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 <[email protected]> --- Changes from v1: - Use nvmem_cell_read() instead of nvmem_cell_read_u32(). --- .../bindings/iio/adc/sprd,sc27xx-adc.txt | 4 ++ drivers/iio/adc/sc27xx_adc.c | 74 +++++++++++++++++++- 2 files changed, 75 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..7940b23 100644 --- a/drivers/iio/adc/sc27xx_adc.c +++ b/drivers/iio/adc/sc27xx_adc.c @@ -5,10 +5,12 @@ #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> #include <linux/regmap.h> +#include <linux/slab.h> /* PMIC global registers definition */ #define SC27XX_MODULE_EN 0xc08 @@ -87,16 +89,73 @@ 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 int sc27xx_adc_scale_calibration(struct sc27xx_adc_data *data, + bool big_scale) +{ + const struct sc27xx_adc_linear_graph *calib_graph; + struct sc27xx_adc_linear_graph *graph; + struct nvmem_cell *cell; + const char *cell_name; + u32 calib_data = 0; + void *buf; + size_t len; + + if (big_scale) { + calib_graph = &big_scale_graph_calib; + graph = &big_scale_graph; + cell_name = "big_scale_calib"; + } else { + calib_graph = &small_scale_graph_calib; + graph = &small_scale_graph; + cell_name = "small_scale_calib"; + } + + cell = nvmem_cell_get(data->dev, cell_name); + if (IS_ERR(cell)) + return PTR_ERR(cell); + + buf = nvmem_cell_read(cell, &len); + nvmem_cell_put(cell); + + if (IS_ERR(buf)) + return PTR_ERR(buf); + + memcpy(&calib_data, buf, min(len, sizeof(u32))); + + /* 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); + + kfree(buf); + return 0; +} + static int sc27xx_adc_get_ratio(int channel, int scale) { switch (channel) { @@ -209,7 +268,7 @@ 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; @@ -390,6 +449,15 @@ static int sc27xx_adc_enable(struct sc27xx_adc_data *data) if (ret) goto disable_clk; + /* ADC channel scales' calibration from nvmem device */ + ret = sc27xx_adc_scale_calibration(data, true); + if (ret) + goto disable_clk; + + ret = sc27xx_adc_scale_calibration(data, false); + if (ret) + goto disable_clk; + return 0; disable_clk: -- 1.7.9.5
