diff mbox

[v2,07/16] iio: adc: sun4i-gpadc-iio: rework: support nvmem calibration data

Message ID 20180128232919.12639-8-embed3d@gmail.com (mailing list archive)
State New, archived
Headers show

Commit Message

Philipp Rossak Jan. 28, 2018, 11:29 p.m. UTC
This patch reworks the driver to support nvmem calibration cells.
The driver checks if the nvmem calibration is supported and reads out
the nvmem.

Signed-off-by: Philipp Rossak <embed3d@gmail.com>
---
 drivers/iio/adc/sun4i-gpadc-iio.c | 44 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

Comments

Maxime Ripard Jan. 29, 2018, 9:40 a.m. UTC | #1
On Mon, Jan 29, 2018 at 12:29:10AM +0100, Philipp Rossak wrote:
> This patch reworks the driver to support nvmem calibration cells.
> The driver checks if the nvmem calibration is supported and reads out
> the nvmem.
> 
> Signed-off-by: Philipp Rossak <embed3d@gmail.com>
> ---
>  drivers/iio/adc/sun4i-gpadc-iio.c | 44 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
> 
> diff --git a/drivers/iio/adc/sun4i-gpadc-iio.c b/drivers/iio/adc/sun4i-gpadc-iio.c
> index ac9ad2f8232f..74eeb5cd5218 100644
> --- a/drivers/iio/adc/sun4i-gpadc-iio.c
> +++ b/drivers/iio/adc/sun4i-gpadc-iio.c
> @@ -27,6 +27,7 @@
>  #include <linux/interrupt.h>
>  #include <linux/io.h>
>  #include <linux/module.h>
> +#include <linux/nvmem-consumer.h>
>  #include <linux/of.h>
>  #include <linux/of_device.h>
>  #include <linux/platform_device.h>
> @@ -74,6 +75,7 @@ struct gpadc_data {
>  	bool		has_bus_rst;
>  	bool		has_mod_clk;
>  	int		sensor_count;
> +	bool		supports_nvmem;

I think you should add some documentation along with all the fields
you're adding.

>  };
>  
>  static const struct gpadc_data sun4i_gpadc_data = {
> @@ -87,6 +89,7 @@ static const struct gpadc_data sun4i_gpadc_data = {
>  	.sample_start = sun4i_gpadc_sample_start,
>  	.sample_end = sun4i_gpadc_sample_end,
>  	.sensor_count = 1,
> +	.supports_nvmem = false,

That's already its value if you leave it out.

>  };
>  
>  static const struct gpadc_data sun5i_gpadc_data = {
> @@ -100,6 +103,7 @@ static const struct gpadc_data sun5i_gpadc_data = {
>  	.sample_start = sun4i_gpadc_sample_start,
>  	.sample_end = sun4i_gpadc_sample_end,
>  	.sensor_count = 1,
> +	.supports_nvmem = false,
>  };
>  
>  static const struct gpadc_data sun6i_gpadc_data = {
> @@ -113,6 +117,7 @@ static const struct gpadc_data sun6i_gpadc_data = {
>  	.sample_start = sun4i_gpadc_sample_start,
>  	.sample_end = sun4i_gpadc_sample_end,
>  	.sensor_count = 1,
> +	.supports_nvmem = false,
>  };
>  
>  static const struct gpadc_data sun8i_a33_gpadc_data = {
> @@ -123,6 +128,7 @@ static const struct gpadc_data sun8i_a33_gpadc_data = {
>  	.sample_start = sun4i_gpadc_sample_start,
>  	.sample_end = sun4i_gpadc_sample_end,
>  	.sensor_count = 1,
> +	.supports_nvmem = false,
>  };
>  
>  struct sun4i_gpadc_iio {
> @@ -141,6 +147,8 @@ struct sun4i_gpadc_iio {
>  	struct clk			*mod_clk;
>  	struct reset_control		*reset;
>  	int				sensor_id;
> +	u32				calibration_data[2];
> +	bool				has_calibration_data[2];

Why do you have two different values here?

>  	/* prevents concurrent reads of temperature and ADC */
>  	struct mutex			mutex;
>  	struct thermal_zone_device	*tzd;
> @@ -561,6 +569,9 @@ static int sun4i_gpadc_probe_dt(struct platform_device *pdev,
>  	struct resource *mem;
>  	void __iomem *base;
>  	int ret;
> +	struct nvmem_cell *cell;
> +	ssize_t cell_size;
> +	u64 *cell_data;
>  
>  	info->data = of_device_get_match_data(&pdev->dev);
>  	if (!info->data)
> @@ -575,6 +586,39 @@ static int sun4i_gpadc_probe_dt(struct platform_device *pdev,
>  	if (IS_ERR(base))
>  		return PTR_ERR(base);
>  
> +	info->has_calibration_data[0] = false;
> +	info->has_calibration_data[1] = false;
> +
> +	if (!info->data->supports_nvmem)
> +		goto no_nvmem;
> +
> +	cell = nvmem_cell_get(&pdev->dev, "calibration");
> +	if (IS_ERR(cell)) {
> +		if (PTR_ERR(cell) == -EPROBE_DEFER)
> +			return PTR_ERR(cell);
> +		goto no_nvmem;

goto considered evil ? :)

> +	}
> +
> +	cell_data = (u64 *)nvmem_cell_read(cell, &cell_size);
> +	nvmem_cell_put(cell);
> +	switch (cell_size) {
> +		case 8:
> +		case 6:
> +			info->has_calibration_data[1] = true;
> +			info->calibration_data[1] = be32_to_cpu(
> +					upper_32_bits(cell_data[0]));
> +		case 4:
> +		case 2:
> +			info->has_calibration_data[0] = true;
> +			info->calibration_data[0] = be32_to_cpu(
> +					lower_32_bits(cell_data[0]));

Why do you need that switch?

Thanks!
Maxime
Philipp Rossak Jan. 29, 2018, 12:33 p.m. UTC | #2
On 29.01.2018 10:40, Maxime Ripard wrote:
> On Mon, Jan 29, 2018 at 12:29:10AM +0100, Philipp Rossak wrote:
>> This patch reworks the driver to support nvmem calibration cells.
>> The driver checks if the nvmem calibration is supported and reads out
>> the nvmem.
>>
>> Signed-off-by: Philipp Rossak <embed3d@gmail.com>
>> ---
>>   drivers/iio/adc/sun4i-gpadc-iio.c | 44 +++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 44 insertions(+)
>>
>> diff --git a/drivers/iio/adc/sun4i-gpadc-iio.c b/drivers/iio/adc/sun4i-gpadc-iio.c
>> index ac9ad2f8232f..74eeb5cd5218 100644
>> --- a/drivers/iio/adc/sun4i-gpadc-iio.c
>> +++ b/drivers/iio/adc/sun4i-gpadc-iio.c
>> @@ -27,6 +27,7 @@
>>   #include <linux/interrupt.h>
>>   #include <linux/io.h>
>>   #include <linux/module.h>
>> +#include <linux/nvmem-consumer.h>
>>   #include <linux/of.h>
>>   #include <linux/of_device.h>
>>   #include <linux/platform_device.h>
>> @@ -74,6 +75,7 @@ struct gpadc_data {
>>   	bool		has_bus_rst;
>>   	bool		has_mod_clk;
>>   	int		sensor_count;
>> +	bool		supports_nvmem;
> 
> I think you should add some documentation along with all the fields
> you're adding.

ok I will add more informations in the next version into the commit message.

> 
>>   };
>>   
>>   static const struct gpadc_data sun4i_gpadc_data = {
>> @@ -87,6 +89,7 @@ static const struct gpadc_data sun4i_gpadc_data = {
>>   	.sample_start = sun4i_gpadc_sample_start,
>>   	.sample_end = sun4i_gpadc_sample_end,
>>   	.sensor_count = 1,
>> +	.supports_nvmem = false,
> 
> That's already its value if you leave it out.
> 
>>   };
>>   
>>   static const struct gpadc_data sun5i_gpadc_data = {
>> @@ -100,6 +103,7 @@ static const struct gpadc_data sun5i_gpadc_data = {
>>   	.sample_start = sun4i_gpadc_sample_start,
>>   	.sample_end = sun4i_gpadc_sample_end,
>>   	.sensor_count = 1,
>> +	.supports_nvmem = false,
>>   };
>>   
>>   static const struct gpadc_data sun6i_gpadc_data = {
>> @@ -113,6 +117,7 @@ static const struct gpadc_data sun6i_gpadc_data = {
>>   	.sample_start = sun4i_gpadc_sample_start,
>>   	.sample_end = sun4i_gpadc_sample_end,
>>   	.sensor_count = 1,
>> +	.supports_nvmem = false,
>>   };
>>   
>>   static const struct gpadc_data sun8i_a33_gpadc_data = {
>> @@ -123,6 +128,7 @@ static const struct gpadc_data sun8i_a33_gpadc_data = {
>>   	.sample_start = sun4i_gpadc_sample_start,
>>   	.sample_end = sun4i_gpadc_sample_end,
>>   	.sensor_count = 1,
>> +	.supports_nvmem = false,
>>   };
>>   
>>   struct sun4i_gpadc_iio {
>> @@ -141,6 +147,8 @@ struct sun4i_gpadc_iio {
>>   	struct clk			*mod_clk;
>>   	struct reset_control		*reset;
>>   	int				sensor_id;
>> +	u32				calibration_data[2];
>> +	bool				has_calibration_data[2];
> 
> Why do you have two different values here?
> 

I think my idea was too complex! I thought it would be better to check 
if calibration data was read, and is able to be written to hardware. 
those information were split per register.

I think a u64 should be fine for calibration_data. When I write the 
calibration data I can check on the sensor count and write only the 
lower 32 bits if there are less than 3 sensors.

Is this ok for you?


>>   	/* prevents concurrent reads of temperature and ADC */
>>   	struct mutex			mutex;
>>   	struct thermal_zone_device	*tzd;
>> @@ -561,6 +569,9 @@ static int sun4i_gpadc_probe_dt(struct platform_device *pdev,
>>   	struct resource *mem;
>>   	void __iomem *base;
>>   	int ret;
>> +	struct nvmem_cell *cell;
>> +	ssize_t cell_size;
>> +	u64 *cell_data;
>>   
>>   	info->data = of_device_get_match_data(&pdev->dev);
>>   	if (!info->data)
>> @@ -575,6 +586,39 @@ static int sun4i_gpadc_probe_dt(struct platform_device *pdev,
>>   	if (IS_ERR(base))
>>   		return PTR_ERR(base);
>>   
>> +	info->has_calibration_data[0] = false;
>> +	info->has_calibration_data[1] = false;
>> +
>> +	if (!info->data->supports_nvmem)
>> +		goto no_nvmem;
>> +
>> +	cell = nvmem_cell_get(&pdev->dev, "calibration");
>> +	if (IS_ERR(cell)) {
>> +		if (PTR_ERR(cell) == -EPROBE_DEFER)
>> +			return PTR_ERR(cell);
>> +		goto no_nvmem;
> 
> goto considered evil ? :)
> 

this was a suggestion from Jonatan in version one, to make the code 
better readable.
.
>> +	}
>> +
>> +	cell_data = (u64 *)nvmem_cell_read(cell, &cell_size);
>> +	nvmem_cell_put(cell);
>> +	switch (cell_size) {
>> +		case 8:
>> +		case 6:
>> +			info->has_calibration_data[1] = true;
>> +			info->calibration_data[1] = be32_to_cpu(
>> +					upper_32_bits(cell_data[0]));
>> +		case 4:
>> +		case 2:
>> +			info->has_calibration_data[0] = true;
>> +			info->calibration_data[0] = be32_to_cpu(
>> +					lower_32_bits(cell_data[0]));
> 
> Why do you need that switch?

You are right! The calibration reg seems to be always 64 bit wide. [1]
So I will just check for the length of 8.


> 
> Thanks!
> Maxime
> 

[1]: http://linux-sunxi.org/SID_Register_Guide#eFUSE

Thanks,
Philipp
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Maxime Ripard Jan. 30, 2018, 8:36 a.m. UTC | #3
On Mon, Jan 29, 2018 at 01:33:12PM +0100, Philipp Rossak wrote:
> > >   static const struct gpadc_data sun4i_gpadc_data = {
> > > @@ -87,6 +89,7 @@ static const struct gpadc_data sun4i_gpadc_data = {
> > >   	.sample_start = sun4i_gpadc_sample_start,
> > >   	.sample_end = sun4i_gpadc_sample_end,
> > >   	.sensor_count = 1,
> > > +	.supports_nvmem = false,
> > 
> > That's already its value if you leave it out.
> > 
> > >   };
> > >   static const struct gpadc_data sun5i_gpadc_data = {
> > > @@ -100,6 +103,7 @@ static const struct gpadc_data sun5i_gpadc_data = {
> > >   	.sample_start = sun4i_gpadc_sample_start,
> > >   	.sample_end = sun4i_gpadc_sample_end,
> > >   	.sensor_count = 1,
> > > +	.supports_nvmem = false,
> > >   };
> > >   static const struct gpadc_data sun6i_gpadc_data = {
> > > @@ -113,6 +117,7 @@ static const struct gpadc_data sun6i_gpadc_data = {
> > >   	.sample_start = sun4i_gpadc_sample_start,
> > >   	.sample_end = sun4i_gpadc_sample_end,
> > >   	.sensor_count = 1,
> > > +	.supports_nvmem = false,
> > >   };
> > >   static const struct gpadc_data sun8i_a33_gpadc_data = {
> > > @@ -123,6 +128,7 @@ static const struct gpadc_data sun8i_a33_gpadc_data = {
> > >   	.sample_start = sun4i_gpadc_sample_start,
> > >   	.sample_end = sun4i_gpadc_sample_end,
> > >   	.sensor_count = 1,
> > > +	.supports_nvmem = false,
> > >   };
> > >   struct sun4i_gpadc_iio {
> > > @@ -141,6 +147,8 @@ struct sun4i_gpadc_iio {
> > >   	struct clk			*mod_clk;
> > >   	struct reset_control		*reset;
> > >   	int				sensor_id;
> > > +	u32				calibration_data[2];
> > > +	bool				has_calibration_data[2];
> > 
> > Why do you have two different values here?
> 
> I think my idea was too complex! I thought it would be better to check if
> calibration data was read, and is able to be written to hardware. those
> information were split per register.
> 
> I think a u64 should be fine for calibration_data. When I write the
> calibration data I can check on the sensor count and write only the lower 32
> bits if there are less than 3 sensors.
> 
> Is this ok for you?

I'd need to see the implementation, but make sure that this is
documented in your driver :)

> 
> > >   	/* prevents concurrent reads of temperature and ADC */
> > >   	struct mutex			mutex;
> > >   	struct thermal_zone_device	*tzd;
> > > @@ -561,6 +569,9 @@ static int sun4i_gpadc_probe_dt(struct platform_device *pdev,
> > >   	struct resource *mem;
> > >   	void __iomem *base;
> > >   	int ret;
> > > +	struct nvmem_cell *cell;
> > > +	ssize_t cell_size;
> > > +	u64 *cell_data;
> > >   	info->data = of_device_get_match_data(&pdev->dev);
> > >   	if (!info->data)
> > > @@ -575,6 +586,39 @@ static int sun4i_gpadc_probe_dt(struct platform_device *pdev,
> > >   	if (IS_ERR(base))
> > >   		return PTR_ERR(base);
> > > +	info->has_calibration_data[0] = false;
> > > +	info->has_calibration_data[1] = false;
> > > +
> > > +	if (!info->data->supports_nvmem)
> > > +		goto no_nvmem;
> > > +
> > > +	cell = nvmem_cell_get(&pdev->dev, "calibration");
> > > +	if (IS_ERR(cell)) {
> > > +		if (PTR_ERR(cell) == -EPROBE_DEFER)
> > > +			return PTR_ERR(cell);
> > > +		goto no_nvmem;
> > 
> > goto considered evil ? :)
> 
> this was a suggestion from Jonatan in version one, to make the code better
> readable.

Isn't

if (info->data->supports_nvmem && IS_ERR(cell = nvmem_cell_get()))

pretty much the same thing?

Maxime
kernel test robot Jan. 31, 2018, 10:49 p.m. UTC | #4
Hi Philipp,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on robh/for-next]
[also build test WARNING on v4.15 next-20180126]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Philipp-Rossak/IIO-based-thermal-sensor-driver-for-Allwinner-H3-and-A83T-SoC/20180201-043415
base:   https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git for-next
reproduce:
        # apt-get install sparse
        make ARCH=x86_64 allmodconfig
        make C=1 CF=-D__CHECK_ENDIAN__


sparse warnings: (new ones prefixed by >>)

>> drivers/iio/adc/sun4i-gpadc-iio.c:608:53: sparse: cast to restricted __be32
>> drivers/iio/adc/sun4i-gpadc-iio.c:608:53: sparse: cast to restricted __be32
>> drivers/iio/adc/sun4i-gpadc-iio.c:608:53: sparse: cast to restricted __be32
>> drivers/iio/adc/sun4i-gpadc-iio.c:608:53: sparse: cast to restricted __be32
>> drivers/iio/adc/sun4i-gpadc-iio.c:608:53: sparse: cast to restricted __be32
>> drivers/iio/adc/sun4i-gpadc-iio.c:608:53: sparse: cast to restricted __be32
   drivers/iio/adc/sun4i-gpadc-iio.c:613:53: sparse: cast to restricted __be32
   drivers/iio/adc/sun4i-gpadc-iio.c:613:53: sparse: cast to restricted __be32
   drivers/iio/adc/sun4i-gpadc-iio.c:613:53: sparse: cast to restricted __be32
   drivers/iio/adc/sun4i-gpadc-iio.c:613:53: sparse: cast to restricted __be32
   drivers/iio/adc/sun4i-gpadc-iio.c:613:53: sparse: cast to restricted __be32
   drivers/iio/adc/sun4i-gpadc-iio.c:613:53: sparse: cast to restricted __be32

vim +608 drivers/iio/adc/sun4i-gpadc-iio.c

   564	
   565	static int sun4i_gpadc_probe_dt(struct platform_device *pdev,
   566					struct iio_dev *indio_dev)
   567	{
   568		struct sun4i_gpadc_iio *info = iio_priv(indio_dev);
   569		struct resource *mem;
   570		void __iomem *base;
   571		int ret;
   572		struct nvmem_cell *cell;
   573		ssize_t cell_size;
   574		u64 *cell_data;
   575	
   576		info->data = of_device_get_match_data(&pdev->dev);
   577		if (!info->data)
   578			return -ENODEV;
   579	
   580		info->no_irq = true;
   581		indio_dev->num_channels = ARRAY_SIZE(sun8i_a33_gpadc_channels);
   582		indio_dev->channels = sun8i_a33_gpadc_channels;
   583	
   584		mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
   585		base = devm_ioremap_resource(&pdev->dev, mem);
   586		if (IS_ERR(base))
   587			return PTR_ERR(base);
   588	
   589		info->has_calibration_data[0] = false;
   590		info->has_calibration_data[1] = false;
   591	
   592		if (!info->data->supports_nvmem)
   593			goto no_nvmem;
   594	
   595		cell = nvmem_cell_get(&pdev->dev, "calibration");
   596		if (IS_ERR(cell)) {
   597			if (PTR_ERR(cell) == -EPROBE_DEFER)
   598				return PTR_ERR(cell);
   599			goto no_nvmem;
   600		}
   601	
   602		cell_data = (u64 *)nvmem_cell_read(cell, &cell_size);
   603		nvmem_cell_put(cell);
   604		switch (cell_size) {
   605			case 8:
   606			case 6:
   607				info->has_calibration_data[1] = true;
 > 608				info->calibration_data[1] = be32_to_cpu(
   609						upper_32_bits(cell_data[0]));
   610			case 4:
   611			case 2:
   612				info->has_calibration_data[0] = true;
   613				info->calibration_data[0] = be32_to_cpu(
   614						lower_32_bits(cell_data[0]));
   615				break;
   616			default:
   617				break;
   618		}
   619	
   620	no_nvmem:
   621	
   622		info->regmap = devm_regmap_init_mmio(&pdev->dev, base,
   623						     &sun4i_gpadc_regmap_config);
   624		if (IS_ERR(info->regmap)) {
   625			ret = PTR_ERR(info->regmap);
   626			dev_err(&pdev->dev, "failed to init regmap: %d\n", ret);
   627			return ret;
   628		}
   629	
   630		if (info->data->has_bus_rst) {
   631			info->reset = devm_reset_control_get(&pdev->dev, NULL);
   632			if (IS_ERR(info->reset)) {
   633				ret = PTR_ERR(info->reset);
   634				return ret;
   635			}
   636	
   637			ret = reset_control_deassert(info->reset);
   638			if (ret)
   639				return ret;
   640		}
   641	
   642		if (info->data->has_bus_clk) {
   643			info->bus_clk = devm_clk_get(&pdev->dev, "bus");
   644			if (IS_ERR(info->bus_clk)) {
   645				ret = PTR_ERR(info->bus_clk);
   646				goto assert_reset;
   647			}
   648	
   649			ret = clk_prepare_enable(info->bus_clk);
   650			if (ret)
   651				goto assert_reset;
   652		}
   653	
   654		if (info->data->has_mod_clk) {
   655			info->mod_clk = devm_clk_get(&pdev->dev, "mod");
   656			if (IS_ERR(info->mod_clk)) {
   657				ret = PTR_ERR(info->mod_clk);
   658				goto disable_bus_clk;
   659			}
   660	
   661			/* Running at 6MHz */
   662			ret = clk_set_rate(info->mod_clk, 4000000);
   663			if (ret)
   664				goto disable_bus_clk;
   665	
   666			ret = clk_prepare_enable(info->mod_clk);
   667			if (ret)
   668				goto disable_bus_clk;
   669		}
   670	
   671		if (IS_ENABLED(CONFIG_THERMAL_OF))
   672			info->sensor_device = &pdev->dev;
   673	
   674		return 0;
   675	
   676	disable_bus_clk:
   677		clk_disable_unprepare(info->bus_clk);
   678	
   679	assert_reset:
   680		reset_control_assert(info->reset);
   681	
   682		return ret;
   683	}
   684	

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Philipp Rossak Feb. 2, 2018, 3:24 p.m. UTC | #5
>>
>>>>    	/* prevents concurrent reads of temperature and ADC */
>>>>    	struct mutex			mutex;
>>>>    	struct thermal_zone_device	*tzd;
>>>> @@ -561,6 +569,9 @@ static int sun4i_gpadc_probe_dt(struct platform_device *pdev,
>>>>    	struct resource *mem;
>>>>    	void __iomem *base;
>>>>    	int ret;
>>>> +	struct nvmem_cell *cell;
>>>> +	ssize_t cell_size;
>>>> +	u64 *cell_data;
>>>>    	info->data = of_device_get_match_data(&pdev->dev);
>>>>    	if (!info->data)
>>>> @@ -575,6 +586,39 @@ static int sun4i_gpadc_probe_dt(struct platform_device *pdev,
>>>>    	if (IS_ERR(base))
>>>>    		return PTR_ERR(base);
>>>> +	info->has_calibration_data[0] = false;
>>>> +	info->has_calibration_data[1] = false;
>>>> +
>>>> +	if (!info->data->supports_nvmem)
>>>> +		goto no_nvmem;
>>>> +
>>>> +	cell = nvmem_cell_get(&pdev->dev, "calibration");
>>>> +	if (IS_ERR(cell)) {
>>>> +		if (PTR_ERR(cell) == -EPROBE_DEFER)
>>>> +			return PTR_ERR(cell);
>>>> +		goto no_nvmem;
>>>
>>> goto considered evil ? :)
>>
>> this was a suggestion from Jonatan in version one, to make the code better
>> readable.
> 
> Isn't
> 
> if (info->data->supports_nvmem && IS_ERR(cell = nvmem_cell_get()))
> 
> pretty much the same thing?
> 
> Maxime
> 
I would say :

if (info->data->supports_nvmem && !IS_ERR(cell = nvmem_cell_get())) is

the same.
This would require an else if statement like this:

else if (info->data->supports_nvmem && PTR_ERR(cell) == -EPROBE_DEFER)
		return PTR_ERR(cell);

to avoid errors if the thermal sensor is probed before the sid driver.

Philipp
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diff mbox

Patch

diff --git a/drivers/iio/adc/sun4i-gpadc-iio.c b/drivers/iio/adc/sun4i-gpadc-iio.c
index ac9ad2f8232f..74eeb5cd5218 100644
--- a/drivers/iio/adc/sun4i-gpadc-iio.c
+++ b/drivers/iio/adc/sun4i-gpadc-iio.c
@@ -27,6 +27,7 @@ 
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/module.h>
+#include <linux/nvmem-consumer.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
@@ -74,6 +75,7 @@  struct gpadc_data {
 	bool		has_bus_rst;
 	bool		has_mod_clk;
 	int		sensor_count;
+	bool		supports_nvmem;
 };
 
 static const struct gpadc_data sun4i_gpadc_data = {
@@ -87,6 +89,7 @@  static const struct gpadc_data sun4i_gpadc_data = {
 	.sample_start = sun4i_gpadc_sample_start,
 	.sample_end = sun4i_gpadc_sample_end,
 	.sensor_count = 1,
+	.supports_nvmem = false,
 };
 
 static const struct gpadc_data sun5i_gpadc_data = {
@@ -100,6 +103,7 @@  static const struct gpadc_data sun5i_gpadc_data = {
 	.sample_start = sun4i_gpadc_sample_start,
 	.sample_end = sun4i_gpadc_sample_end,
 	.sensor_count = 1,
+	.supports_nvmem = false,
 };
 
 static const struct gpadc_data sun6i_gpadc_data = {
@@ -113,6 +117,7 @@  static const struct gpadc_data sun6i_gpadc_data = {
 	.sample_start = sun4i_gpadc_sample_start,
 	.sample_end = sun4i_gpadc_sample_end,
 	.sensor_count = 1,
+	.supports_nvmem = false,
 };
 
 static const struct gpadc_data sun8i_a33_gpadc_data = {
@@ -123,6 +128,7 @@  static const struct gpadc_data sun8i_a33_gpadc_data = {
 	.sample_start = sun4i_gpadc_sample_start,
 	.sample_end = sun4i_gpadc_sample_end,
 	.sensor_count = 1,
+	.supports_nvmem = false,
 };
 
 struct sun4i_gpadc_iio {
@@ -141,6 +147,8 @@  struct sun4i_gpadc_iio {
 	struct clk			*mod_clk;
 	struct reset_control		*reset;
 	int				sensor_id;
+	u32				calibration_data[2];
+	bool				has_calibration_data[2];
 	/* prevents concurrent reads of temperature and ADC */
 	struct mutex			mutex;
 	struct thermal_zone_device	*tzd;
@@ -561,6 +569,9 @@  static int sun4i_gpadc_probe_dt(struct platform_device *pdev,
 	struct resource *mem;
 	void __iomem *base;
 	int ret;
+	struct nvmem_cell *cell;
+	ssize_t cell_size;
+	u64 *cell_data;
 
 	info->data = of_device_get_match_data(&pdev->dev);
 	if (!info->data)
@@ -575,6 +586,39 @@  static int sun4i_gpadc_probe_dt(struct platform_device *pdev,
 	if (IS_ERR(base))
 		return PTR_ERR(base);
 
+	info->has_calibration_data[0] = false;
+	info->has_calibration_data[1] = false;
+
+	if (!info->data->supports_nvmem)
+		goto no_nvmem;
+
+	cell = nvmem_cell_get(&pdev->dev, "calibration");
+	if (IS_ERR(cell)) {
+		if (PTR_ERR(cell) == -EPROBE_DEFER)
+			return PTR_ERR(cell);
+		goto no_nvmem;
+	}
+
+	cell_data = (u64 *)nvmem_cell_read(cell, &cell_size);
+	nvmem_cell_put(cell);
+	switch (cell_size) {
+		case 8:
+		case 6:
+			info->has_calibration_data[1] = true;
+			info->calibration_data[1] = be32_to_cpu(
+					upper_32_bits(cell_data[0]));
+		case 4:
+		case 2:
+			info->has_calibration_data[0] = true;
+			info->calibration_data[0] = be32_to_cpu(
+					lower_32_bits(cell_data[0]));
+			break;
+		default:
+			break;
+	}
+
+no_nvmem:
+
 	info->regmap = devm_regmap_init_mmio(&pdev->dev, base,
 					     &sun4i_gpadc_regmap_config);
 	if (IS_ERR(info->regmap)) {