Re: [PATCH v2 3/3] soc: ti: k3-socinfo: Provide reset reason information

[Vignesh Raghavendra <vigneshr@ti.com>]

Hi,

Thanks for the patch!

On 16/03/26 12:34, A. Sverdlin wrote:
> From: Alexander Sverdlin <alexander.sverdlin@siemens.com>
> 
> Add reset_reason attribute decoging the RST_SRC register present in AM64x

s/decoging/decoding . please run spellcheck on commit msg

> and later SoCs of K3 family. Textual representation of the bits was taken
> from the AM62x Processors Technical Reference Manual, except the POR, which
> is not signalled explicitly by the reset module.
> 
> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>


There is support dumping reset reason in U-Boot for AM64x:
https://elixir.bootlin.com/u-boot/v2026.01/source/arch/arm/mach-k3/am64x/boot.c#L107

This conflicts with kernel as U-Boot currently clears the RST_SRC after read (Its
necessary to do so, to detect additional resets at bootloader level). So, this
information would be lost by the time kernel driver comes up.

Is there a usecase where kernel can make use of reset reason information exposed
via this driver? If so, the driver should at least take a cmdline param from 
bootloader in order to overcome above issue.

> ---
> Changelog:
> v2: no changes
> 
>  drivers/soc/ti/k3-socinfo.c | 88 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 88 insertions(+)
> 
> diff --git a/drivers/soc/ti/k3-socinfo.c b/drivers/soc/ti/k3-socinfo.c
> index 676041879eca3..3736c982fd0c8 100644
> --- a/drivers/soc/ti/k3-socinfo.c
> +++ b/drivers/soc/ti/k3-socinfo.c
> @@ -45,6 +45,8 @@
>  #define JTAG_ID_PARTNO_J722S		0xBBA0
>  #define JTAG_ID_PARTNO_AM62LX		0xBBA7
>  
> +#define CTRL_MMR_RST_SRC		8
> +
>  static const struct k3_soc_id {
>  	unsigned int id;
>  	const char *family_name;
> @@ -123,6 +125,90 @@ static const struct regmap_config k3_chipinfo_regmap_cfg = {
>  	.reg_stride = 4,
>  };
>  
> +static u32 k3_reset_source;
> +static const char *const k3_reset_sources[] = {
> +	[0]	= "Reset Caused by MCU Reset Pin",
> +	[1]	= "Power On Reset",			/* Reserved in HW */
> +	[2]	= "Main Reset Pin",
> +	[4]	= "Thermal Reset",
> +	[8]	= "Debug Subsystem Initiated Reset",
> +	[12]	= "SMS Cold Reset",
> +	[13]	= "SMS Warm Reset",
> +	[16]	= "Software Warm Reset",
> +	[20]	= "Software Main Warm Reset From MCU CTRL MMR",
> +	[21]	= "Software Main Warm Reset from MAIN CTRL MMR",
> +	[22]	= "Watchdog Initiated Reset",
> +	[24]	= "Software Main Power On Reset From MCU CTRL MMR",
> +	[25]	= "Software Main Power On Reset From MAIN CTRL MMR",
> +	[30]	= "Reset Caused by Main ESM Error",
> +	[31]	= "Reset Caused by MCU ESM Error",
> +};
> +
> +static ssize_t reset_reason_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	int ret, i;
> +	int total = 0;
> +
> +	for (i = ARRAY_SIZE(k3_reset_sources); i >= 0; i--) {
> +		if (!k3_reset_sources[i] || !(k3_reset_source & BIT(i)))
> +			continue;
> +
> +		ret = sprintf(buf + total, "%s\n", k3_reset_sources[i]);
> +		if (ret < 0)
> +			return ret;
> +		total += ret;
> +		/* Note that several reset sources may be active simultaneously */
> +	}
> +
> +	return total;
> +}
> +
> +static DEVICE_ATTR_RO(reset_reason);
> +
> +static struct attribute *k3_soc_attrs[] = {
> +	&dev_attr_reset_reason.attr,
> +	NULL
> +};
> +
> +ATTRIBUTE_GROUPS(k3_soc);
> +
> +static const struct of_device_id k3_rst_id_table[] = {
> +	{
> +		.compatible	= "ti,am64-rst",
> +	},
> +	{}
> +};
> +
> +static void k3_reset_reason_read(struct soc_device_attribute *soc_dev_attr)
> +{
> +	struct device_node *node = of_find_matching_node(NULL, k3_rst_id_table);
> +	struct regmap *regmap;
> +
> +	/* AM65x/J721E do not have similar registers */
> +	if (!node)
> +		return;
> +
> +	regmap = device_node_to_regmap(node);
> +	of_node_put(node);
> +	if (IS_ERR(regmap)) {
> +		pr_err("Cannot obtain %s regmap\n", k3_rst_id_table[0].compatible);
> +		return;
> +	}
> +
> +	regmap_read(regmap, CTRL_MMR_RST_SRC, &k3_reset_source);
> +	/*
> +	 * The register is only being cleared on POR, so we have to clear reset
> +	 * source of the current boot manually
> +	 */
> +	regmap_write(regmap, CTRL_MMR_RST_SRC, k3_reset_source);
> +
> +	/* Simplify the code a bit and use HW-reserved bit for POR indication */
> +	if (!k3_reset_source)
> +		k3_reset_source |= BIT(1);
> +
> +	soc_dev_attr->custom_attr_group = k3_soc_groups[0];
> +}
> +
>  static int k3_chipinfo_probe(struct platform_device *pdev)
>  {
>  	struct device_node *node = pdev->dev.of_node;
> @@ -183,6 +269,8 @@ static int k3_chipinfo_probe(struct platform_device *pdev)
>  	of_property_read_string(node, "model", &soc_dev_attr->machine);
>  	of_node_put(node);
>  
> +	k3_reset_reason_read(soc_dev_attr);
> +
>  	soc_dev = soc_device_register(soc_dev_attr);
>  	if (IS_ERR(soc_dev)) {
>  		ret = PTR_ERR(soc_dev);

-- 
Regards
Vignesh
https://ti.com/opensource