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Message-ID: <20190626210042.386ae6e2@archlinux>
Date: Wed, 26 Jun 2019 21:00:42 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Artur Rojek <contact@...ur-rojek.eu>
Cc: Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>, linux-iio@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
Maarten ter Huurne <maarten@...ewalker.org>,
Paul Cercueil <paul@...pouillou.net>
Subject: Re: [PATCH 3/4] IIO: Ingenic JZ47xx: Set clock divider on probe
On Sun, 23 Jun 2019 20:47:31 +0200
Artur Rojek <contact@...ur-rojek.eu> wrote:
> From: Maarten ter Huurne <maarten@...ewalker.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.
>
> Signed-off-by: Maarten ter Huurne <maarten@...ewalker.org>
> Signed-off-by: Artur Rojek <contact@...ur-rojek.eu>
This sounds like it perhaps should be marked as a fix and have appropriate
fixes tag? Otherwise, looks fine to me.
Jonathan
> ---
> 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);
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