linux-kernel - Re: [PATCH] iio: bmg160: reset chip when probing

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Date:   Sat, 25 Mar 2017 16:37:11 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Quentin Schulz <quentin.schulz@...e-electrons.com>,
        knaack.h@....de, lars@...afoo.de, pmeerw@...erw.net
Cc:     irina.tirdea@...el.com, gregor.boirie@...rot.com,
        amsfield22@...il.com, s.trumtrar@...gutronix.de,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        thomas.petazzoni@...e-electrons.com
Subject: Re: [PATCH] iio: bmg160: reset chip when probing

On 21/03/17 15:52, Quentin Schulz wrote:
> The gyroscope chip might need to be reset to be used.
> 
> Without the chip being reset, the driver stopped at the first
> regmap_read (to get the CHIP_ID) and failed to probe.
> 
> The datasheet of the gyroscope says that a minimum wait of 30ms after
> the reset has to be done.
> 
> This patch has been checked on a BMX055 and the datasheet of the BMG160
> and the BMI055 give the same reset register and bits.
> 
> Signed-off-by: Quentin Schulz <quentin.schulz@...e-electrons.com>
Applied to the fixes-togreg branch of iio.git and marked for stable.

Thanks,

Jonathan
> ---
>  drivers/iio/gyro/bmg160_core.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/iio/gyro/bmg160_core.c b/drivers/iio/gyro/bmg160_core.c
> index f7fcfa8..821919d 100644
> --- a/drivers/iio/gyro/bmg160_core.c
> +++ b/drivers/iio/gyro/bmg160_core.c
> @@ -27,6 +27,7 @@
>  #include <linux/iio/trigger_consumer.h>
>  #include <linux/iio/triggered_buffer.h>
>  #include <linux/regmap.h>
> +#include <linux/delay.h>
>  #include "bmg160.h"
>  
>  #define BMG160_IRQ_NAME		"bmg160_event"
> @@ -52,6 +53,9 @@
>  #define BMG160_DEF_BW			100
>  #define BMG160_REG_PMU_BW_RES		BIT(7)
>  
> +#define BMG160_GYRO_REG_RESET		0x14
> +#define BMG160_GYRO_RESET_VAL		0xb6
> +
>  #define BMG160_REG_INT_MAP_0		0x17
>  #define BMG160_INT_MAP_0_BIT_ANY	BIT(1)
>  
> @@ -236,6 +240,14 @@ static int bmg160_chip_init(struct bmg160_data *data)
>  	int ret;
>  	unsigned int val;
>  
> +	/*
> +	 * Reset chip to get it in a known good state. A delay of 30ms after
> +	 * reset is required according to the datasheet.
> +	 */
> +	regmap_write(data->regmap, BMG160_GYRO_REG_RESET,
> +		     BMG160_GYRO_RESET_VAL);
> +	usleep_range(30000, 30700);
> +
>  	ret = regmap_read(data->regmap, BMG160_REG_CHIP_ID, &val);
>  	if (ret < 0) {
>  		dev_err(dev, "Error reading reg_chip_id\n");
>