Hi Samuel,

On Tue, Sep 07, 2021 at 10:40:15PM -0500, Samuel Holland wrote:
> Until the R329, the LRADC hardware was always active. Now it requires
> enabling a clock gate and deasserting a reset line. Do this if the clock
> and reset are provided in the device tree, but keep them optional to
> maintain support for the existing binding.
> 
> Signed-off-by: Samuel Holland <samuel@sholland.org>
> ---
>  drivers/input/keyboard/sun4i-lradc-keys.c | 29 +++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/drivers/input/keyboard/sun4i-lradc-keys.c b/drivers/input/keyboard/sun4i-lradc-keys.c
> index 4a796bed48ac..50fc18052829 100644
> --- a/drivers/input/keyboard/sun4i-lradc-keys.c
> +++ b/drivers/input/keyboard/sun4i-lradc-keys.c
> @@ -14,6 +14,7 @@
>   * there are no boards known to use channel 1.
>   */
>  
> +#include <linux/clk.h>
>  #include <linux/err.h>
>  #include <linux/init.h>
>  #include <linux/input.h>
> @@ -23,6 +24,7 @@
>  #include <linux/of_platform.h>
>  #include <linux/platform_device.h>
>  #include <linux/regulator/consumer.h>
> +#include <linux/reset.h>
>  #include <linux/slab.h>
>  
>  #define LRADC_CTRL		0x00
> @@ -83,6 +85,8 @@ struct sun4i_lradc_data {
>  	struct device *dev;
>  	struct input_dev *input;
>  	void __iomem *base;
> +	struct clk *clk;
> +	struct reset_control *reset;
>  	struct regulator *vref_supply;
>  	struct sun4i_lradc_keymap *chan0_map;
>  	const struct lradc_variant *variant;
> @@ -140,6 +144,14 @@ static int sun4i_lradc_open(struct input_dev *dev)
>  	if (error)
>  		return error;
>  
> +	error = reset_control_deassert(lradc->reset);
> +	if (error)
> +		goto err_disable_reg;
> +
> +	error = clk_prepare_enable(lradc->clk);
> +	if (error)
> +		goto err_assert_reset;
> +
>  	lradc->vref = regulator_get_voltage(lradc->vref_supply) *
>  		      lradc->variant->divisor_numerator /
>  		      lradc->variant->divisor_denominator;
> @@ -153,6 +165,13 @@ static int sun4i_lradc_open(struct input_dev *dev)
>  	writel(CHAN0_KEYUP_IRQ | CHAN0_KEYDOWN_IRQ, lradc->base + LRADC_INTC);
>  
>  	return 0;
> +
> +err_assert_reset:
> +	reset_control_assert(lradc->reset);
> +err_disable_reg:
> +	regulator_disable(lradc->vref_supply);
> +
> +	return error;
>  }
>  
>  static void sun4i_lradc_close(struct input_dev *dev)
> @@ -164,6 +183,8 @@ static void sun4i_lradc_close(struct input_dev *dev)
>  		SAMPLE_RATE(2), lradc->base + LRADC_CTRL);
>  	writel(0, lradc->base + LRADC_INTC);
>  
> +	clk_disable_unprepare(lradc->clk);
> +	reset_control_assert(lradc->reset);
>  	regulator_disable(lradc->vref_supply);
>  }
>  
> @@ -243,6 +264,14 @@ static int sun4i_lradc_probe(struct platform_device *pdev)
>  		return -EINVAL;
>  	}
>  
> +	lradc->clk = devm_clk_get_optional(dev, NULL);
> +	if (IS_ERR(lradc->clk))
> +		return PTR_ERR(lradc->clk);
> +
> +	lradc->reset = devm_reset_control_get_optional_exclusive(dev, NULL);
> +	if (IS_ERR(lradc->reset))
> +		return PTR_ERR(lradc->reset);
> +

This wouldn't report an error if the clocks are missing on the R329 (and
D1), even though they are required. The way we usually deal with this is
through a flag in the variant structure (at least to guard clk_get /
reset_control_get)

Maxime