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Message-ID: <a5476bdb-da6f-40d5-baa9-fa2caea72e3d@linaro.org>
Date: Thu, 6 Jun 2024 18:39:02 +0200
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Subject: Re: [PATCH v2] thermal: core: Do not fail cdev registration because
 of invalid initial state
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
 Linux PM <linux-pm@vger.kernel.org>, Laura Nao <laura.nao@collabora.com>
Cc: Linux ACPI <linux-acpi@vger.kernel.org>,
 LKML <linux-kernel@vger.kernel.org>, Lukasz Luba <lukasz.luba@arm.com>,
 Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
 Zhang Rui <rui.zhang@intel.com>
References: <6056838.lOV4Wx5bFT@kreacher>
Content-Language: en-US
From: Daniel Lezcano <daniel.lezcano@linaro.org>
In-Reply-To: <6056838.lOV4Wx5bFT@kreacher>
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On 06/06/2024 18:08, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> It is reported that commit 31a0fa0019b0 ("thermal/debugfs: Pass cooling
> device state to thermal_debug_cdev_add()") causes the ACPI fan driver
> to fail probing on some systems which turns out to be due to the _FST
> control method returning an invalid value until _FSL is first evaluated
> for the given fan.  If this happens, the .get_cur_state() cooling device
> callback returns an error and __thermal_cooling_device_register() fails
> as uses that callback after commit 31a0fa0019b0.
> 
> Arguably, _FST should not return an invalid value even if it is
> evaluated before _FSL, so this may be regarded as a platform firmware
> issue, but at the same time it is not a good enough reason for failing
> the cooling device registration where the initial cooling device state
> is only needed to initialize a thermal debug facility.
> 
> Accordingly, modify __thermal_cooling_device_register() to avoid calling
> thermal_debug_cdev_add() instead of returning an error if the initial
> .get_cur_state() callback invocation fails.
> 
> Fixes: 31a0fa0019b0 ("thermal/debugfs: Pass cooling device state to thermal_debug_cdev_add()")
> Closes: https://lore.kernel.org/linux-acpi/20240530153727.843378-1-laura.nao@collabora.com
> Reported-by: Laura Nao <laura.nao@collabora.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
> 
> v1 -> v2:
>     * Instead of making the thermal debug code effectively ignore the invalid
>       initial cooling device state, simply don't register thermal debugfs for
>       a cooling device if its initial state returned by the driver's
>       .get_cur_state() is invalid (Daniel).
> 
> Laura, please test this one even though I don't see why it wouldn't work for
> you if the v1 did.
> 
> ---
>   drivers/thermal/thermal_core.c |    5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> Index: linux-pm/drivers/thermal/thermal_core.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_core.c
> +++ linux-pm/drivers/thermal/thermal_core.c
> @@ -1001,7 +1001,7 @@ __thermal_cooling_device_register(struct
>   
>   	ret = cdev->ops->get_cur_state(cdev, &current_state);
>   	if (ret)
> -		goto out_cdev_type;
> +		current_state = ULONG_MAX;

Why not move the section ? So we end up below.

>   
>   	thermal_cooling_device_setup_sysfs(cdev);
>   
> @@ -1016,7 +1016,8 @@ __thermal_cooling_device_register(struct
>   		return ERR_PTR(ret);
>   	}
>   
> -	thermal_debug_cdev_add(cdev, current_state);
> +	if (current_state <= cdev->max_state)
> +		thermal_debug_cdev_add(cdev, current_state);

	ret = cdev->ops->get_cur_state(cdev, &current_state);
	if (!ret)
		thermal_debug_cdev_add(cdev, current_state);

Additionally a comment here to explain why get_cur_state can fail and 
telling it is up to the driver to fix its routine?


>   	/* Add 'this' new cdev to the global cdev list */
>   	mutex_lock(&thermal_list_lock);
> 
> 
> 

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