iio: adc: axp288: Drop bogus AXP288_ADC_TS_PIN_CTRL register modifications
diff mbox

Message ID 20161214135525.16477-1-hdegoede@redhat.com
State Not Applicable
Headers show

Commit Message

Hans de Goede Dec. 14, 2016, 1:55 p.m. UTC
For some reason the axp288_adc driver was modifying the
AXP288_ADC_TS_PIN_CTRL register, changing bits 0-1 depending on
whether the GP_ADC channel or another channel was written.

These bits control when a bias current is send to the TS_PIN, the
GP_ADC has its own pin and a separate bit in another register to
control the bias current.

Not only does changing when to enable the TS_PIN bias current
(always or only when sampling) when reading the GP_ADC make no sense
at all, the code is modifying these bits is writing the entire register,
assuming that all the other bits have their default value.

So if the firmware has configured a different bias-current for either
pin, then that change gets clobbered by the write, likewise if the
firmware has set bit 2 to indicate that the battery has no thermal sensor,
this will get clobbered by the write.

This commit fixes all this, by simply removing all writes to the
AXP288_ADC_TS_PIN_CTRL register, they are not needed to read the
GP_ADC pin, and can actually be harmful.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/iio/adc/axp288_adc.c | 32 +-------------------------------
 1 file changed, 1 insertion(+), 31 deletions(-)

Comments

Chen-Yu Tsai Dec. 14, 2016, 3 p.m. UTC | #1
On Wed, Dec 14, 2016 at 9:55 PM, Hans de Goede <hdegoede@redhat.com> wrote:
> For some reason the axp288_adc driver was modifying the
> AXP288_ADC_TS_PIN_CTRL register, changing bits 0-1 depending on
> whether the GP_ADC channel or another channel was written.
>
> These bits control when a bias current is send to the TS_PIN, the
> GP_ADC has its own pin and a separate bit in another register to
> control the bias current.
>
> Not only does changing when to enable the TS_PIN bias current
> (always or only when sampling) when reading the GP_ADC make no sense
> at all, the code is modifying these bits is writing the entire register,
> assuming that all the other bits have their default value.
>
> So if the firmware has configured a different bias-current for either
> pin, then that change gets clobbered by the write, likewise if the
> firmware has set bit 2 to indicate that the battery has no thermal sensor,
> this will get clobbered by the write.
>
> This commit fixes all this, by simply removing all writes to the
> AXP288_ADC_TS_PIN_CTRL register, they are not needed to read the
> GP_ADC pin, and can actually be harmful.
>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Acked-by: Chen-Yu Tsai <wens@csie.org>

Note that I do not have hardware to test this.
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Jonathan Cameron Dec. 30, 2016, 4:46 p.m. UTC | #2
On 14/12/16 13:55, Hans de Goede wrote:
> For some reason the axp288_adc driver was modifying the
> AXP288_ADC_TS_PIN_CTRL register, changing bits 0-1 depending on
> whether the GP_ADC channel or another channel was written.
> 
> These bits control when a bias current is send to the TS_PIN, the
> GP_ADC has its own pin and a separate bit in another register to
> control the bias current.
> 
> Not only does changing when to enable the TS_PIN bias current
> (always or only when sampling) when reading the GP_ADC make no sense
> at all, the code is modifying these bits is writing the entire register,
> assuming that all the other bits have their default value.
> 
> So if the firmware has configured a different bias-current for either
> pin, then that change gets clobbered by the write, likewise if the
> firmware has set bit 2 to indicate that the battery has no thermal sensor,
> this will get clobbered by the write.
> 
> This commit fixes all this, by simply removing all writes to the
> AXP288_ADC_TS_PIN_CTRL register, they are not needed to read the
> GP_ADC pin, and can actually be harmful.
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
I guess you probably have more up to date contact details than I do,
but seems worth trying to cc Jacob Pan on this to see if we can find
out what the original reasoning behind this was.  Seems a very odd
thing to do with no purpose!

If Jacob isn't contactable we'll fall back to guessing it was just
an oddity of driver evolution.

Jonathan
> ---
>  drivers/iio/adc/axp288_adc.c | 32 +-------------------------------
>  1 file changed, 1 insertion(+), 31 deletions(-)
> 
> diff --git a/drivers/iio/adc/axp288_adc.c b/drivers/iio/adc/axp288_adc.c
> index 7fd2494..64799ad 100644
> --- a/drivers/iio/adc/axp288_adc.c
> +++ b/drivers/iio/adc/axp288_adc.c
> @@ -28,8 +28,6 @@
>  #include <linux/iio/driver.h>
>  
>  #define AXP288_ADC_EN_MASK		0xF1
> -#define AXP288_ADC_TS_PIN_GPADC		0xF2
> -#define AXP288_ADC_TS_PIN_ON		0xF3
>  
>  enum axp288_adc_id {
>  	AXP288_ADC_TS,
> @@ -123,16 +121,6 @@ static int axp288_adc_read_channel(int *val, unsigned long address,
>  	return IIO_VAL_INT;
>  }
>  
> -static int axp288_adc_set_ts(struct regmap *regmap, unsigned int mode,
> -				unsigned long address)
> -{
> -	/* channels other than GPADC do not need to switch TS pin */
> -	if (address != AXP288_GP_ADC_H)
> -		return 0;
> -
> -	return regmap_write(regmap, AXP288_ADC_TS_PIN_CTRL, mode);
> -}
> -
>  static int axp288_adc_read_raw(struct iio_dev *indio_dev,
>  			struct iio_chan_spec const *chan,
>  			int *val, int *val2, long mask)
> @@ -143,16 +131,7 @@ static int axp288_adc_read_raw(struct iio_dev *indio_dev,
>  	mutex_lock(&indio_dev->mlock);
>  	switch (mask) {
>  	case IIO_CHAN_INFO_RAW:
> -		if (axp288_adc_set_ts(info->regmap, AXP288_ADC_TS_PIN_GPADC,
> -					chan->address)) {
> -			dev_err(&indio_dev->dev, "GPADC mode\n");
> -			ret = -EINVAL;
> -			break;
> -		}
>  		ret = axp288_adc_read_channel(val, chan->address, info->regmap);
> -		if (axp288_adc_set_ts(info->regmap, AXP288_ADC_TS_PIN_ON,
> -						chan->address))
> -			dev_err(&indio_dev->dev, "TS pin restore\n");
>  		break;
>  	default:
>  		ret = -EINVAL;
> @@ -162,15 +141,6 @@ static int axp288_adc_read_raw(struct iio_dev *indio_dev,
>  	return ret;
>  }
>  
> -static int axp288_adc_set_state(struct regmap *regmap)
> -{
> -	/* ADC should be always enabled for internal FG to function */
> -	if (regmap_write(regmap, AXP288_ADC_TS_PIN_CTRL, AXP288_ADC_TS_PIN_ON))
> -		return -EIO;
> -
> -	return regmap_write(regmap, AXP20X_ADC_EN1, AXP288_ADC_EN_MASK);
> -}
> -
>  static const struct iio_info axp288_adc_iio_info = {
>  	.read_raw = &axp288_adc_read_raw,
>  	.driver_module = THIS_MODULE,
> @@ -199,7 +169,7 @@ static int axp288_adc_probe(struct platform_device *pdev)
>  	 * Set ADC to enabled state at all time, including system suspend.
>  	 * otherwise internal fuel gauge functionality may be affected.
>  	 */
> -	ret = axp288_adc_set_state(axp20x->regmap);
> +	ret = regmap_write(info->regmap, AXP20X_ADC_EN1, AXP288_ADC_EN_MASK);
>  	if (ret) {
>  		dev_err(&pdev->dev, "unable to enable ADC device\n");
>  		return ret;
> 

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Jacob Pan Dec. 30, 2016, 6:15 p.m. UTC | #3
On Fri, 30 Dec 2016 16:46:03 +0000
Jonathan Cameron <jic23@kernel.org> wrote:

> On 14/12/16 13:55, Hans de Goede wrote:
> > For some reason the axp288_adc driver was modifying the
> > AXP288_ADC_TS_PIN_CTRL register, changing bits 0-1 depending on
> > whether the GP_ADC channel or another channel was written.
> > 
> > These bits control when a bias current is send to the TS_PIN, the
> > GP_ADC has its own pin and a separate bit in another register to
> > control the bias current.
> > 
It has been a while. Just looked at the datasheet, reg 84h is for ADC
and TS pin control. IIRC, we had to set the TS bits in order to make
ADC read to work. What is the other register?

> > Not only does changing when to enable the TS_PIN bias current
> > (always or only when sampling) when reading the GP_ADC make no sense
> > at all, the code is modifying these bits is writing the entire
> > register, assuming that all the other bits have their default value.
> > 
Agreed, it would be better to do read-modify-write and not to
touch the other bits.
> > So if the firmware has configured a different bias-current for
> > either pin, then that change gets clobbered by the write, likewise
> > if the firmware has set bit 2 to indicate that the battery has no
> > thermal sensor, this will get clobbered by the write.
> > 
> > This commit fixes all this, by simply removing all writes to the
> > AXP288_ADC_TS_PIN_CTRL register, they are not needed to read the
> > GP_ADC pin, and can actually be harmful.
> > 
> > Signed-off-by: Hans de Goede <hdegoede@redhat.com>  
> I guess you probably have more up to date contact details than I do,
> but seems worth trying to cc Jacob Pan on this to see if we can find
> out what the original reasoning behind this was.  Seems a very odd
> thing to do with no purpose!
> 
> If Jacob isn't contactable we'll fall back to guessing it was just
> an oddity of driver evolution.
> 
> Jonathan
> > ---
> >  drivers/iio/adc/axp288_adc.c | 32 +-------------------------------
> >  1 file changed, 1 insertion(+), 31 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/axp288_adc.c
> > b/drivers/iio/adc/axp288_adc.c index 7fd2494..64799ad 100644
> > --- a/drivers/iio/adc/axp288_adc.c
> > +++ b/drivers/iio/adc/axp288_adc.c
> > @@ -28,8 +28,6 @@
> >  #include <linux/iio/driver.h>
> >  
> >  #define AXP288_ADC_EN_MASK		0xF1
> > -#define AXP288_ADC_TS_PIN_GPADC		0xF2
> > -#define AXP288_ADC_TS_PIN_ON		0xF3
> >  
> >  enum axp288_adc_id {
> >  	AXP288_ADC_TS,
> > @@ -123,16 +121,6 @@ static int axp288_adc_read_channel(int *val,
> > unsigned long address, return IIO_VAL_INT;
> >  }
> >  
> > -static int axp288_adc_set_ts(struct regmap *regmap, unsigned int
> > mode,
> > -				unsigned long address)
> > -{
> > -	/* channels other than GPADC do not need to switch TS pin
> > */
> > -	if (address != AXP288_GP_ADC_H)
> > -		return 0;
> > -
> > -	return regmap_write(regmap, AXP288_ADC_TS_PIN_CTRL, mode);
> > -}
> > -
> >  static int axp288_adc_read_raw(struct iio_dev *indio_dev,
> >  			struct iio_chan_spec const *chan,
> >  			int *val, int *val2, long mask)
> > @@ -143,16 +131,7 @@ static int axp288_adc_read_raw(struct iio_dev
> > *indio_dev, mutex_lock(&indio_dev->mlock);
> >  	switch (mask) {
> >  	case IIO_CHAN_INFO_RAW:
> > -		if (axp288_adc_set_ts(info->regmap,
> > AXP288_ADC_TS_PIN_GPADC,
> > -					chan->address)) {
> > -			dev_err(&indio_dev->dev, "GPADC mode\n");
> > -			ret = -EINVAL;
> > -			break;
> > -		}
> >  		ret = axp288_adc_read_channel(val, chan->address,
> > info->regmap);
> > -		if (axp288_adc_set_ts(info->regmap,
> > AXP288_ADC_TS_PIN_ON,
> > -						chan->address))
> > -			dev_err(&indio_dev->dev, "TS pin
> > restore\n"); break;
> >  	default:
> >  		ret = -EINVAL;
> > @@ -162,15 +141,6 @@ static int axp288_adc_read_raw(struct iio_dev
> > *indio_dev, return ret;
> >  }
> >  
> > -static int axp288_adc_set_state(struct regmap *regmap)
> > -{
> > -	/* ADC should be always enabled for internal FG to
> > function */
> > -	if (regmap_write(regmap, AXP288_ADC_TS_PIN_CTRL,
> > AXP288_ADC_TS_PIN_ON))
> > -		return -EIO;
> > -
> > -	return regmap_write(regmap, AXP20X_ADC_EN1,
> > AXP288_ADC_EN_MASK); -}
> > -
> >  static const struct iio_info axp288_adc_iio_info = {
> >  	.read_raw = &axp288_adc_read_raw,
> >  	.driver_module = THIS_MODULE,
> > @@ -199,7 +169,7 @@ static int axp288_adc_probe(struct
> > platform_device *pdev)
> >  	 * Set ADC to enabled state at all time, including system
> > suspend.
> >  	 * otherwise internal fuel gauge functionality may be
> > affected. */
> > -	ret = axp288_adc_set_state(axp20x->regmap);
> > +	ret = regmap_write(info->regmap, AXP20X_ADC_EN1,
> > AXP288_ADC_EN_MASK); if (ret) {
> >  		dev_err(&pdev->dev, "unable to enable ADC
> > device\n"); return ret;
> >   
> 

[Jacob Pan]
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Hans de Goede Jan. 1, 2017, 11:19 a.m. UTC | #4
Hi,

On 30-12-16 19:15, Jacob Pan wrote:
> On Fri, 30 Dec 2016 16:46:03 +0000
> Jonathan Cameron <jic23@kernel.org> wrote:
>
>> On 14/12/16 13:55, Hans de Goede wrote:
>>> For some reason the axp288_adc driver was modifying the
>>> AXP288_ADC_TS_PIN_CTRL register, changing bits 0-1 depending on
>>> whether the GP_ADC channel or another channel was written.
>>>
>>> These bits control when a bias current is send to the TS_PIN, the
>>> GP_ADC has its own pin and a separate bit in another register to
>>> control the bias current.
>>>
> It has been a while. Just looked at the datasheet, reg 84h is for ADC
> and TS pin control. IIRC, we had to set the TS bits in order to make
> ADC read to work.

The bits the code I'm removing are manipulating are bits 0 & 1 of
reg 84h which are:

1-0 Current source from TS pin on/off enable bit [1:0]

00: off
01: on when charging battery, off when not charging
10: on in ADC phase and off when out of the ADC phase, for power saving
11: always on

And they are being toggled between 10 and 11, so in both
cases the current source is enabled when reading the adc
value. Specifically the code this patch removes are setting
these bits to 10 before reading and back to 11 after reading,
which makes no sense.

And to make things even funkier, this manipulation is only
done when reading the GP_ADC, which is the ADC function of
GPIO0, whereas these bits control the bias current source
for the TS pin, which is a completely different pin.

So all in all this entire bit of code seems to be big NOP.

> What is the other register?

The register to actually enable / disable the bias current
source for GPIO0 / the GPADC pin is register 85h, where setting
bit 2 enables the GPIO0 output current.

Regards,

Hans



>>> Not only does changing when to enable the TS_PIN bias current
>>> (always or only when sampling) when reading the GP_ADC make no sense
>>> at all, the code is modifying these bits is writing the entire
>>> register, assuming that all the other bits have their default value.
>>>
> Agreed, it would be better to do read-modify-write and not to
> touch the other bits.
>>> So if the firmware has configured a different bias-current for
>>> either pin, then that change gets clobbered by the write, likewise
>>> if the firmware has set bit 2 to indicate that the battery has no
>>> thermal sensor, this will get clobbered by the write.
>>>
>>> This commit fixes all this, by simply removing all writes to the
>>> AXP288_ADC_TS_PIN_CTRL register, they are not needed to read the
>>> GP_ADC pin, and can actually be harmful.
>>>
>>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> I guess you probably have more up to date contact details than I do,
>> but seems worth trying to cc Jacob Pan on this to see if we can find
>> out what the original reasoning behind this was.  Seems a very odd
>> thing to do with no purpose!
>>
>> If Jacob isn't contactable we'll fall back to guessing it was just
>> an oddity of driver evolution.
>>
>> Jonathan
>>> ---
>>>  drivers/iio/adc/axp288_adc.c | 32 +-------------------------------
>>>  1 file changed, 1 insertion(+), 31 deletions(-)
>>>
>>> diff --git a/drivers/iio/adc/axp288_adc.c
>>> b/drivers/iio/adc/axp288_adc.c index 7fd2494..64799ad 100644
>>> --- a/drivers/iio/adc/axp288_adc.c
>>> +++ b/drivers/iio/adc/axp288_adc.c
>>> @@ -28,8 +28,6 @@
>>>  #include <linux/iio/driver.h>
>>>
>>>  #define AXP288_ADC_EN_MASK		0xF1
>>> -#define AXP288_ADC_TS_PIN_GPADC		0xF2
>>> -#define AXP288_ADC_TS_PIN_ON		0xF3
>>>
>>>  enum axp288_adc_id {
>>>  	AXP288_ADC_TS,
>>> @@ -123,16 +121,6 @@ static int axp288_adc_read_channel(int *val,
>>> unsigned long address, return IIO_VAL_INT;
>>>  }
>>>
>>> -static int axp288_adc_set_ts(struct regmap *regmap, unsigned int
>>> mode,
>>> -				unsigned long address)
>>> -{
>>> -	/* channels other than GPADC do not need to switch TS pin
>>> */
>>> -	if (address != AXP288_GP_ADC_H)
>>> -		return 0;
>>> -
>>> -	return regmap_write(regmap, AXP288_ADC_TS_PIN_CTRL, mode);
>>> -}
>>> -
>>>  static int axp288_adc_read_raw(struct iio_dev *indio_dev,
>>>  			struct iio_chan_spec const *chan,
>>>  			int *val, int *val2, long mask)
>>> @@ -143,16 +131,7 @@ static int axp288_adc_read_raw(struct iio_dev
>>> *indio_dev, mutex_lock(&indio_dev->mlock);
>>>  	switch (mask) {
>>>  	case IIO_CHAN_INFO_RAW:
>>> -		if (axp288_adc_set_ts(info->regmap,
>>> AXP288_ADC_TS_PIN_GPADC,
>>> -					chan->address)) {
>>> -			dev_err(&indio_dev->dev, "GPADC mode\n");
>>> -			ret = -EINVAL;
>>> -			break;
>>> -		}
>>>  		ret = axp288_adc_read_channel(val, chan->address,
>>> info->regmap);
>>> -		if (axp288_adc_set_ts(info->regmap,
>>> AXP288_ADC_TS_PIN_ON,
>>> -						chan->address))
>>> -			dev_err(&indio_dev->dev, "TS pin
>>> restore\n"); break;
>>>  	default:
>>>  		ret = -EINVAL;
>>> @@ -162,15 +141,6 @@ static int axp288_adc_read_raw(struct iio_dev
>>> *indio_dev, return ret;
>>>  }
>>>
>>> -static int axp288_adc_set_state(struct regmap *regmap)
>>> -{
>>> -	/* ADC should be always enabled for internal FG to
>>> function */
>>> -	if (regmap_write(regmap, AXP288_ADC_TS_PIN_CTRL,
>>> AXP288_ADC_TS_PIN_ON))
>>> -		return -EIO;
>>> -
>>> -	return regmap_write(regmap, AXP20X_ADC_EN1,
>>> AXP288_ADC_EN_MASK); -}
>>> -
>>>  static const struct iio_info axp288_adc_iio_info = {
>>>  	.read_raw = &axp288_adc_read_raw,
>>>  	.driver_module = THIS_MODULE,
>>> @@ -199,7 +169,7 @@ static int axp288_adc_probe(struct
>>> platform_device *pdev)
>>>  	 * Set ADC to enabled state at all time, including system
>>> suspend.
>>>  	 * otherwise internal fuel gauge functionality may be
>>> affected. */
>>> -	ret = axp288_adc_set_state(axp20x->regmap);
>>> +	ret = regmap_write(info->regmap, AXP20X_ADC_EN1,
>>> AXP288_ADC_EN_MASK); if (ret) {
>>>  		dev_err(&pdev->dev, "unable to enable ADC
>>> device\n"); return ret;
>>>
>>
>
> [Jacob Pan]
>
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Jacob Pan Jan. 3, 2017, 6:23 p.m. UTC | #5
On Sun, 1 Jan 2017 12:19:40 +0100
Hans de Goede <hdegoede@redhat.com> wrote:

> Hi,
> 
> On 30-12-16 19:15, Jacob Pan wrote:
> > On Fri, 30 Dec 2016 16:46:03 +0000
> > Jonathan Cameron <jic23@kernel.org> wrote:
> >  
> >> On 14/12/16 13:55, Hans de Goede wrote:  
> >>> For some reason the axp288_adc driver was modifying the
> >>> AXP288_ADC_TS_PIN_CTRL register, changing bits 0-1 depending on
> >>> whether the GP_ADC channel or another channel was written.
> >>>
> >>> These bits control when a bias current is send to the TS_PIN, the
> >>> GP_ADC has its own pin and a separate bit in another register to
> >>> control the bias current.
> >>>  
> > It has been a while. Just looked at the datasheet, reg 84h is for
> > ADC and TS pin control. IIRC, we had to set the TS bits in order to
> > make ADC read to work.  
> 
> The bits the code I'm removing are manipulating are bits 0 & 1 of
> reg 84h which are:
> 
> 1-0 Current source from TS pin on/off enable bit [1:0]
> 
> 00: off
> 01: on when charging battery, off when not charging
> 10: on in ADC phase and off when out of the ADC phase, for power
> saving 11: always on
> 
> And they are being toggled between 10 and 11, so in both
> cases the current source is enabled when reading the adc
> value. Specifically the code this patch removes are setting
> these bits to 10 before reading and back to 11 after reading,
> which makes no sense.
> 
> And to make things even funkier, this manipulation is only
> done when reading the GP_ADC, which is the ADC function of
> GPIO0, whereas these bits control the bias current source
> for the TS pin, which is a completely different pin.
> 
> So all in all this entire bit of code seems to be big NOP.
> 
It could have been a quirk we had to do on our platforms, I just
cannot recall the details. Are you testing this on x86 platforms?

> > What is the other register?  
> 
> The register to actually enable / disable the bias current
> source for GPIO0 / the GPADC pin is register 85h, where setting
> bit 2 enables the GPIO0 output current.
> 
> Regards,
> 
> Hans
> 
> 
> 
> >>> Not only does changing when to enable the TS_PIN bias current
> >>> (always or only when sampling) when reading the GP_ADC make no
> >>> sense at all, the code is modifying these bits is writing the
> >>> entire register, assuming that all the other bits have their
> >>> default value. 
> > Agreed, it would be better to do read-modify-write and not to
> > touch the other bits.  
> >>> So if the firmware has configured a different bias-current for
> >>> either pin, then that change gets clobbered by the write, likewise
> >>> if the firmware has set bit 2 to indicate that the battery has no
> >>> thermal sensor, this will get clobbered by the write.
> >>>
> >>> This commit fixes all this, by simply removing all writes to the
> >>> AXP288_ADC_TS_PIN_CTRL register, they are not needed to read the
> >>> GP_ADC pin, and can actually be harmful.
> >>>
> >>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>  
> >> I guess you probably have more up to date contact details than I
> >> do, but seems worth trying to cc Jacob Pan on this to see if we
> >> can find out what the original reasoning behind this was.  Seems a
> >> very odd thing to do with no purpose!
> >>
> >> If Jacob isn't contactable we'll fall back to guessing it was just
> >> an oddity of driver evolution.
> >>
> >> Jonathan  
> >>> ---
> >>>  drivers/iio/adc/axp288_adc.c | 32
> >>> +------------------------------- 1 file changed, 1 insertion(+),
> >>> 31 deletions(-)
> >>>
> >>> diff --git a/drivers/iio/adc/axp288_adc.c
> >>> b/drivers/iio/adc/axp288_adc.c index 7fd2494..64799ad 100644
> >>> --- a/drivers/iio/adc/axp288_adc.c
> >>> +++ b/drivers/iio/adc/axp288_adc.c
> >>> @@ -28,8 +28,6 @@
> >>>  #include <linux/iio/driver.h>
> >>>
> >>>  #define AXP288_ADC_EN_MASK		0xF1
> >>> -#define AXP288_ADC_TS_PIN_GPADC		0xF2
> >>> -#define AXP288_ADC_TS_PIN_ON		0xF3
> >>>
> >>>  enum axp288_adc_id {
> >>>  	AXP288_ADC_TS,
> >>> @@ -123,16 +121,6 @@ static int axp288_adc_read_channel(int *val,
> >>> unsigned long address, return IIO_VAL_INT;
> >>>  }
> >>>
> >>> -static int axp288_adc_set_ts(struct regmap *regmap, unsigned int
> >>> mode,
> >>> -				unsigned long address)
> >>> -{
> >>> -	/* channels other than GPADC do not need to switch TS pin
> >>> */
> >>> -	if (address != AXP288_GP_ADC_H)
> >>> -		return 0;
> >>> -
> >>> -	return regmap_write(regmap, AXP288_ADC_TS_PIN_CTRL,
> >>> mode); -}
> >>> -
> >>>  static int axp288_adc_read_raw(struct iio_dev *indio_dev,
> >>>  			struct iio_chan_spec const *chan,
> >>>  			int *val, int *val2, long mask)
> >>> @@ -143,16 +131,7 @@ static int axp288_adc_read_raw(struct iio_dev
> >>> *indio_dev, mutex_lock(&indio_dev->mlock);
> >>>  	switch (mask) {
> >>>  	case IIO_CHAN_INFO_RAW:
> >>> -		if (axp288_adc_set_ts(info->regmap,
> >>> AXP288_ADC_TS_PIN_GPADC,
> >>> -					chan->address)) {
> >>> -			dev_err(&indio_dev->dev, "GPADC mode\n");
> >>> -			ret = -EINVAL;
> >>> -			break;
> >>> -		}
> >>>  		ret = axp288_adc_read_channel(val, chan->address,
> >>> info->regmap);
> >>> -		if (axp288_adc_set_ts(info->regmap,
> >>> AXP288_ADC_TS_PIN_ON,
> >>> -						chan->address))
> >>> -			dev_err(&indio_dev->dev, "TS pin
> >>> restore\n"); break;
> >>>  	default:
> >>>  		ret = -EINVAL;
> >>> @@ -162,15 +141,6 @@ static int axp288_adc_read_raw(struct iio_dev
> >>> *indio_dev, return ret;
> >>>  }
> >>>
> >>> -static int axp288_adc_set_state(struct regmap *regmap)
> >>> -{
> >>> -	/* ADC should be always enabled for internal FG to
> >>> function */
> >>> -	if (regmap_write(regmap, AXP288_ADC_TS_PIN_CTRL,
> >>> AXP288_ADC_TS_PIN_ON))
> >>> -		return -EIO;
> >>> -
> >>> -	return regmap_write(regmap, AXP20X_ADC_EN1,
> >>> AXP288_ADC_EN_MASK); -}
> >>> -
> >>>  static const struct iio_info axp288_adc_iio_info = {
> >>>  	.read_raw = &axp288_adc_read_raw,
> >>>  	.driver_module = THIS_MODULE,
> >>> @@ -199,7 +169,7 @@ static int axp288_adc_probe(struct
> >>> platform_device *pdev)
> >>>  	 * Set ADC to enabled state at all time, including system
> >>> suspend.
> >>>  	 * otherwise internal fuel gauge functionality may be
> >>> affected. */
> >>> -	ret = axp288_adc_set_state(axp20x->regmap);
> >>> +	ret = regmap_write(info->regmap, AXP20X_ADC_EN1,
> >>> AXP288_ADC_EN_MASK); if (ret) {
> >>>  		dev_err(&pdev->dev, "unable to enable ADC
> >>> device\n"); return ret;
> >>>  
> >>  
> >
> > [Jacob Pan]
> >  

[Jacob Pan]
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Hans de Goede Jan. 3, 2017, 10:10 p.m. UTC | #6
Hi,

On 01/03/2017 07:23 PM, Jacob Pan wrote:
> On Sun, 1 Jan 2017 12:19:40 +0100
> Hans de Goede <hdegoede@redhat.com> wrote:
>
>> Hi,
>>
>> On 30-12-16 19:15, Jacob Pan wrote:
>>> On Fri, 30 Dec 2016 16:46:03 +0000
>>> Jonathan Cameron <jic23@kernel.org> wrote:
>>>
>>>> On 14/12/16 13:55, Hans de Goede wrote:
>>>>> For some reason the axp288_adc driver was modifying the
>>>>> AXP288_ADC_TS_PIN_CTRL register, changing bits 0-1 depending on
>>>>> whether the GP_ADC channel or another channel was written.
>>>>>
>>>>> These bits control when a bias current is send to the TS_PIN, the
>>>>> GP_ADC has its own pin and a separate bit in another register to
>>>>> control the bias current.
>>>>>
>>> It has been a while. Just looked at the datasheet, reg 84h is for
>>> ADC and TS pin control. IIRC, we had to set the TS bits in order to
>>> make ADC read to work.
>>
>> The bits the code I'm removing are manipulating are bits 0 & 1 of
>> reg 84h which are:
>>
>> 1-0 Current source from TS pin on/off enable bit [1:0]
>>
>> 00: off
>> 01: on when charging battery, off when not charging
>> 10: on in ADC phase and off when out of the ADC phase, for power
>> saving 11: always on
>>
>> And they are being toggled between 10 and 11, so in both
>> cases the current source is enabled when reading the adc
>> value. Specifically the code this patch removes are setting
>> these bits to 10 before reading and back to 11 after reading,
>> which makes no sense.
>>
>> And to make things even funkier, this manipulation is only
>> done when reading the GP_ADC, which is the ADC function of
>> GPIO0, whereas these bits control the bias current source
>> for the TS pin, which is a completely different pin.
>>
>> So all in all this entire bit of code seems to be big NOP.
>>
> It could have been a quirk we had to do on our platforms, I just
> cannot recall the details. Are you testing this on x86 platforms?

Yes, I've successfully tested this on 2 different models cherrytrail
tablets.

Regards,

Hans



>
>>> What is the other register?
>>
>> The register to actually enable / disable the bias current
>> source for GPIO0 / the GPADC pin is register 85h, where setting
>> bit 2 enables the GPIO0 output current.
>>
>> Regards,
>>
>> Hans
>>
>>
>>
>>>>> Not only does changing when to enable the TS_PIN bias current
>>>>> (always or only when sampling) when reading the GP_ADC make no
>>>>> sense at all, the code is modifying these bits is writing the
>>>>> entire register, assuming that all the other bits have their
>>>>> default value.
>>> Agreed, it would be better to do read-modify-write and not to
>>> touch the other bits.
>>>>> So if the firmware has configured a different bias-current for
>>>>> either pin, then that change gets clobbered by the write, likewise
>>>>> if the firmware has set bit 2 to indicate that the battery has no
>>>>> thermal sensor, this will get clobbered by the write.
>>>>>
>>>>> This commit fixes all this, by simply removing all writes to the
>>>>> AXP288_ADC_TS_PIN_CTRL register, they are not needed to read the
>>>>> GP_ADC pin, and can actually be harmful.
>>>>>
>>>>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>>>> I guess you probably have more up to date contact details than I
>>>> do, but seems worth trying to cc Jacob Pan on this to see if we
>>>> can find out what the original reasoning behind this was.  Seems a
>>>> very odd thing to do with no purpose!
>>>>
>>>> If Jacob isn't contactable we'll fall back to guessing it was just
>>>> an oddity of driver evolution.
>>>>
>>>> Jonathan
>>>>> ---
>>>>>  drivers/iio/adc/axp288_adc.c | 32
>>>>> +------------------------------- 1 file changed, 1 insertion(+),
>>>>> 31 deletions(-)
>>>>>
>>>>> diff --git a/drivers/iio/adc/axp288_adc.c
>>>>> b/drivers/iio/adc/axp288_adc.c index 7fd2494..64799ad 100644
>>>>> --- a/drivers/iio/adc/axp288_adc.c
>>>>> +++ b/drivers/iio/adc/axp288_adc.c
>>>>> @@ -28,8 +28,6 @@
>>>>>  #include <linux/iio/driver.h>
>>>>>
>>>>>  #define AXP288_ADC_EN_MASK		0xF1
>>>>> -#define AXP288_ADC_TS_PIN_GPADC		0xF2
>>>>> -#define AXP288_ADC_TS_PIN_ON		0xF3
>>>>>
>>>>>  enum axp288_adc_id {
>>>>>  	AXP288_ADC_TS,
>>>>> @@ -123,16 +121,6 @@ static int axp288_adc_read_channel(int *val,
>>>>> unsigned long address, return IIO_VAL_INT;
>>>>>  }
>>>>>
>>>>> -static int axp288_adc_set_ts(struct regmap *regmap, unsigned int
>>>>> mode,
>>>>> -				unsigned long address)
>>>>> -{
>>>>> -	/* channels other than GPADC do not need to switch TS pin
>>>>> */
>>>>> -	if (address != AXP288_GP_ADC_H)
>>>>> -		return 0;
>>>>> -
>>>>> -	return regmap_write(regmap, AXP288_ADC_TS_PIN_CTRL,
>>>>> mode); -}
>>>>> -
>>>>>  static int axp288_adc_read_raw(struct iio_dev *indio_dev,
>>>>>  			struct iio_chan_spec const *chan,
>>>>>  			int *val, int *val2, long mask)
>>>>> @@ -143,16 +131,7 @@ static int axp288_adc_read_raw(struct iio_dev
>>>>> *indio_dev, mutex_lock(&indio_dev->mlock);
>>>>>  	switch (mask) {
>>>>>  	case IIO_CHAN_INFO_RAW:
>>>>> -		if (axp288_adc_set_ts(info->regmap,
>>>>> AXP288_ADC_TS_PIN_GPADC,
>>>>> -					chan->address)) {
>>>>> -			dev_err(&indio_dev->dev, "GPADC mode\n");
>>>>> -			ret = -EINVAL;
>>>>> -			break;
>>>>> -		}
>>>>>  		ret = axp288_adc_read_channel(val, chan->address,
>>>>> info->regmap);
>>>>> -		if (axp288_adc_set_ts(info->regmap,
>>>>> AXP288_ADC_TS_PIN_ON,
>>>>> -						chan->address))
>>>>> -			dev_err(&indio_dev->dev, "TS pin
>>>>> restore\n"); break;
>>>>>  	default:
>>>>>  		ret = -EINVAL;
>>>>> @@ -162,15 +141,6 @@ static int axp288_adc_read_raw(struct iio_dev
>>>>> *indio_dev, return ret;
>>>>>  }
>>>>>
>>>>> -static int axp288_adc_set_state(struct regmap *regmap)
>>>>> -{
>>>>> -	/* ADC should be always enabled for internal FG to
>>>>> function */
>>>>> -	if (regmap_write(regmap, AXP288_ADC_TS_PIN_CTRL,
>>>>> AXP288_ADC_TS_PIN_ON))
>>>>> -		return -EIO;
>>>>> -
>>>>> -	return regmap_write(regmap, AXP20X_ADC_EN1,
>>>>> AXP288_ADC_EN_MASK); -}
>>>>> -
>>>>>  static const struct iio_info axp288_adc_iio_info = {
>>>>>  	.read_raw = &axp288_adc_read_raw,
>>>>>  	.driver_module = THIS_MODULE,
>>>>> @@ -199,7 +169,7 @@ static int axp288_adc_probe(struct
>>>>> platform_device *pdev)
>>>>>  	 * Set ADC to enabled state at all time, including system
>>>>> suspend.
>>>>>  	 * otherwise internal fuel gauge functionality may be
>>>>> affected. */
>>>>> -	ret = axp288_adc_set_state(axp20x->regmap);
>>>>> +	ret = regmap_write(info->regmap, AXP20X_ADC_EN1,
>>>>> AXP288_ADC_EN_MASK); if (ret) {
>>>>>  		dev_err(&pdev->dev, "unable to enable ADC
>>>>> device\n"); return ret;
>>>>>
>>>>
>>>
>>> [Jacob Pan]
>>>
>
> [Jacob Pan]
>
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Jacob Pan Jan. 4, 2017, 5:55 p.m. UTC | #7
On Tue, 3 Jan 2017 23:10:57 +0100
Hans de Goede <hdegoede@redhat.com> wrote:

> > It could have been a quirk we had to do on our platforms, I just
> > cannot recall the details. Are you testing this on x86 platforms?  
> 
> Yes, I've successfully tested this on 2 different models cherrytrail
> tablets.

[Jacob Pan] I am ok with your change. I last tested on baytrail
tablets, I don't know if you have one available to verify. That would
be ideal.

Thanks,
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Jonathan Cameron Jan. 7, 2017, 10:23 p.m. UTC | #8
On 04/01/17 17:55, Jacob Pan wrote:
> On Tue, 3 Jan 2017 23:10:57 +0100
> Hans de Goede <hdegoede@redhat.com> wrote:
> 
>>> It could have been a quirk we had to do on our platforms, I just
>>> cannot recall the details. Are you testing this on x86 platforms?  
>>
>> Yes, I've successfully tested this on 2 different models cherrytrail
>> tablets.
> 
> [Jacob Pan] I am ok with your change. I last tested on baytrail
> tablets, I don't know if you have one available to verify. That would
> be ideal.
> 
Stable material?  As I read this it is a fairly major fix, but we aren't
entirely sure there wasn't a reason on some platforms for this 'interesting'
corner of code?  

So basically are we sure this won't cause regressions? If so I'll take
it as a fix and mark for stable.

Thanks,

Jonathan
> Thanks,
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Hans de Goede Jan. 8, 2017, 10:15 a.m. UTC | #9
Hi,

On 07-01-17 23:23, Jonathan Cameron wrote:
> On 04/01/17 17:55, Jacob Pan wrote:
>> On Tue, 3 Jan 2017 23:10:57 +0100
>> Hans de Goede <hdegoede@redhat.com> wrote:
>>
>>>> It could have been a quirk we had to do on our platforms, I just
>>>> cannot recall the details. Are you testing this on x86 platforms?
>>>
>>> Yes, I've successfully tested this on 2 different models cherrytrail
>>> tablets.
>>
>> [Jacob Pan] I am ok with your change. I last tested on baytrail
>> tablets, I don't know if you have one available to verify. That would
>> be ideal.
>>
> Stable material?  As I read this it is a fairly major fix, but we aren't
> entirely sure there wasn't a reason on some platforms for this 'interesting'
> corner of code?
>
> So basically are we sure this won't cause regressions? If so I'll take
> it as a fix and mark for stable.

The main consumer of the axp288_adc code is the axp288_fuel_gauge driver,
which until now was not really functional. It depended on platform data
being attached to its mfd device, and the provider of that platform data
never got merged.

I've got patches queued up for 4.11 fixing this. So in practice the chance
of this patch causing regressions is close to 0 as so far it had no
consumers, likewise adding a Cc: stable is not really useful.

Regards,

Hans
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Jonathan Cameron Jan. 8, 2017, 10:34 a.m. UTC | #10
On 08/01/17 10:15, Hans de Goede wrote:
> Hi,
> 
> On 07-01-17 23:23, Jonathan Cameron wrote:
>> On 04/01/17 17:55, Jacob Pan wrote:
>>> On Tue, 3 Jan 2017 23:10:57 +0100
>>> Hans de Goede <hdegoede@redhat.com> wrote:
>>>
>>>>> It could have been a quirk we had to do on our platforms, I just
>>>>> cannot recall the details. Are you testing this on x86 platforms?
>>>>
>>>> Yes, I've successfully tested this on 2 different models cherrytrail
>>>> tablets.
>>>
>>> [Jacob Pan] I am ok with your change. I last tested on baytrail
>>> tablets, I don't know if you have one available to verify. That would
>>> be ideal.
>>>
>> Stable material?  As I read this it is a fairly major fix, but we aren't
>> entirely sure there wasn't a reason on some platforms for this 'interesting'
>> corner of code?
>>
>> So basically are we sure this won't cause regressions? If so I'll take
>> it as a fix and mark for stable.
> 
> The main consumer of the axp288_adc code is the axp288_fuel_gauge driver,
> which until now was not really functional. It depended on platform data
> being attached to its mfd device, and the provider of that platform data
> never got merged.
> 
> I've got patches queued up for 4.11 fixing this. So in practice the chance
> of this patch causing regressions is close to 0 as so far it had no
> consumers, likewise adding a Cc: stable is not really useful.
Cool. I'll queue it for 4.11 as well then.

Applied to the togreg branch of iio.git which will be pushed out as testing for
the autobuilders to play with it.

Thanks,

Jonathan
> 
> Regards,
> 
> Hans
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Patch
diff mbox

diff --git a/drivers/iio/adc/axp288_adc.c b/drivers/iio/adc/axp288_adc.c
index 7fd2494..64799ad 100644
--- a/drivers/iio/adc/axp288_adc.c
+++ b/drivers/iio/adc/axp288_adc.c
@@ -28,8 +28,6 @@ 
 #include <linux/iio/driver.h>
 
 #define AXP288_ADC_EN_MASK		0xF1
-#define AXP288_ADC_TS_PIN_GPADC		0xF2
-#define AXP288_ADC_TS_PIN_ON		0xF3
 
 enum axp288_adc_id {
 	AXP288_ADC_TS,
@@ -123,16 +121,6 @@  static int axp288_adc_read_channel(int *val, unsigned long address,
 	return IIO_VAL_INT;
 }
 
-static int axp288_adc_set_ts(struct regmap *regmap, unsigned int mode,
-				unsigned long address)
-{
-	/* channels other than GPADC do not need to switch TS pin */
-	if (address != AXP288_GP_ADC_H)
-		return 0;
-
-	return regmap_write(regmap, AXP288_ADC_TS_PIN_CTRL, mode);
-}
-
 static int axp288_adc_read_raw(struct iio_dev *indio_dev,
 			struct iio_chan_spec const *chan,
 			int *val, int *val2, long mask)
@@ -143,16 +131,7 @@  static int axp288_adc_read_raw(struct iio_dev *indio_dev,
 	mutex_lock(&indio_dev->mlock);
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
-		if (axp288_adc_set_ts(info->regmap, AXP288_ADC_TS_PIN_GPADC,
-					chan->address)) {
-			dev_err(&indio_dev->dev, "GPADC mode\n");
-			ret = -EINVAL;
-			break;
-		}
 		ret = axp288_adc_read_channel(val, chan->address, info->regmap);
-		if (axp288_adc_set_ts(info->regmap, AXP288_ADC_TS_PIN_ON,
-						chan->address))
-			dev_err(&indio_dev->dev, "TS pin restore\n");
 		break;
 	default:
 		ret = -EINVAL;
@@ -162,15 +141,6 @@  static int axp288_adc_read_raw(struct iio_dev *indio_dev,
 	return ret;
 }
 
-static int axp288_adc_set_state(struct regmap *regmap)
-{
-	/* ADC should be always enabled for internal FG to function */
-	if (regmap_write(regmap, AXP288_ADC_TS_PIN_CTRL, AXP288_ADC_TS_PIN_ON))
-		return -EIO;
-
-	return regmap_write(regmap, AXP20X_ADC_EN1, AXP288_ADC_EN_MASK);
-}
-
 static const struct iio_info axp288_adc_iio_info = {
 	.read_raw = &axp288_adc_read_raw,
 	.driver_module = THIS_MODULE,
@@ -199,7 +169,7 @@  static int axp288_adc_probe(struct platform_device *pdev)
 	 * Set ADC to enabled state at all time, including system suspend.
 	 * otherwise internal fuel gauge functionality may be affected.
 	 */
-	ret = axp288_adc_set_state(axp20x->regmap);
+	ret = regmap_write(info->regmap, AXP20X_ADC_EN1, AXP288_ADC_EN_MASK);
 	if (ret) {
 		dev_err(&pdev->dev, "unable to enable ADC device\n");
 		return ret;