* [PATCH] iio: accel: bmc150: reset chip at init time
@ 2016-08-25 16:45 Olof Johansson
2016-08-29 17:23 ` Jonathan Cameron
0 siblings, 1 reply; 4+ messages in thread
From: Olof Johansson @ 2016-08-25 16:45 UTC (permalink / raw)
To: jic23; +Cc: knaack.h, lars, pmeerw, mpa, irina.tirdea, linux-iio,
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
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] iio: accel: bmc150: reset chip at init time
2016-08-25 16:45 [PATCH] iio: accel: bmc150: reset chip at init time Olof Johansson
@ 2016-08-29 17:23 ` Jonathan Cameron
2016-08-30 19:45 ` Srinivas Pandruvada
0 siblings, 1 reply; 4+ messages in thread
From: Jonathan Cameron @ 2016-08-29 17:23 UTC (permalink / raw)
To: Olof Johansson
Cc: knaack.h, lars, pmeerw, mpa, irina.tirdea, linux-iio,
Srinivas Pandruvada
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");
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] iio: accel: bmc150: reset chip at init time
2016-08-29 17:23 ` Jonathan Cameron
@ 2016-08-30 19:45 ` Srinivas Pandruvada
2016-09-03 16:27 ` Jonathan Cameron
0 siblings, 1 reply; 4+ messages in thread
From: Srinivas Pandruvada @ 2016-08-30 19:45 UTC (permalink / raw)
To: Jonathan Cameron, Olof Johansson
Cc: knaack.h, lars, pmeerw, mpa, irina.tirdea, linux-iio
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");
> >
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] iio: accel: bmc150: reset chip at init time
2016-08-30 19:45 ` Srinivas Pandruvada
@ 2016-09-03 16:27 ` Jonathan Cameron
0 siblings, 0 replies; 4+ messages in thread
From: Jonathan Cameron @ 2016-09-03 16:27 UTC (permalink / raw)
To: Srinivas Pandruvada, Olof Johansson
Cc: knaack.h, lars, pmeerw, mpa, irina.tirdea, linux-iio
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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^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2016-09-03 16:28 UTC | newest]
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2016-08-25 16:45 [PATCH] iio: accel: bmc150: reset chip at init time Olof Johansson
2016-08-29 17:23 ` Jonathan Cameron
2016-08-30 19:45 ` Srinivas Pandruvada
2016-09-03 16:27 ` Jonathan Cameron
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