linux-kernel - Re: [PATCH 1/2] iio: accel: adxl367: fix DEVID read after reset

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Date: Wed, 07 Feb 2024 10:11:06 +0100
From: Nuno Sá <noname.nuno@...il.com>
To: Cosmin Tanislav <demonsingur@...il.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>, Michael Hennerich
 <Michael.Hennerich@...log.com>, Cosmin Tanislav
 <cosmin.tanislav@...log.com>,  Jonathan Cameron <jic23@...nel.org>,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] iio: accel: adxl367: fix DEVID read after reset

On Wed, 2024-02-07 at 05:36 +0200, Cosmin Tanislav wrote:
> regmap_read_poll_timeout() will not sleep before reading,
> causing the first read to return -ENXIO on I2C, since the
> chip does not respond to it while it is being reset.
> 
> The datasheet specifies that a soft reset operation has a
> latency of 7.5ms.
> 
> Add a 15ms sleep between reset and reading the DEVID register,
> and switch to a simple regmap_read() call.
> 
> Signed-off-by: Cosmin Tanislav <demonsingur@...il.com>
> ---

This likely needs a Fixes: tag as well. With that,

Reviewed-by: Nuno Sa <nuno.sa@...log.com>

>  drivers/iio/accel/adxl367.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/accel/adxl367.c b/drivers/iio/accel/adxl367.c
> index 834ee6d63947..210228affb80 100644
> --- a/drivers/iio/accel/adxl367.c
> +++ b/drivers/iio/accel/adxl367.c
> @@ -1368,9 +1368,11 @@ static int adxl367_verify_devid(struct adxl367_state
> *st)
>  	unsigned int val;
>  	int ret;
>  
> -	ret = regmap_read_poll_timeout(st->regmap, ADXL367_REG_DEVID, val,
> -				       val == ADXL367_DEVID_AD, 1000, 10000);
> +	ret = regmap_read(st->regmap, ADXL367_REG_DEVID, &val);
>  	if (ret)
> +		return dev_err_probe(st->dev, ret, "Failed to read dev
> id\n");
> +
> +	if (val != ADXL367_DEVID_AD)
>  		return dev_err_probe(st->dev, -ENODEV,
>  				     "Invalid dev id 0x%02X, expected
> 0x%02X\n",
>  				     val, ADXL367_DEVID_AD);
> @@ -1449,6 +1451,8 @@ int adxl367_probe(struct device *dev, const struct
> adxl367_ops *ops,
>  	if (ret)
>  		return ret;
>  
> +	fsleep(15000);
> +
>  	ret = adxl367_verify_devid(st);
>  	if (ret)
>  		return ret;