On Fri, 24 Aug 2018 17:53:16 +0800
Baolin Wang <baolin.w...@linaro.org> wrote:
> This patch adds support to read calibration values from the eFuse
> controller to calibrate the ADC channel scales, which can make ADC
> sample data more accurate.
>
> Signed-off-by: Baolin Wang <baolin.w...@linaro.org>
This looks good to me. I'll leave it for now though given open questions
on patch 1 and to allow others time to comment on this if they wish -
particularly as it includes a binding addition.
Jonathan
> ---
> .../bindings/iio/adc/sprd,sc27xx-adc.txt | 4 ++
> drivers/iio/adc/sc27xx_adc.c | 52
> ++++++++++++++++++--
> 2 files changed, 53 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/iio/adc/sprd,sc27xx-adc.txt
> b/Documentation/devicetree/bindings/iio/adc/sprd,sc27xx-adc.txt
> index 8aad960..b4daa15 100644
> --- a/Documentation/devicetree/bindings/iio/adc/sprd,sc27xx-adc.txt
> +++ b/Documentation/devicetree/bindings/iio/adc/sprd,sc27xx-adc.txt
> @@ -12,6 +12,8 @@ Required properties:
> - interrupts: The interrupt number for the ADC device.
> - #io-channel-cells: Number of cells in an IIO specifier.
> - hwlocks: Reference to a phandle of a hwlock provider node.
> +- nvmem-cells: A phandle to the calibration cells provided by eFuse device.
> +- nvmem-cell-names: Should be "big_scale_calib", "small_scale_calib".
>
> Example:
>
> @@ -32,5 +34,7 @@ Example:
> interrupts = <0 IRQ_TYPE_LEVEL_HIGH>;
> #io-channel-cells = <1>;
> hwlocks = <&hwlock 4>;
> + nvmem-cells = <&adc_big_scale>, <&adc_small_scale>;
> + nvmem-cell-names = "big_scale_calib",
> "small_scale_calib";
> };
> };
> diff --git a/drivers/iio/adc/sc27xx_adc.c b/drivers/iio/adc/sc27xx_adc.c
> index 153c311..7ac78eda 100644
> --- a/drivers/iio/adc/sc27xx_adc.c
> +++ b/drivers/iio/adc/sc27xx_adc.c
> @@ -5,6 +5,7 @@
> #include <linux/iio/iio.h>
> #include <linux/interrupt.h>
> #include <linux/module.h>
> +#include <linux/nvmem-consumer.h>
> #include <linux/of.h>
> #include <linux/of_device.h>
> #include <linux/platform_device.h>
> @@ -87,16 +88,48 @@ struct sc27xx_adc_linear_graph {
> * should use the small-scale graph, and if more than 1.2v, we should use the
> * big-scale graph.
> */
> -static const struct sc27xx_adc_linear_graph big_scale_graph = {
> +static struct sc27xx_adc_linear_graph big_scale_graph = {
> 4200, 3310,
> 3600, 2832,
> };
>
> -static const struct sc27xx_adc_linear_graph small_scale_graph = {
> +static struct sc27xx_adc_linear_graph small_scale_graph = {
> 1000, 3413,
> 100, 341,
> };
>
> +static const struct sc27xx_adc_linear_graph big_scale_graph_calib = {
> + 4200, 856,
> + 3600, 733,
> +};
> +
> +static const struct sc27xx_adc_linear_graph small_scale_graph_calib = {
> + 1000, 833,
> + 100, 80,
> +};
> +
> +static int sc27xx_adc_get_calib_data(u32 calib_data, int calib_adc)
> +{
> + return ((calib_data & 0xff) + calib_adc - 128) * 4;
> +}
> +
> +static void
> +sc27xx_adc_scale_calibration(const struct sc27xx_adc_linear_graph
> *calib_graph,
> + u32 calib_data, bool big_scale)
> +{
> + struct sc27xx_adc_linear_graph *graph;
> +
> + if (big_scale)
> + graph = &big_scale_graph;
> + else
> + graph = &small_scale_graph;
> +
> + /* Only need to calibrate the adc values in the linear graph. */
> + graph->adc0 = sc27xx_adc_get_calib_data(calib_data, calib_graph->adc0);
> + graph->adc1 = sc27xx_adc_get_calib_data(calib_data >> 8,
> + calib_graph->adc1);
> +}
> +
> static int sc27xx_adc_get_ratio(int channel, int scale)
> {
> switch (channel) {
> @@ -209,7 +242,7 @@ static void sc27xx_adc_volt_ratio(struct sc27xx_adc_data
> *data,
> *div_denominator = ratio & SC27XX_RATIO_DENOMINATOR_MASK;
> }
>
> -static int sc27xx_adc_to_volt(const struct sc27xx_adc_linear_graph *graph,
> +static int sc27xx_adc_to_volt(struct sc27xx_adc_linear_graph *graph,
> int raw_adc)
> {
> int tmp;
> @@ -371,6 +404,7 @@ static int sc27xx_adc_write_raw(struct iio_dev *indio_dev,
>
> static int sc27xx_adc_enable(struct sc27xx_adc_data *data)
> {
> + u32 val;
> int ret;
>
> ret = regmap_update_bits(data->regmap, SC27XX_MODULE_EN,
> @@ -390,6 +424,18 @@ static int sc27xx_adc_enable(struct sc27xx_adc_data
> *data)
> if (ret)
> goto disable_clk;
>
> + /* ADC channel scales' calibration from nvmem device */
> + ret = nvmem_cell_read_u32(data->dev, "big_scale_calib", &val);
> + if (ret)
> + goto disable_clk;
> +
> + sc27xx_adc_scale_calibration(&big_scale_graph_calib, val, true);
> +
> + ret = nvmem_cell_read_u32(data->dev, "small_scale_calib", &val);
> + if (ret)
> + goto disable_clk;
> +
> + sc27xx_adc_scale_calibration(&small_scale_graph_calib, val, false);
> return 0;
>
> disable_clk:
