linux-kernel - Re: [PATCH v4 1/2] soc: qcom: smem: Register gunyah watchdog device

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Message-ID: <9421ff80-bd86-4b29-baca-c86da90c91aa@roeck-us.net>
Date: Fri, 31 Oct 2025 08:24:44 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: hrishabh.rajput@....qualcomm.com, Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>,
 Wim Van Sebroeck <wim@...ux-watchdog.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, linux-watchdog@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 Pavan Kondeti <pavan.kondeti@....qualcomm.com>,
 Neil Armstrong <neil.armstrong@...aro.org>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Subject: Re: [PATCH v4 1/2] soc: qcom: smem: Register gunyah watchdog device

On 10/31/25 03:18, Hrishabh Rajput via B4 Relay wrote:
> From: Hrishabh Rajput <hrishabh.rajput@....qualcomm.com>
> 
> To restrict gunyah watchdog initialization to Qualcomm platforms,
> register the watchdog device in the SMEM driver.
> 
> When Gunyah is not present or Gunyah emulates MMIO-based
> watchdog, we expect Qualcomm watchdog or ARM SBSA watchdog device to be
> present in the devicetree. If none of these device nodes are detected,
> we register the SMC-based Gunyah watchdog device.
> 

There should also be an explanation why there is no "qcom,gunyah-wdt"
devicetree node, both here and in the file.

> Signed-off-by: Hrishabh Rajput <hrishabh.rajput@....qualcomm.com>
> ---
>   drivers/soc/qcom/smem.c | 37 +++++++++++++++++++++++++++++++++++++
>   1 file changed, 37 insertions(+)
> 
> diff --git a/drivers/soc/qcom/smem.c b/drivers/soc/qcom/smem.c
> index cf425930539e..40e4749fab02 100644
> --- a/drivers/soc/qcom/smem.c
> +++ b/drivers/soc/qcom/smem.c
> @@ -1118,6 +1118,34 @@ static int qcom_smem_resolve_mem(struct qcom_smem *smem, const char *name,
>   	return 0;
>   }
>   
> +static int register_gunyah_wdt_device(void)
> +{
> +	struct platform_device *gunyah_wdt_dev;
> +	struct device_node *np;
> +
> +	/*
> +	 * When Gunyah is not present or Gunyah is emulating a memory-mapped
> +	 * watchdog, either of Qualcomm watchdog or ARM SBSA watchdog will be
> +	 * present. Skip initialization of SMC-based Gunyah watchdog if that is
> +	 * the case.
> +	 */
> +	np = of_find_compatible_node(NULL, NULL, "qcom,kpss-wdt");
> +	if (np) {
> +		of_node_put(np);
> +		return 0;
> +	}
> +
> +	np = of_find_compatible_node(NULL, NULL, "arm,sbsa-gwdt");
> +	if (np) {
> +		of_node_put(np);
> +		return 0;
> +	}
> +
> +	gunyah_wdt_dev = platform_device_register_simple("gunyah-wdt", -1,
> +							 NULL, 0);
> +	return PTR_ERR_OR_ZERO(gunyah_wdt_dev);
> +}
> +
>   static int qcom_smem_probe(struct platform_device *pdev)
>   {
>   	struct smem_header *header;
> @@ -1236,11 +1264,20 @@ static int qcom_smem_probe(struct platform_device *pdev)
>   	if (IS_ERR(smem->socinfo))
>   		dev_dbg(&pdev->dev, "failed to register socinfo device\n");
>   
> +	ret = register_gunyah_wdt_device();
> +	if (ret)
> +		dev_dbg(&pdev->dev, "failed to register watchdog device\n");
> +
>   	return 0;
>   }
>   
>   static void qcom_smem_remove(struct platform_device *pdev)
>   {
> +	/*
> +	 * Gunyah watchdog is intended to be a persistent module. Hence, the
> +	 * watchdog device is not unregistered.
> +	 */
> +

Odd explanation. I would assume that the smem device is supposed to be
persistent as well. Since  that is not the case, what happens if _this_
device is unregistered and registered again ?

Guenter

>   	platform_device_unregister(__smem->socinfo);
>   
>   	hwspin_lock_free(__smem->hwlock);
>