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Subject: Re: [PATCH v2 07/16] iio: adc: sun4i-gpadc-iio: rework: support nvmem
 calibration data
To:     Maxime Ripard <maxime.ripard@free-electrons.com>
Cc:     lee.jones@linaro.org, robh+dt@kernel.org, mark.rutland@arm.com,
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        davem@davemloft.net, hans.verkuil@cisco.com, mchehab@kernel.org,
        rask@formelder.dk, clabbe.montjoie@gmail.com, sean@mess.org,
        krzk@kernel.org, quentin.schulz@free-electrons.com,
        icenowy@aosc.io, edu.molinas@gmail.com, singhalsimran0@gmail.com,
        linux-iio@vger.kernel.org, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-sunxi@googlegroups.com
References: <20180128232919.12639-1-embed3d@gmail.com>
 <20180128232919.12639-8-embed3d@gmail.com>
 <20180129094045.sagz2dnzvdadd4yx@flea.lan>
From:   Philipp Rossak <embed3d@gmail.com>
Message-ID: <e319fde5-9ede-8be0-03ae-f0a22d50250c@gmail.com>
Date:   Mon, 29 Jan 2018 13:33:12 +0100
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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