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From:   Tingwei Zhang <tingwei@codeaurora.org>
To:     Mathieu Poirier <mathieu.poirier@linaro.org>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Mike Leach <mike.leach@linaro.org>
Cc:     Tingwei Zhang <tingwei@codeaurora.org>, tsoni@codeaurora.org,
        Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>,
        Mao Jinlong <jinlmao@codeaurora.org>,
        coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] coresight: cti: remove pm_runtime_get_sync() from CPU hotplug
Date:   Tue, 18 Aug 2020 19:10:56 +0800
Message-Id: <20200818111057.19755-2-tingwei@codeaurora.org>
In-Reply-To: <20200818111057.19755-1-tingwei@codeaurora.org>
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Below BUG is triggered by call pm_runtime_get_sync() in
cti_cpuhp_enable_hw(). It's in CPU hotplug callback with interrupt
disabled. Pm_runtime_get_sync() calls clock driver to enable clock
which could sleep. Remove pm_runtime_get_sync() in cti_cpuhp_enable_hw()
since pm_runtime_get_sync() is called in cti_enabld and pm_runtime_put()
is called in cti_disabled. No need to increase pm count when CPU gets
online since it's not decreased when CPU is offline.

[  105.800279] BUG: scheduling while atomic: swapper/1/0/0x00000002
[  105.800290] Modules linked in:
[  105.800327] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G        W
5.9.0-rc1-gff1304be0a05-dirty #21
[  105.800337] Hardware name: Thundercomm Dragonboard 845c (DT)
[  105.800353] Call trace:
[  105.800414]  dump_backtrace+0x0/0x1d4
[  105.800439]  show_stack+0x14/0x1c
[  105.800462]  dump_stack+0xc0/0x100
[  105.800490]  __schedule_bug+0x58/0x74
[  105.800523]  __schedule+0x590/0x65c
[  105.800538]  schedule+0x78/0x10c
[  105.800553]  schedule_timeout+0x188/0x250
[  105.800585]  qmp_send.constprop.10+0x12c/0x1b0
[  105.800599]  qmp_qdss_clk_prepare+0x18/0x20
[  105.800622]  clk_core_prepare+0x48/0xd4
[  105.800639]  clk_prepare+0x20/0x34
[  105.800663]  amba_pm_runtime_resume+0x54/0x90
[  105.800695]  __rpm_callback+0xdc/0x138
[  105.800709]  rpm_callback+0x24/0x78
[  105.800724]  rpm_resume+0x328/0x47c
[  105.800739]  __pm_runtime_resume+0x50/0x74
[  105.800768]  cti_starting_cpu+0x40/0xa4
[  105.800795]  cpuhp_invoke_callback+0x84/0x1e0
[  105.800814]  notify_cpu_starting+0x9c/0xb8
[  105.800834]  secondary_start_kernel+0xd8/0x164
[  105.800933] CPU1: Booted secondary processor 0x0000000100 [0x517f803c]

Fixes: e9b880581d55 ("coresight: cti: Add CPU Hotplug handling to CTI driver")
Signed-off-by: Tingwei Zhang <tingwei@codeaurora.org>
---
 drivers/hwtracing/coresight/coresight-cti.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c
index 869569eb8c7f..baba6af83440 100644
--- a/drivers/hwtracing/coresight/coresight-cti.c
+++ b/drivers/hwtracing/coresight/coresight-cti.c
@@ -126,9 +126,7 @@ static int cti_enable_hw(struct cti_drvdata *drvdata)
 static void cti_cpuhp_enable_hw(struct cti_drvdata *drvdata)
 {
 	struct cti_config *config = &drvdata->config;
-	struct device *dev = &drvdata->csdev->dev;
 
-	pm_runtime_get_sync(dev->parent);
 	spin_lock(&drvdata->spinlock);
 	config->hw_powered = true;
 
@@ -148,7 +146,6 @@ static void cti_cpuhp_enable_hw(struct cti_drvdata *drvdata)
 	/* did not re-enable due to no claim / no request */
 cti_hp_not_enabled:
 	spin_unlock(&drvdata->spinlock);
-	pm_runtime_put(dev->parent);
 }
 
 /* disable hardware */
-- 
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