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

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Message-ID: <68d280db-f7df-48c8-821d-f7d408c302ad@oss.qualcomm.com>
Date: Fri, 2 May 2025 21:58:56 +0530
From: Kathiravan Thirumoorthy <kathiravan.thirumoorthy@....qualcomm.com>
To: Konrad Dybcio <konrad.dybcio@....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 5/2/2025 7:33 PM, Konrad Dybcio wrote:
>> +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

Thanks. I thought about this API but it didn't strike that I can use the 
args to fetch and match the value.

I need a suggestion here. There is a plan to extend this feature to 
other IPQ targets and also support WDIOF_POWERUNDER and WDIOF_OVERHEAT 
cause as well. For IPQ5424, all 3 cause will support and for other IPQ 
platforms, we are exploring how to integrate WDIOF_OVERHEAT. In any 
case, can I define the DT entry like below

         imem,phandle = <&imem 0x7b0 <Non secure WDT value> <Power Under 
value> <Overheat value>>;

and store these in values args[1], args[2] and args[3] respectively and 
use it for manipulation? If any of the platform doesn't support all 3, I 
can update the bindings and define the number of args as required.

Is this approach fine. Please let me know your comments.

>
> Konrad