Re: [PATCH v2 5/5] watchdog: qcom: add support to read the restart reason from IMEM

[Kathiravan Thirumoorthy <kathiravan.thirumoorthy@oss.qualcomm.com>]

On 5/1/2025 5:31 AM, Bryan O'Donoghue wrote:
> On 16/04/2025 09:29, Kathiravan Thirumoorthy wrote:
>> When the system boots up after a watchdog reset, the EXPIRED_STATUS bit
>> in the WDT_STS register is cleared. To identify if the system was restarted
>> due to WDT expiry, bootloaders update the information in the IMEM region.
>> Update the driver to read the restart reason from IMEM and populate the
>> bootstatus accordingly.
> Which bootloaders ?
>
> Do you mean bootrom or one of the subsequent phase bootloaders ?


It is updated by the XBL. I shall mention it explicitly.


>
> Please be specific about which bootloader populates this data i.e. if I
> switch my bootloader to u-boot do I loose the added flag ?
>
>> For backward compatibility, keep the EXPIRED_STATUS bit check. Add a new
>> function qcom_wdt_get_restart_reason() to read the restart reason from
>> IMEM.
>>
>> Signed-off-by: Kathiravan Thirumoorthy <kathiravan.thirumoorthy@oss.qualcomm.com>
> What I'd really love to see here is an example of reading out the data
> from sysfs.
>
> How do I as a user/consumer of this new functionality parse the new data
> it provides ?
>
> Ideally do this in the commit log and recommend doing it in the cover
> letter to, as people don't always read both when commenting on patches.


Sure, will mention the sysfs path and its output in the commit log and 
cover letter.


>
>> ---
>> Changes in v2:
>> 	- Use the syscon API to access the IMEM region
>> 	- Handle the error cases returned by qcom_wdt_get_restart_reason
>> 	- Define device specific data to retrieve the IMEM compatible,
>> 	  offset and the value for non secure WDT, which allows to
>> 	  extend the support for other SoCs
>> ---
>>    drivers/watchdog/qcom-wdt.c | 47 +++++++++++++++++++++++++++++++++++++++++++--
>>    1 file changed, 45 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
>> index 006f9c61aa64fd2b4ee9db493aeb54c8fafac818..94ba9ec9907a19854cd45a94f8da17d6e6eb33bc 100644
>> --- a/drivers/watchdog/qcom-wdt.c
>> +++ b/drivers/watchdog/qcom-wdt.c
>> @@ -7,9 +7,11 @@
>>    #include <linux/interrupt.h>
>>    #include <linux/io.h>
>>    #include <linux/kernel.h>
>> +#include <linux/mfd/syscon.h>
>>    #include <linux/module.h>
>>    #include <linux/of.h>
>>    #include <linux/platform_device.h>
>> +#include <linux/regmap.h>
>>    #include <linux/watchdog.h>
>>
>>    enum wdt_reg {
>> @@ -39,6 +41,9 @@ static const u32 reg_offset_data_kpss[] = {
>>    };
>>
>>    struct qcom_wdt_match_data {
>> +	const char *compatible;
>> +	unsigned int restart_reason_offset;
>> +	unsigned int non_secure_wdt_val;
>>    	const u32 *offset;
>>    	bool pretimeout;
>>    	u32 max_tick_count;
>> @@ -175,6 +180,15 @@ static const struct watchdog_info qcom_wdt_pt_info = {
>>    	.identity	= KBUILD_MODNAME,
>>    };
>>
>> +static const struct qcom_wdt_match_data match_data_ipq5424 = {
>> +	.compatible = "qcom,ipq5424-imem",
>> +	.restart_reason_offset = 0x7b0,
>> +	.non_secure_wdt_val = 0x5,
>> +	.offset = reg_offset_data_kpss,
>> +	.pretimeout = true,
>> +	.max_tick_count = 0xFFFFFU,
>> +};
>> +
> You should separate the addition of your compatibles and their
> descriptor tables from generic functional extensions.
>
> i.e. add the compat string and the above table in a subsequent patch.


Got it. Will split the patch into 2.


>
>>    static const struct qcom_wdt_match_data match_data_apcs_tmr = {
>>    	.offset = reg_offset_data_apcs_tmr,
>>    	.pretimeout = false,
>> @@ -187,6 +201,29 @@ static const struct qcom_wdt_match_data match_data_kpss = {
>>    	.max_tick_count = 0xFFFFFU,
>>    };
>>
>> +static int  qcom_wdt_get_restart_reason(struct qcom_wdt *wdt,
>> +					const struct qcom_wdt_match_data *data)
>> +{
>> +	struct regmap *imem;
>> +	unsigned int val;
>> +	int ret;
>> +
>> +	imem = syscon_regmap_lookup_by_compatible(data->compatible);
>> +	if (IS_ERR(imem))
>> +		return PTR_ERR(imem);
>> +
>> +	ret = regmap_read(imem, data->restart_reason_offset, &val);
>> +	if (ret) {
>> +		dev_err(wdt->wdd.parent, "failed to read the restart reason info\n");
>> +		return ret;
>> +	}
>> +
>> +	if (val == data->non_secure_wdt_val)
>> +		wdt->wdd.bootstatus = WDIOF_CARDRESET;
>> +
>> +	return 0;
>> +}
>> +
>>    static int qcom_wdt_probe(struct platform_device *pdev)
>>    {
>>    	struct device *dev = &pdev->dev;
>> @@ -267,8 +304,13 @@ static int qcom_wdt_probe(struct platform_device *pdev)
>>    	wdt->wdd.parent = dev;
>>    	wdt->layout = data->offset;
>>
>> -	if (readl(wdt_addr(wdt, WDT_STS)) & 1)
>> -		wdt->wdd.bootstatus = WDIOF_CARDRESET;
>> +	ret = qcom_wdt_get_restart_reason(wdt, data);
>> +	if (ret == -ENODEV) {
>> +		if (readl(wdt_addr(wdt, WDT_STS)) & 1)
>> +			wdt->wdd.bootstatus = WDIOF_CARDRESET;
>> +	} else if (ret) {
>> +		return ret;
>> +	}
>>
>>    	/*
>>    	 * If 'timeout-sec' unspecified in devicetree, assume a 30 second
>> @@ -322,6 +364,7 @@ static const struct dev_pm_ops qcom_wdt_pm_ops = {
>>    };
>>
>>    static const struct of_device_id qcom_wdt_of_table[] = {
>> +	{ .compatible = "qcom,apss-wdt-ipq5424", .data = &match_data_ipq5424 },
>>    	{ .compatible = "qcom,kpss-timer", .data = &match_data_apcs_tmr },
>>    	{ .compatible = "qcom,scss-timer", .data = &match_data_apcs_tmr },
>>    	{ .compatible = "qcom,kpss-wdt", .data = &match_data_kpss },
>>
>> --
>> 2.34.1
>>
>>