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

[Pavan Kondeti <pavan.kondeti@oss.qualcomm.com>]

On Tue, Oct 28, 2025 at 05:30:48PM +0100, Neil Armstrong wrote:
> On 10/28/25 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
> > `smem` is not present on non qcom devices, we don't make a SMC. In fact
> > we don't even create platform device/driver.
> > 
> > Please help us understand if the better approach is to just register
> > platform driver here and let qcom specific code add the platform device.
> > 
> > Also, please help me understand why would non qcom platform who care
> > about performance load all modules that can be built w/ ARM64. There
> > will be many init calls and platform drivers registerd but they never
> > get probed at all since their platform does not support. I am not
> > defending our aproach, but trying to understand the rationale behind our
> > approach vs alternatives.
> 
> +static int __init gunyah_wdt_init(void)
> 
> will be called on ___all____ arm64 systems which uses the vanilla arm64 defconfig,
> while we could say the first call of "of_find_compatible_node()" would fail on all
> non-qcom platforms this is still unacceptable.
> 

Ok, point taken.

> The solution is to attach the wdt init to something only probed on qcom
> platforms (not the module init, the _probe_ which is mapped to a DT compatible)
> and very generic like socinfo which could accept HYP stuff.
> 
> You could also setup the HYP WDT from the qcom scm driver since the
> communication is smc based.
> 

I think we are trending towards the same approach. Similar to how
`socinfo` platform device is setup by `smem` driver, `gunyah-wdt`
platform device can be added.

Thanks,
Pavan