linux-kernel - Re: [PATCH v3 4/4] watchdog: qcom: add support to read the restart reason from IMEM

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Message-ID: <2036ef2f-c7ef-4f42-858d-8d95c430c21a@oss.qualcomm.com>
Date: Fri, 2 May 2025 16:03:41 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Kathiravan Thirumoorthy <kathiravan.thirumoorthy@....qualcomm.com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck
 <linux@...ck-us.net>, bod.linux@...w.ie
Cc: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-watchdog@...r.kernel.org
Subject: Re: [PATCH v3 4/4] watchdog: qcom: add support to read the restart
 reason from IMEM

On 5/2/25 3:17 PM, 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, XBL update the information in the IMEM region.
> Update the driver to read the restart reason from IMEM and populate the
> bootstatus accordingly.
> 
> With the CONFIG_WATCHDOG_SYSFS enabled, user can extract the information
> as below:
> 
> cat /sys/devices/platform/soc@...410000.watchdog/watchdog/watchdog0/bootstatus
> 32
> 
> 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@....qualcomm.com>
> ---

[...]

> +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->imem_compatible);

Try syscon_regmap_lookup_by_phandle_args() and pass a phandle, see e.g.
drivers/phy/qualcomm/phy-qcom-qmp-pcie.c & phy@...c000 in x1e80100.dtsi

That way all platform specifics will live in the DT, requiring no
hardcode-y driver changes on similar platforms

Konrad