

Regards,

Hans



>
> Patch was compile tested with: x86_64_defconfig +
> CONFIG_TOUCHSCREEN_SILEAD=m
>
> Patch is against 4.10-rc3 (localversion-next is next-20170112)
>
>  drivers/input/touchscreen/silead.c | 17 ++++++++---------
>  1 file changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/input/touchscreen/silead.c b/drivers/input/touchscreen/silead.c
> index 404830a..3aa885c 100644
> --- a/drivers/input/touchscreen/silead.c
> +++ b/drivers/input/touchscreen/silead.c
> @@ -58,8 +58,7 @@
>  #define SILEAD_POINT_X_MSB_OFF	0x03
>  #define SILEAD_TOUCH_ID_MASK	0xF0
>
> -#define SILEAD_CMD_SLEEP_MIN	10000
> -#define SILEAD_CMD_SLEEP_MAX	20000
> +#define SILEAD_CMD_SLEEP_MIN	10	/* 10+ ms */
>  #define SILEAD_POWER_SLEEP	20
>  #define SILEAD_STARTUP_SLEEP	30
>
> @@ -190,25 +189,25 @@ static int silead_ts_init(struct i2c_client *client)
>  					  SILEAD_CMD_RESET);
>  	if (error)
>  		goto i2c_write_err;
> -	usleep_range(SILEAD_CMD_SLEEP_MIN, SILEAD_CMD_SLEEP_MAX);
> +	msleep(SILEAD_CMD_SLEEP_MIN);
>
>  	error = i2c_smbus_write_byte_data(client, SILEAD_REG_TOUCH_NR,
>  					data->max_fingers);
>  	if (error)
>  		goto i2c_write_err;
> -	usleep_range(SILEAD_CMD_SLEEP_MIN, SILEAD_CMD_SLEEP_MAX);
> +	msleep(SILEAD_CMD_SLEEP_MIN);
>
>  	error = i2c_smbus_write_byte_data(client, SILEAD_REG_CLOCK,
>  					  SILEAD_CLOCK);
>  	if (error)
>  		goto i2c_write_err;
> -	usleep_range(SILEAD_CMD_SLEEP_MIN, SILEAD_CMD_SLEEP_MAX);
> +	msleep(SILEAD_CMD_SLEEP_MIN);
>
>  	error = i2c_smbus_write_byte_data(client, SILEAD_REG_RESET,
>  					  SILEAD_CMD_START);
>  	if (error)
>  		goto i2c_write_err;
> -	usleep_range(SILEAD_CMD_SLEEP_MIN, SILEAD_CMD_SLEEP_MAX);
> +	msleep(SILEAD_CMD_SLEEP_MIN);
>
>  	return 0;
>
> @@ -225,19 +224,19 @@ static int silead_ts_reset(struct i2c_client *client)
>  					  SILEAD_CMD_RESET);
>  	if (error)
>  		goto i2c_write_err;
> -	usleep_range(SILEAD_CMD_SLEEP_MIN, SILEAD_CMD_SLEEP_MAX);
> +	msleep(SILEAD_CMD_SLEEP_MIN);
>
>  	error = i2c_smbus_write_byte_data(client, SILEAD_REG_CLOCK,
>  					  SILEAD_CLOCK);
>  	if (error)
>  		goto i2c_write_err;
> -	usleep_range(SILEAD_CMD_SLEEP_MIN, SILEAD_CMD_SLEEP_MAX);
> +	msleep(SILEAD_CMD_SLEEP_MIN);
>
>  	error = i2c_smbus_write_byte_data(client, SILEAD_REG_POWER,
>  					  SILEAD_CMD_START);
>  	if (error)
>  		goto i2c_write_err;
> -	usleep_range(SILEAD_CMD_SLEEP_MIN, SILEAD_CMD_SLEEP_MAX);
> +	msleep(SILEAD_CMD_SLEEP_MIN);
>
>  	return 0;
>
>