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From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Linux PM <linux-pm@vger.kernel.org>
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>, Daniel Lezcano <daniel.lezcano@linaro.org>,
 Laura Nao <laura.nao@collabora.com>
Subject:
 [PATCH v1] thermal: core: Do not fail cdev registration because of invalid
 initial state
Date: Wed, 05 Jun 2024 21:17:17 +0200
Message-ID: <4569763.LvFx2qVVIh@kreacher>
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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 inavlid 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 pass a
negative state value to thermal_debug_cdev_add() instead of failing
if the initial .get_cur_state() callback invocation fails and adjust
the thermal debug code to ignore negative cooling device state values.

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>
Tested-by: Laura Nao <laura.nao@collabora.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/thermal/thermal_core.c    |   11 +++++++----
 drivers/thermal/thermal_debugfs.c |    7 ++++++-
 2 files changed, 13 insertions(+), 5 deletions(-)

Index: linux-pm/drivers/thermal/thermal_core.c
===================================================================
--- linux-pm.orig/drivers/thermal/thermal_core.c
+++ linux-pm/drivers/thermal/thermal_core.c
@@ -964,7 +964,8 @@ __thermal_cooling_device_register(struct
 {
 	struct thermal_cooling_device *cdev;
 	struct thermal_zone_device *pos = NULL;
-	unsigned long current_state;
+	unsigned long val;
+	int current_state;
 	int id, ret;
 
 	if (!ops || !ops->get_max_state || !ops->get_cur_state ||
@@ -1002,9 +1003,11 @@ __thermal_cooling_device_register(struct
 	if (ret)
 		goto out_cdev_type;
 
-	ret = cdev->ops->get_cur_state(cdev, &current_state);
-	if (ret)
-		goto out_cdev_type;
+	ret = cdev->ops->get_cur_state(cdev, &val);
+	if (!ret && val >= 0 && val <= INT_MAX)
+		current_state = val;
+	else
+		current_state = -1;
 
 	thermal_cooling_device_setup_sysfs(cdev);
 
Index: linux-pm/drivers/thermal/thermal_debugfs.c
===================================================================
--- linux-pm.orig/drivers/thermal/thermal_debugfs.c
+++ linux-pm/drivers/thermal/thermal_debugfs.c
@@ -421,6 +421,8 @@ void thermal_debug_cdev_state_update(con
 	cdev_dbg = &thermal_dbg->cdev_dbg;
 
 	old_state = cdev_dbg->current_state;
+	if (old_state < 0)
+		goto unlock;
 
 	/*
 	 * Get the old state information in the durations list. If
@@ -463,6 +465,7 @@ void thermal_debug_cdev_state_update(con
 
 	cdev_dbg->total++;
 
+unlock:
 	mutex_unlock(&thermal_dbg->lock);
 }
 
@@ -499,7 +502,9 @@ void thermal_debug_cdev_add(struct therm
 	 * duration will be printed by cdev_dt_seq_show() as expected if it
 	 * runs before the first state transition.
 	 */
-	thermal_debugfs_cdev_record_get(thermal_dbg, cdev_dbg->durations, state);
+	if (state >= 0)
+		thermal_debugfs_cdev_record_get(thermal_dbg, cdev_dbg->durations,
+						state);
 
 	debugfs_create_file("trans_table", 0400, thermal_dbg->d_top,
 			    thermal_dbg, &tt_fops);