[PATCH v4 5/7] thermal: sun8i: add SRAM register access code

[Jernej Škrabec]

Dne petek, 09. februar 2024 ob 15:42:19 CET je Andre Przywara napisal(a):
> The Allwinner H616 SoC needs to clear a bit in one register in the SRAM
> controller, to report reasonable temperature values. On reset, bit 16 in
> register 0x3000000 is set, which leads to the driver reporting
> temperatures around 200C. Clearing this bit brings the values down to the
> expected range. The BSP code does a one-time write in U-Boot, with a
> comment just mentioning the effect on the THS, but offering no further
> explanation.
> 
> To not rely on firmware to set things up for us, add code that queries
> the SRAM controller device via a DT phandle link, then clear just this
> single bit.
> 
> Signed-off-by: Andre Przywara <andre.przywara at arm.com>
> ---
>  drivers/thermal/sun8i_thermal.c | 50 +++++++++++++++++++++++++++++++++
>  1 file changed, 50 insertions(+)
> 
> diff --git a/drivers/thermal/sun8i_thermal.c b/drivers/thermal/sun8i_thermal.c
> index c919b0fd5e169..8a9d2bdc71ece 100644
> --- a/drivers/thermal/sun8i_thermal.c
> +++ b/drivers/thermal/sun8i_thermal.c
> @@ -15,6 +15,7 @@
>  #include <linux/module.h>
>  #include <linux/nvmem-consumer.h>
>  #include <linux/of.h>
> +#include <linux/of_platform.h>
>  #include <linux/platform_device.h>
>  #include <linux/regmap.h>
>  #include <linux/reset.h>
> @@ -66,6 +67,7 @@ struct tsensor {
>  struct ths_thermal_chip {
>  	bool            has_mod_clk;
>  	bool            has_bus_clk_reset;
> +	bool		needs_sram;
>  	int		sensor_num;
>  	int		offset;
>  	int		scale;
> @@ -83,6 +85,7 @@ struct ths_device {
>  	const struct ths_thermal_chip		*chip;
>  	struct device				*dev;
>  	struct regmap				*regmap;
> +	struct regmap_field			*sram_regmap_field;
>  	struct reset_control			*reset;
>  	struct clk				*bus_clk;
>  	struct clk                              *mod_clk;
> @@ -337,6 +340,34 @@ static void sun8i_ths_reset_control_assert(void *data)
>  	reset_control_assert(data);
>  }
>  
> +static struct regmap *sun8i_ths_get_sram_regmap(struct device_node *node)
> +{
> +	struct device_node *sram_node;
> +	struct platform_device *sram_pdev;
> +	struct regmap *regmap = NULL;
> +
> +	sram_node = of_parse_phandle(node, "allwinner,sram", 0);
> +	if (!sram_node)
> +		return ERR_PTR(-ENODEV);
> +
> +	sram_pdev = of_find_device_by_node(sram_node);
> +	if (!sram_pdev) {
> +		/* platform device might not be probed yet */
> +		regmap = ERR_PTR(-EPROBE_DEFER);
> +		goto out_put_node;
> +	}
> +
> +	/* If no regmap is found then the other device driver is at fault */
> +	regmap = dev_get_regmap(&sram_pdev->dev, NULL);
> +	if (!regmap)
> +		regmap = ERR_PTR(-EINVAL);
> +
> +	platform_device_put(sram_pdev);
> +out_put_node:
> +	of_node_put(sram_node);
> +	return regmap;
> +}
> +
>  static int sun8i_ths_resource_init(struct ths_device *tmdev)
>  {
>  	struct device *dev = tmdev->dev;
> @@ -381,6 +412,21 @@ static int sun8i_ths_resource_init(struct ths_device *tmdev)
>  	if (ret)
>  		return ret;
>  
> +	if (tmdev->chip->needs_sram) {
> +		const struct reg_field sun8i_sram_reg_field =
> +			REG_FIELD(0x0, 16, 16);

What about global static constant for a field? Many drivers do so and code 
would be simpler.

Best regards,
Jernej

> +		struct regmap *regmap;
> +
> +		regmap = sun8i_ths_get_sram_regmap(dev->of_node);
> +		if (IS_ERR(regmap))
> +			return PTR_ERR(regmap);
> +		tmdev->sram_regmap_field = devm_regmap_field_alloc(dev,
> +						      regmap,
> +						      sun8i_sram_reg_field);
> +		if (IS_ERR(tmdev->sram_regmap_field))
> +			return PTR_ERR(tmdev->sram_regmap_field);
> +	}
> +
>  	ret = sun8i_ths_calibrate(tmdev);
>  	if (ret)
>  		return ret;
> @@ -427,6 +473,10 @@ static int sun50i_h6_thermal_init(struct ths_device *tmdev)
>  {
>  	int val;
>  
> +	/* The H616 needs to have a bit in the SRAM control register cleared. */
> +	if (tmdev->sram_regmap_field)
> +		regmap_field_write(tmdev->sram_regmap_field, 0);
> +
>  	/*
>  	 * The manual recommends an overall sample frequency of 50 KHz (20us,
>  	 * 480 cycles at 24 MHz), which provides plenty of time for both the
>