From: Maarten ter Huurne maarten@treewalker.org
The SADC component can run at up to 8 MHz on JZ4725B, but is fed a 12 MHz input clock (EXT). Divide it by two to get 6 MHz, then set up another divider to match, to produce a 10us clock.
If the clock dividers are left on their power-on defaults (a divider of 1), the SADC mostly works, but will occasionally produce erroneous readings. This led to button presses being detected out of nowhere on the RS90 every few minutes. With this change, no ghost button presses were logged in almost a day worth of testing.
The ADCLK register for configuring clock dividers doesn't exist on JZ4740, so avoid writing it there.
A function has been introduced rather than a flag because there is a lot of variation between the ADCLK registers on JZ47xx SoCs, both in the internal layout of the register and in the frequency range supported by the SADC. So this solution should make it easier to add support for other JZ47xx SoCs later.
Fixes: 1a78daea107d ("iio: adc: probe should set clock divider") Signed-off-by: Maarten ter Huurne maarten@treewalker.org Signed-off-by: Artur Rojek contact@artur-rojek.eu ---
Changes:
v2: Add the fixes tag.
drivers/iio/adc/ingenic-adc.c | 54 +++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+)
diff --git a/drivers/iio/adc/ingenic-adc.c b/drivers/iio/adc/ingenic-adc.c index 92b1d5037ac9..e234970b7150 100644 --- a/drivers/iio/adc/ingenic-adc.c +++ b/drivers/iio/adc/ingenic-adc.c @@ -11,6 +11,7 @@ #include <linux/iio/iio.h> #include <linux/io.h> #include <linux/iopoll.h> +#include <linux/kernel.h> #include <linux/module.h> #include <linux/mutex.h> #include <linux/platform_device.h> @@ -22,8 +23,11 @@ #define JZ_ADC_REG_ADTCH 0x18 #define JZ_ADC_REG_ADBDAT 0x1c #define JZ_ADC_REG_ADSDAT 0x20 +#define JZ_ADC_REG_ADCLK 0x28
#define JZ_ADC_REG_CFG_BAT_MD BIT(4) +#define JZ_ADC_REG_ADCLK_CLKDIV_LSB 0 +#define JZ_ADC_REG_ADCLK_CLKDIV10US_LSB 16
#define JZ_ADC_AUX_VREF 3300 #define JZ_ADC_AUX_VREF_BITS 12 @@ -34,6 +38,8 @@ #define JZ4740_ADC_BATTERY_HIGH_VREF (7500 * 0.986) #define JZ4740_ADC_BATTERY_HIGH_VREF_BITS 12
+struct ingenic_adc; + struct ingenic_adc_soc_data { unsigned int battery_high_vref; unsigned int battery_high_vref_bits; @@ -41,6 +47,7 @@ struct ingenic_adc_soc_data { size_t battery_raw_avail_size; const int *battery_scale_avail; size_t battery_scale_avail_size; + int (*init_clk_div)(struct device *dev, struct ingenic_adc *adc); };
struct ingenic_adc { @@ -151,6 +158,42 @@ static const int jz4740_adc_battery_scale_avail[] = { JZ_ADC_BATTERY_LOW_VREF, JZ_ADC_BATTERY_LOW_VREF_BITS, };
+static int jz4725b_adc_init_clk_div(struct device *dev, struct ingenic_adc *adc) +{ + struct clk *parent_clk; + unsigned long parent_rate, rate; + unsigned int div_main, div_10us; + + parent_clk = clk_get_parent(adc->clk); + if (!parent_clk) { + dev_err(dev, "ADC clock has no parent\n"); + return -ENODEV; + } + parent_rate = clk_get_rate(parent_clk); + + /* + * The JZ4725B ADC works at 500 kHz to 8 MHz. + * We pick the highest rate possible. + * In practice we typically get 6 MHz, half of the 12 MHz EXT clock. + */ + div_main = DIV_ROUND_UP(parent_rate, 8000000); + div_main = clamp(div_main, 1u, 64u); + rate = parent_rate / div_main; + if (rate < 500000 || rate > 8000000) { + dev_err(dev, "No valid divider for ADC main clock\n"); + return -EINVAL; + } + + /* We also need a divider that produces a 10us clock. */ + div_10us = DIV_ROUND_UP(rate, 100000); + + writel(((div_10us - 1) << JZ_ADC_REG_ADCLK_CLKDIV10US_LSB) | + (div_main - 1) << JZ_ADC_REG_ADCLK_CLKDIV_LSB, + adc->base + JZ_ADC_REG_ADCLK); + + return 0; +} + static const struct ingenic_adc_soc_data jz4725b_adc_soc_data = { .battery_high_vref = JZ4725B_ADC_BATTERY_HIGH_VREF, .battery_high_vref_bits = JZ4725B_ADC_BATTERY_HIGH_VREF_BITS, @@ -158,6 +201,7 @@ static const struct ingenic_adc_soc_data jz4725b_adc_soc_data = { .battery_raw_avail_size = ARRAY_SIZE(jz4725b_adc_battery_raw_avail), .battery_scale_avail = jz4725b_adc_battery_scale_avail, .battery_scale_avail_size = ARRAY_SIZE(jz4725b_adc_battery_scale_avail), + .init_clk_div = jz4725b_adc_init_clk_div, };
static const struct ingenic_adc_soc_data jz4740_adc_soc_data = { @@ -167,6 +211,7 @@ static const struct ingenic_adc_soc_data jz4740_adc_soc_data = { .battery_raw_avail_size = ARRAY_SIZE(jz4740_adc_battery_raw_avail), .battery_scale_avail = jz4740_adc_battery_scale_avail, .battery_scale_avail_size = ARRAY_SIZE(jz4740_adc_battery_scale_avail), + .init_clk_div = NULL, /* no ADCLK register on JZ4740 */ };
static int ingenic_adc_read_avail(struct iio_dev *iio_dev, @@ -317,6 +362,15 @@ static int ingenic_adc_probe(struct platform_device *pdev) return ret; }
+ /* Set clock dividers. */ + if (soc_data->init_clk_div) { + ret = soc_data->init_clk_div(dev, adc); + if (ret) { + clk_disable_unprepare(adc->clk); + return ret; + } + } + /* Put hardware in a known passive state. */ writeb(0x00, adc->base + JZ_ADC_REG_ENABLE); writeb(0xff, adc->base + JZ_ADC_REG_CTRL);