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

[Philipp Rossak]

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@xxxxxxxxx>
> > ---
> >   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