Re: [PATCH v2 12/12] watchdog: s3c2410: Add Exynos850 support

[Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>]

On 31/10/2021 13:22, Sam Protsenko wrote:
> Exynos850 is a bit different from SoCs already supported in WDT driver:
>   - AUTOMATIC_WDT_RESET_DISABLE register is removed, so its value is
>     always 0; .disable_auto_reset callback is not set for that reason
>   - MASK_WDT_RESET_REQUEST register is replaced with
>     CLUSTERx_NONCPU_IN_EN register; instead of masking (disabling) WDT
>     reset interrupt it's now enabled with the same value; .mask_reset
>     callback is reused for that functionality though
>   - To make WDT functional, WDT counter needs to be enabled in
>     CLUSTERx_NONCPU_OUT register; it's done using .enable_counter
>     callback
> 
> Also Exynos850 has two CPU clusters, each has its own dedicated WDT
> instance. Different PMU registers and bits are used for each cluster. So
> driver data is now modified in probe, adding needed info depending on
> cluster index passed from device tree.
> 
> Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
> ---
> Changes in v2:
>   - Used single compatible for Exynos850, populating missing driver data in
>     probe
>   - Added "index" property to specify CPU cluster index
> 
>  drivers/watchdog/s3c2410_wdt.c | 68 +++++++++++++++++++++++++++++++++-
>  1 file changed, 66 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c
> index 8fdda2ede1c3..457b725c30ac 100644
> --- a/drivers/watchdog/s3c2410_wdt.c
> +++ b/drivers/watchdog/s3c2410_wdt.c
> @@ -56,6 +56,14 @@
>  #define EXYNOS5_RST_STAT_REG_OFFSET		0x0404
>  #define EXYNOS5_WDT_DISABLE_REG_OFFSET		0x0408
>  #define EXYNOS5_WDT_MASK_RESET_REG_OFFSET	0x040c
> +#define EXYNOS850_CLUSTER0_NONCPU_OUT		0x1220
> +#define EXYNOS850_CLUSTER0_NONCPU_INT_EN	0x1244
> +#define EXYNOS850_CLUSTER1_NONCPU_OUT		0x1620
> +#define EXYNOS850_CLUSTER1_NONCPU_INT_EN	0x1644
> +
> +#define EXYNOS850_CLUSTER0_WDTRESET_BIT		24
> +#define EXYNOS850_CLUSTER1_WDTRESET_BIT		23
> +
>  #define QUIRK_HAS_WTCLRINT_REG			(1 << 0)
>  #define QUIRK_HAS_PMU_MASK_RESET		(1 << 1)
>  #define QUIRK_HAS_PMU_RST_STAT			(1 << 2)
> @@ -171,6 +179,21 @@ static const struct s3c2410_wdt_variant drv_data_exynos7 = {
>  		  QUIRK_HAS_PMU_RST_STAT | QUIRK_HAS_PMU_AUTO_DISABLE,
>  };
>  
> +static const struct s3c2410_wdt_variant drv_data_exynos850 = {
> +	/*
> +	 * Next fields will be set in probe(), based on cluster index:
> +	 *   - .mask_reset_reg
> +	 *   - .rst_stat_bit
> +	 *   - .cnt_en_reg
> +	 */
> +	.mask_reset_inv = true,
> +	.mask_bit = 2,
> +	.rst_stat_reg = EXYNOS5_RST_STAT_REG_OFFSET,
> +	.cnt_en_bit = 7,
> +	.quirks = QUIRK_HAS_WTCLRINT_REG | QUIRK_HAS_PMU_MASK_RESET | \
> +		  QUIRK_HAS_PMU_RST_STAT | QUIRK_HAS_PMU_CNT_EN,
> +};
> +
>  static const struct of_device_id s3c2410_wdt_match[] = {
>  	{ .compatible = "samsung,s3c2410-wdt",
>  	  .data = &drv_data_s3c2410 },
> @@ -182,6 +205,8 @@ static const struct of_device_id s3c2410_wdt_match[] = {
>  	  .data = &drv_data_exynos5420 },
>  	{ .compatible = "samsung,exynos7-wdt",
>  	  .data = &drv_data_exynos7 },
> +	{ .compatible = "samsung,exynos850-wdt",
> +	  .data = &drv_data_exynos850 },
>  	{},
>  };
>  MODULE_DEVICE_TABLE(of, s3c2410_wdt_match);
> @@ -548,15 +573,51 @@ static inline const struct s3c2410_wdt_variant *
>  s3c2410_get_wdt_drv_data(struct platform_device *pdev)
>  {
>  	const struct s3c2410_wdt_variant *variant;
> +	struct s3c2410_wdt_variant *data;
> +	struct device *dev = &pdev->dev;
>  
> -	variant = of_device_get_match_data(&pdev->dev);
> +	variant = of_device_get_match_data(dev);
>  	if (!variant) {
>  		/* Device matched by platform_device_id */
>  		variant = (struct s3c2410_wdt_variant *)
>  			   platform_get_device_id(pdev)->driver_data;
>  	}
>  
> -	return variant;
> +	/* Have to copy driver data over to keep its const qualifier intact */
> +	data = devm_kmemdup(dev, variant, sizeof(*variant), GFP_KERNEL);
> +	if (!data)
> +		return NULL;
> +
> +	/* Populate missing fields for Exynos850 w.r.t. cluster index */
> +	if (variant == &drv_data_exynos850) {
> +		u32 index;
> +		int err;

Another approach is to:
1. Define two variants for Exynos850 (s3c2410_wdt_variants), kind of
like before,
2. if (variant == &drv_data_exynos850)
a. Read the index
b. If index is 0, return first variant,
c. If index is 1, return the second variant,
d. Else - NULL.

This way you won't need to copy the memory on the fly, just use
different const data. Benefits: less memory allocations, entire drvdata
set in one place (so nicely visible), drvdata populated safely via const.

> +
> +		err = of_property_read_u32(dev->of_node, "samsung,index",
> +					   &index);
> +		if (err) {
> +			dev_err(dev, "failed to get cluster index\n");
> +			return NULL;
> +		}
> +
> +		switch (index) {
> +		case 0:
> +			data->mask_reset_reg = EXYNOS850_CLUSTER0_NONCPU_INT_EN;
> +			data->rst_stat_bit = EXYNOS850_CLUSTER0_WDTRESET_BIT;
> +			data->cnt_en_reg = EXYNOS850_CLUSTER0_NONCPU_OUT;
> +			break;
> +		case 1:
> +			data->mask_reset_reg = EXYNOS850_CLUSTER1_NONCPU_INT_EN;
> +			data->rst_stat_bit = EXYNOS850_CLUSTER1_WDTRESET_BIT;
> +			data->cnt_en_reg = EXYNOS850_CLUSTER1_NONCPU_OUT;
> +			break;
> +		default:
> +			dev_err(dev, "wrong cluster index: %u\n", index);
> +			return NULL;
> +		}
> +	}
> +
> +	return data;
>  }
>  
>  static int s3c2410wdt_probe(struct platform_device *pdev)
> @@ -576,6 +637,9 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
>  	wdt->wdt_device = s3c2410_wdd;
>  
>  	wdt->drv_data = s3c2410_get_wdt_drv_data(pdev);
> +	if (!wdt->drv_data)
> +		return -EINVAL;
> +
>  	if (wdt->drv_data->quirks & QUIRKS_HAVE_PMUREG) {
>  		wdt->pmureg = syscon_regmap_lookup_by_phandle(dev->of_node,
>  						"samsung,syscon-phandle");
> 


Best regards,
Krzysztof