linux-kernel - Re: [PATCH v3] watchdog: Add driver for Gunyah Watchdog

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Message-ID: <jaj5oxqcgckndtp7wwe6ukqbh4z5phe3pw3hnhp2hatgqffjzr@y7qevil4o3yr>
Date: Tue, 28 Oct 2025 18:51:43 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Pavan Kondeti <pavan.kondeti@....qualcomm.com>,
        Hrishabh Rajput <hrishabh.rajput@....qualcomm.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Neil Armstrong <neil.armstrong@...aro.org>
Subject: Re: [PATCH v3] watchdog: Add driver for Gunyah Watchdog

On Tue, Oct 28, 2025 at 05:40:33PM +0100, Krzysztof Kozlowski wrote:
> On 28/10/2025 17:33, Pavan Kondeti wrote:
> > On Tue, Oct 28, 2025 at 05:17:44PM +0100, Krzysztof Kozlowski wrote:
> >> On 28/10/2025 13:27, Pavan Kondeti wrote:
> >>> On Tue, Oct 28, 2025 at 12:07:40PM +0100, Krzysztof Kozlowski wrote:
> >>>> On 28/10/2025 12:04, Krzysztof Kozlowski wrote:
> >>>>> On 28/10/2025 11:58, Hrishabh Rajput wrote:
> >>>>>>
> >>>>>> On 10/28/2025 3:10 PM, Krzysztof Kozlowski wrote:
> >>>>>>> On 28/10/2025 10:35, Hrishabh Rajput via B4 Relay wrote:
> >>>>>>>> +
> >>>>>>>> +static int __init gunyah_wdt_init(void)
> >>>>>>>> +{
> >>>>>>>> +	struct arm_smccc_res res;
> >>>>>>>> +	struct device_node *np;
> >>>>>>>> +	int ret;
> >>>>>>>> +
> >>>>>>>> +	/* Check if we're running on a Qualcomm device */
> >>>>>>>> +	np = of_find_compatible_node(NULL, NULL, "qcom,smem");
> >>>>>>> I don't think you implemented my feedback. This again is executed on
> >>>>>>> every platform, e.g. on Samsung, pointlessly.
> >>>>>>>
> >>>>>>> Implement previous feedback.
> >>>>>>
> >>>>>> Do you want us to add platform device from another driver which is 
> >>>>>> probed only on Qualcomm devices (like socinfo from previous discussion) 
> >>>>>> and get rid of the module init function entirely? As keeping anything in 
> >>>>>> the module init will get it executed on all platforms.
> >>>>>
> >>>>> Instead of asking the same can you read previous discussion? What is
> >>>>> unclear here:
> >>>>> https://lore.kernel.org/all/3b901f9d-dbfa-4f93-a8d2-3e89bd9783c9@kernel.org/
> >>>>> ?
> >>>>>
> >>>>>>
> >>>>>>
> >>>>>> With this patch version, we have tried to reduce the code execution on 
> >>>>>> non-Qualcomm devices (also tried the alternative as mentioned in the 
> >>>>>> cover letter). Adding platform device from another driver as described 
> >>>>>> above would eliminate it entirely, please let us know if you want us to 
> >>>>>> do that.
> >>>>>
> >>>>> Why do I need to repeat the same as last time?
> >>>>
> >>>>
> >>>> Now I see that you completely ignored previous discussion and sent THE
> >>>> SAME approach.
> >>>
> >>> Our intention is not to waste reviewers time at all. It is just a
> >>> misunderstanding on what your comment is about. Let me elaborate further
> >>> not to defend our approach here but to get a clarity so that we don't
> >>> end up in the same situation when v4 is posted.
> >>>
> >>> https://lore.kernel.org/all/b94d8ca3-af58-4a78-9a5a-12e3db0bf75f@kernel.org/ 
> >>>
> >>> You mentioned here
> >>>
> >>> ```
> >>> To me socinfo feels even better. That way only, really only qcom devices
> >>> will execute this SMC.
> >>> ```
> >>>
> >>> We interpreted this comment as `avoid executing this SMC on non qcom
> >>> devices`. That is exactly what we have done in the current patch. since
> >>
> >>
> >> So where did you use socinfo? Point me to the code.
> >>
> > 
> > Okay, lets go a bit deep into the socinfo part. we have used
> > `soc_device_match()` API to detect if the device is qcom (`family =
> > Snapdragon`). It works. However, when we built both `socinfo` and
> 
> socinfo driver. Read my first feedback:
> 
> 
> "No, your hypervisor driver (which you have) should start the module via
> adding platform/aux/something devices."
> 
> And then I agreed if you start it from the socinfo driver.

I'd rather not tie this to socinfo. The socinfo is an optional driver,
which is mainly used to provide debugfs entries. Watchdog is much more
important. It should not be tied to debugfs-only entry.

-- 
With best wishes
Dmitry