Re: [PATCH 4/4] IIO: Ingenic JZ47xx: Add support for JZ4770 SoC ADC.

From: Jonathan Cameron
Date: Wed Jun 26 2019 - 15:59:36 EST

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On Sun, 23 Jun 2019 20:47:32 +0200
Artur Rojek <contact@xxxxxxxxxxxxxx> wrote:

> Add support for the ADC hardware present on Ingenic JZ4770 SoC.
>
> Signed-off-by: Artur Rojek <contact@xxxxxxxxxxxxxx>
> Tested-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
Hi

A few minor comments inline. Main one is that I'd like some numbers
to justify the added complexity in avoiding he uncontended mutex in
the cases where we don't 'need' it. That makes the code more
complex, and I would like to have evidence that it is worth it.

Thanks,

Jonathan

> ---
> drivers/iio/adc/ingenic-adc.c | 134 +++++++++++++++++++++++++++++++---
> 1 file changed, 123 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/iio/adc/ingenic-adc.c b/drivers/iio/adc/ingenic-adc.c
> index e234970b7150..68d1c3280d1a 100644
> --- a/drivers/iio/adc/ingenic-adc.c
> +++ b/drivers/iio/adc/ingenic-adc.c
> @@ -25,9 +25,13 @@
> #define JZ_ADC_REG_ADSDAT 0x20
> #define JZ_ADC_REG_ADCLK 0x28
>
> +#define JZ_ADC_REG_ENABLE_PD BIT(7)
> +#define JZ_ADC_REG_CFG_AUX_MD (BIT(0) | BIT(1))
> #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 JZ4725B_ADC_REG_ADCLK_CLKDIV10US_LSB 16
> +#define JZ4770_ADC_REG_ADCLK_CLKDIV10US_LSB 8
> +#define JZ4770_ADC_REG_ADCLK_CLKDIVMS_LSB 16
>
> #define JZ_ADC_AUX_VREF 3300
> #define JZ_ADC_AUX_VREF_BITS 12
> @@ -37,6 +41,8 @@
> #define JZ4725B_ADC_BATTERY_HIGH_VREF_BITS 10
> #define JZ4740_ADC_BATTERY_HIGH_VREF (7500 * 0.986)
> #define JZ4740_ADC_BATTERY_HIGH_VREF_BITS 12
> +#define JZ4770_ADC_BATTERY_VREF 6600
> +#define JZ4770_ADC_BATTERY_VREF_BITS 12
>
> struct ingenic_adc;
>
> @@ -47,6 +53,8 @@ struct ingenic_adc_soc_data {
> size_t battery_raw_avail_size;
> const int *battery_scale_avail;
> size_t battery_scale_avail_size;
> + unsigned int battery_vref_mode: 1;
> + unsigned int has_aux2: 1;
> int (*init_clk_div)(struct device *dev, struct ingenic_adc *adc);
> };
>
> @@ -54,6 +62,7 @@ struct ingenic_adc {
> void __iomem *base;
> struct clk *clk;
> struct mutex lock;
> + struct mutex aux_lock;
> const struct ingenic_adc_soc_data *soc_data;
> bool low_vref_mode;
> };
> @@ -120,6 +129,8 @@ static int ingenic_adc_write_raw(struct iio_dev *iio_dev,
> case IIO_CHAN_INFO_SCALE:
> switch (chan->channel) {
> case INGENIC_ADC_BATTERY:
> + if (!adc->soc_data->battery_vref_mode)
> + return -EINVAL;
> if (val > JZ_ADC_BATTERY_LOW_VREF) {
> ingenic_adc_set_config(adc,
> JZ_ADC_REG_CFG_BAT_MD,
> @@ -158,6 +169,14 @@ static const int jz4740_adc_battery_scale_avail[] = {
> JZ_ADC_BATTERY_LOW_VREF, JZ_ADC_BATTERY_LOW_VREF_BITS,
> };
>
> +static const int jz4770_adc_battery_raw_avail[] = {
> + 0, 1, (1 << JZ4770_ADC_BATTERY_VREF_BITS) - 1,
> +};
> +
> +static const int jz4770_adc_battery_scale_avail[] = {
> + JZ4770_ADC_BATTERY_VREF, JZ4770_ADC_BATTERY_VREF_BITS,
> +};
> +
> static int jz4725b_adc_init_clk_div(struct device *dev, struct ingenic_adc *adc)
> {
> struct clk *parent_clk;
> @@ -187,7 +206,45 @@ static int jz4725b_adc_init_clk_div(struct device *dev, struct ingenic_adc *adc)
> /* 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) |
> + writel(((div_10us - 1) << JZ4725B_ADC_REG_ADCLK_CLKDIV10US_LSB) |
> + (div_main - 1) << JZ_ADC_REG_ADCLK_CLKDIV_LSB,
> + adc->base + JZ_ADC_REG_ADCLK);
> +
> + return 0;
> +}
> +
> +static int jz4770_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_ms, 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 JZ4770 ADC works at 20 kHz to 200 kHz.
> + * We pick the highest rate possible.
> + */
> + div_main = DIV_ROUND_UP(parent_rate, 200000);
> + div_main = clamp(div_main, 1u, 256u);
> + rate = parent_rate / div_main;
> + if (rate < 20000 || rate > 200000) {
> + 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, 10000);
> + /* And another, which produces a 1ms clock. */
> + div_ms = DIV_ROUND_UP(rate, 1000);
> +
> + writel(((div_ms - 1) << JZ4770_ADC_REG_ADCLK_CLKDIVMS_LSB) |
> + ((div_10us - 1) << JZ4770_ADC_REG_ADCLK_CLKDIV10US_LSB) |
> (div_main - 1) << JZ_ADC_REG_ADCLK_CLKDIV_LSB,
> adc->base + JZ_ADC_REG_ADCLK);
>
> @@ -201,6 +258,8 @@ 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),
> + .battery_vref_mode = true,
> + .has_aux2 = false,
> .init_clk_div = jz4725b_adc_init_clk_div,
> };
>
> @@ -211,9 +270,23 @@ 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),
> + .battery_vref_mode = true,
> + .has_aux2 = false,
> .init_clk_div = NULL, /* no ADCLK register on JZ4740 */
> };
>
> +static const struct ingenic_adc_soc_data jz4770_adc_soc_data = {
> + .battery_high_vref = JZ4770_ADC_BATTERY_VREF,
> + .battery_high_vref_bits = JZ4770_ADC_BATTERY_VREF_BITS,
> + .battery_raw_avail = jz4770_adc_battery_raw_avail,
> + .battery_raw_avail_size = ARRAY_SIZE(jz4770_adc_battery_raw_avail),
> + .battery_scale_avail = jz4770_adc_battery_scale_avail,
> + .battery_scale_avail_size = ARRAY_SIZE(jz4770_adc_battery_scale_avail),
> + .battery_vref_mode = false,
> + .has_aux2 = true,
> + .init_clk_div = jz4770_adc_init_clk_div,
> +};
> +
> static int ingenic_adc_read_avail(struct iio_dev *iio_dev,
> struct iio_chan_spec const *chan,
> const int **vals,
> @@ -246,19 +319,37 @@ static int ingenic_adc_read_raw(struct iio_dev *iio_dev,
> long m)
> {
> struct ingenic_adc *adc = iio_priv(iio_dev);
> - int ret;
> + struct mutex *lock = NULL;

The cost of a lock when not contended should be pretty low.
If we are going to do the optimization of not having the lock for
the single channel case, then I'd like some performance numbers
to justify the complexity. What difference is it making?

> + int bit, ret, engine = 0;
>
> switch (m) {
> case IIO_CHAN_INFO_RAW:
> - clk_enable(adc->clk);
> - ret = ingenic_adc_capture(adc, chan->channel);
> - if (ret) {
> - clk_disable(adc->clk);
> - return ret;
> + switch (chan->channel) {
> + case INGENIC_ADC_AUX:
> + case INGENIC_ADC_AUX2:
> + if (adc->soc_data->has_aux2)
> + lock = &adc->aux_lock;
> + break;
> + case INGENIC_ADC_BATTERY:
> + engine = 1;
> + break;
> }
>
> + if (lock) /* We cannot sample AUX/AUX2 in parallel. */
> + mutex_lock(lock);
> + if (adc->soc_data->has_aux2 && engine == 0) {
> + bit = BIT(chan->channel == INGENIC_ADC_AUX2);
> + ingenic_adc_set_config(adc, JZ_ADC_REG_CFG_AUX_MD, bit);
> + }
> +
> + clk_enable(adc->clk);
> + ret = ingenic_adc_capture(adc, engine);
> + if (ret)
> + goto out;
> +
> switch (chan->channel) {
> case INGENIC_ADC_AUX:
> + case INGENIC_ADC_AUX2:
> *val = readw(adc->base + JZ_ADC_REG_ADSDAT);
> break;
> case INGENIC_ADC_BATTERY:
> @@ -266,12 +357,12 @@ static int ingenic_adc_read_raw(struct iio_dev *iio_dev,
> break;
> }
>
> - clk_disable(adc->clk);
> -
> - return IIO_VAL_INT;
> + ret = IIO_VAL_INT;
> + goto out;
> case IIO_CHAN_INFO_SCALE:
> switch (chan->channel) {
> case INGENIC_ADC_AUX:
> + case INGENIC_ADC_AUX2:
> *val = JZ_ADC_AUX_VREF;
> *val2 = JZ_ADC_AUX_VREF_BITS;
> break;
> @@ -290,6 +381,13 @@ static int ingenic_adc_read_raw(struct iio_dev *iio_dev,
> default:
> return -EINVAL;
> }
> +
> +out:
> + clk_disable(adc->clk);

A bit tricky to follow with this code structure. I'd suggest factoring
out the _RAW block as a utility function so we can avoid the
breaking out of deeply nested code to the handler like this.

> + if (lock)
> + mutex_unlock(lock);
> +
> + return ret;
> }
>
> static void ingenic_adc_clk_cleanup(void *data)
> @@ -322,6 +420,14 @@ static const struct iio_chan_spec ingenic_channels[] = {
> .indexed = 1,
> .channel = INGENIC_ADC_BATTERY,
> },
> + { /* Must always be last in the array. */
> + .extend_name = "aux2",
> + .type = IIO_VOLTAGE,
> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> + BIT(IIO_CHAN_INFO_SCALE),
> + .indexed = 1,
> + .channel = INGENIC_ADC_AUX2,
> + },
> };
>
> static int ingenic_adc_probe(struct platform_device *pdev)
> @@ -343,6 +449,7 @@ static int ingenic_adc_probe(struct platform_device *pdev)
>
> adc = iio_priv(iio_dev);
> mutex_init(&adc->lock);
> + mutex_init(&adc->aux_lock);
> adc->soc_data = soc_data;
>
> mem_base = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> @@ -374,6 +481,7 @@ static int ingenic_adc_probe(struct platform_device *pdev)
> /* Put hardware in a known passive state. */
> writeb(0x00, adc->base + JZ_ADC_REG_ENABLE);
> writeb(0xff, adc->base + JZ_ADC_REG_CTRL);
> + usleep_range(2000, 3000); /* Must wait at least 2ms. */
> clk_disable(adc->clk);
>
> ret = devm_add_action_or_reset(dev, ingenic_adc_clk_cleanup, adc->clk);
> @@ -387,6 +495,9 @@ static int ingenic_adc_probe(struct platform_device *pdev)
> iio_dev->modes = INDIO_DIRECT_MODE;
> iio_dev->channels = ingenic_channels;
> iio_dev->num_channels = ARRAY_SIZE(ingenic_channels);
> + /* Remove AUX2 from the list of supported channels. */
> + if (!adc->soc_data->has_aux2)
> + iio_dev->num_channels -= 1;
> iio_dev->info = &ingenic_adc_info;
>
> ret = devm_iio_device_register(dev, iio_dev);
> @@ -400,6 +511,7 @@ static int ingenic_adc_probe(struct platform_device *pdev)
> static const struct of_device_id ingenic_adc_of_match[] = {
> { .compatible = "ingenic,jz4725b-adc", .data = &jz4725b_adc_soc_data, },
> { .compatible = "ingenic,jz4740-adc", .data = &jz4740_adc_soc_data, },
> + { .compatible = "ingenic,jz4770-adc", .data = &jz4770_adc_soc_data, },
> { },
> };
> MODULE_DEVICE_TABLE(of, ingenic_adc_of_match);

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