[PATCH] iio: accel: bmc150: reset chip at init time

[PATCH] iio: accel: bmc150: reset chip at init time

[Olof Johansson]

In at least one known setup, the chip comes up in a state where reading
the chip ID returns garbage unless it's been reset, due to noise on the
wires during system boot.

All supported chips have the same reset method, and based on the
datasheets they all need 1.3 or 1.8ms to recover after reset. So, do
the conservative thing here and always reset the chip.

Signed-off-by: Olof Johansson <olof@lixom.net>
---
 drivers/iio/accel/bmc150-accel-core.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/iio/accel/bmc150-accel-core.c b/drivers/iio/accel/bmc150-accel-core.c
index bf17aae..59b380d 100644
--- a/drivers/iio/accel/bmc150-accel-core.c
+++ b/drivers/iio/accel/bmc150-accel-core.c
@@ -67,6 +67,9 @@
 #define BMC150_ACCEL_REG_PMU_BW		0x10
 #define BMC150_ACCEL_DEF_BW			125
 
+#define BMC150_ACCEL_REG_RESET			0x14
+#define BMC150_ACCEL_RESET_VAL			0xB6
+
 #define BMC150_ACCEL_REG_INT_MAP_0		0x19
 #define BMC150_ACCEL_INT_MAP_0_BIT_SLOPE	BIT(2)
 
@@ -1497,6 +1500,14 @@ static int bmc150_accel_chip_init(struct bmc150_accel_data *data)
 	int ret, i;
 	unsigned int val;
 
+	/*
+	 * Reset chip to get it in a known good state. A delay of 1.8ms after
+	 * reset is required according to the data sheets of supported chips.
+	 */
+	regmap_write(data->regmap, BMC150_ACCEL_REG_RESET,
+		     BMC150_ACCEL_RESET_VAL);
+	usleep_range(1800, 2500);
+
 	ret = regmap_read(data->regmap, BMC150_ACCEL_REG_CHIP_ID, &val);
 	if (ret < 0) {
 		dev_err(dev, "Error: Reading chip id\n");
-- 
2.8.0.rc3.29.gb552ff8

Re: [PATCH] iio: accel: bmc150: reset chip at init time

[Jonathan Cameron]

On 25/08/16 17:45, Olof Johansson wrote:
> In at least one known setup, the chip comes up in a state where reading
> the chip ID returns garbage unless it's been reset, due to noise on the
> wires during system boot.
> 
> All supported chips have the same reset method, and based on the
> datasheets they all need 1.3 or 1.8ms to recover after reset. So, do
> the conservative thing here and always reset the chip.
> 
> Signed-off-by: Olof Johansson <olof@lixom.net>
Looks good to me.

Srinivas, it's your driver. Can you take a quick look at this?

Thanks,

Jonathan
> ---
>  drivers/iio/accel/bmc150-accel-core.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/iio/accel/bmc150-accel-core.c b/drivers/iio/accel/bmc150-accel-core.c
> index bf17aae..59b380d 100644
> --- a/drivers/iio/accel/bmc150-accel-core.c
> +++ b/drivers/iio/accel/bmc150-accel-core.c
> @@ -67,6 +67,9 @@
>  #define BMC150_ACCEL_REG_PMU_BW		0x10
>  #define BMC150_ACCEL_DEF_BW			125
>  
> +#define BMC150_ACCEL_REG_RESET			0x14
> +#define BMC150_ACCEL_RESET_VAL			0xB6
> +
>  #define BMC150_ACCEL_REG_INT_MAP_0		0x19
>  #define BMC150_ACCEL_INT_MAP_0_BIT_SLOPE	BIT(2)
>  
> @@ -1497,6 +1500,14 @@ static int bmc150_accel_chip_init(struct bmc150_accel_data *data)
>  	int ret, i;
>  	unsigned int val;
>  
> +	/*
> +	 * Reset chip to get it in a known good state. A delay of 1.8ms after
> +	 * reset is required according to the data sheets of supported chips.
> +	 */
> +	regmap_write(data->regmap, BMC150_ACCEL_REG_RESET,
> +		     BMC150_ACCEL_RESET_VAL);
> +	usleep_range(1800, 2500);
> +
>  	ret = regmap_read(data->regmap, BMC150_ACCEL_REG_CHIP_ID, &val);
>  	if (ret < 0) {
>  		dev_err(dev, "Error: Reading chip id\n");
> 

Re: [PATCH] iio: accel: bmc150: reset chip at init time

[Srinivas Pandruvada]

On Mon, 2016-08-29 at 18:23 +0100, Jonathan Cameron wrote:
> On 25/08/16 17:45, Olof Johansson wrote:
> > 
> > In at least one known setup, the chip comes up in a state where
> > reading
> > the chip ID returns garbage unless it's been reset, due to noise on
> > the
> > wires during system boot.
> > 
> > All supported chips have the same reset method, and based on the
> > datasheets they all need 1.3 or 1.8ms to recover after reset. So,
> > do
> > the conservative thing here and always reset the chip.
> > 
> > Signed-off-by: Olof Johansson <olof@lixom.net>
Reviewed-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>

> Looks good to me.
> 
> Srinivas, it's your driver. Can you take a quick look at this?
> 
> Thanks,
> 
> Jonathan
> > 
> > ---
> >  drivers/iio/accel/bmc150-accel-core.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> > 
> > diff --git a/drivers/iio/accel/bmc150-accel-core.c
> > b/drivers/iio/accel/bmc150-accel-core.c
> > index bf17aae..59b380d 100644
> > --- a/drivers/iio/accel/bmc150-accel-core.c
> > +++ b/drivers/iio/accel/bmc150-accel-core.c
> > @@ -67,6 +67,9 @@
> >  #define BMC150_ACCEL_REG_PMU_BW		0x10
> >  #define BMC150_ACCEL_DEF_BW			125
> >  
> > +#define BMC150_ACCEL_REG_RESET			0x14
> > +#define BMC150_ACCEL_RESET_VAL			0xB6
> > +
> >  #define BMC150_ACCEL_REG_INT_MAP_0		0x19
> >  #define BMC150_ACCEL_INT_MAP_0_BIT_SLOPE	BIT(2)
> >  
> > @@ -1497,6 +1500,14 @@ static int bmc150_accel_chip_init(struct
> > bmc150_accel_data *data)
> >  	int ret, i;
> >  	unsigned int val;
> >  
> > +	/*
> > +	 * Reset chip to get it in a known good state. A delay of
> > 1.8ms after
> > +	 * reset is required according to the data sheets of
> > supported chips.
> > +	 */
> > +	regmap_write(data->regmap, BMC150_ACCEL_REG_RESET,
> > +		     BMC150_ACCEL_RESET_VAL);
> > +	usleep_range(1800, 2500);
> > +
> >  	ret = regmap_read(data->regmap, BMC150_ACCEL_REG_CHIP_ID,
> > &val);
> >  	if (ret < 0) {
> >  		dev_err(dev, "Error: Reading chip id\n");
> > 

Re: [PATCH] iio: accel: bmc150: reset chip at init time

[Jonathan Cameron]

On 30/08/16 20:45, Srinivas Pandruvada wrote:
> On Mon, 2016-08-29 at 18:23 +0100, Jonathan Cameron wrote:
>> On 25/08/16 17:45, Olof Johansson wrote:
>>>
>>> In at least one known setup, the chip comes up in a state where
>>> reading
>>> the chip ID returns garbage unless it's been reset, due to noise on
>>> the
>>> wires during system boot.
>>>
>>> All supported chips have the same reset method, and based on the
>>> datasheets they all need 1.3 or 1.8ms to recover after reset. So,
>>> do
>>> the conservative thing here and always reset the chip.
>>>
>>> Signed-off-by: Olof Johansson <olof@lixom.net>
> Reviewed-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Applied to the fixes-togreg branch of iio.git and marked for stable.

Thanks,

Jonathan
> 
>> Looks good to me.
>>
>> Srinivas, it's your driver. Can you take a quick look at this?
>>
>> Thanks,
>>
>> Jonathan
>>>
>>> ---
>>>  drivers/iio/accel/bmc150-accel-core.c | 11 +++++++++++
>>>  1 file changed, 11 insertions(+)
>>>
>>> diff --git a/drivers/iio/accel/bmc150-accel-core.c
>>> b/drivers/iio/accel/bmc150-accel-core.c
>>> index bf17aae..59b380d 100644
>>> --- a/drivers/iio/accel/bmc150-accel-core.c
>>> +++ b/drivers/iio/accel/bmc150-accel-core.c
>>> @@ -67,6 +67,9 @@
>>>  #define BMC150_ACCEL_REG_PMU_BW		0x10
>>>  #define BMC150_ACCEL_DEF_BW			125
>>>  
>>> +#define BMC150_ACCEL_REG_RESET			0x14
>>> +#define BMC150_ACCEL_RESET_VAL			0xB6
>>> +
>>>  #define BMC150_ACCEL_REG_INT_MAP_0		0x19
>>>  #define BMC150_ACCEL_INT_MAP_0_BIT_SLOPE	BIT(2)
>>>  
>>> @@ -1497,6 +1500,14 @@ static int bmc150_accel_chip_init(struct
>>> bmc150_accel_data *data)
>>>  	int ret, i;
>>>  	unsigned int val;
>>>  
>>> +	/*
>>> +	 * Reset chip to get it in a known good state. A delay of
>>> 1.8ms after
>>> +	 * reset is required according to the data sheets of
>>> supported chips.
>>> +	 */
>>> +	regmap_write(data->regmap, BMC150_ACCEL_REG_RESET,
>>> +		     BMC150_ACCEL_RESET_VAL);
>>> +	usleep_range(1800, 2500);
>>> +
>>>  	ret = regmap_read(data->regmap, BMC150_ACCEL_REG_CHIP_ID,
>>> &val);
>>>  	if (ret < 0) {
>>>  		dev_err(dev, "Error: Reading chip id\n");
>>>
> --
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