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From:   Dmitry Osipenko <digetx@gmail.com>
To:     Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>
Cc:     linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v1] soc/tegra: pmc: Drop locking from tegra_powergate_is_powered()
Date:   Sun, 21 Oct 2018 21:36:14 +0300
Message-Id: <20181021183614.454-1-digetx@gmail.com>
MIME-Version: 1.0
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Sender: linux-kernel-owner@vger.kernel.org
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This fixes splats like the one below if CONFIG_DEBUG_ATOMIC_SLEEP=y
and machine (Tegra30) booted with SMP=n or all secondary CPU's are put
offline. Locking isn't needed because it protects atomic operation.

# echo 0 | tee /sys/devices/system/cpu/cpu[1-3]/online

BUG: sleeping function called from invalid context at kernel/locking/mutex.c:254
in_atomic(): 1, irqs_disabled(): 128, pid: 0, name: swapper/0
CPU: 0 PID: 0 Comm: swapper/0 Tainted: G         C        4.18.0-next-20180821-00180-gc3ebb6544e44-dirty #823
Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
[<c01134f4>] (unwind_backtrace) from [<c010db2c>] (show_stack+0x20/0x24)
[<c010db2c>] (show_stack) from [<c0bd0f3c>] (dump_stack+0x94/0xa8)
[<c0bd0f3c>] (dump_stack) from [<c0151df8>] (___might_sleep+0x13c/0x174)
[<c0151df8>] (___might_sleep) from [<c0151ea0>] (__might_sleep+0x70/0xa8)
[<c0151ea0>] (__might_sleep) from [<c0bec2b8>] (mutex_lock+0x2c/0x70)
[<c0bec2b8>] (mutex_lock) from [<c0589844>] (tegra_powergate_is_powered+0x44/0xa8)
[<c0589844>] (tegra_powergate_is_powered) from [<c0581a60>] (tegra30_cpu_rail_off_ready+0x30/0x74)
[<c0581a60>] (tegra30_cpu_rail_off_ready) from [<c0122244>] (tegra30_idle_lp2+0xa0/0x108)
[<c0122244>] (tegra30_idle_lp2) from [<c0853438>] (cpuidle_enter_state+0x140/0x540)
[<c0853438>] (cpuidle_enter_state) from [<c08538a4>] (cpuidle_enter+0x40/0x4c)
[<c08538a4>] (cpuidle_enter) from [<c01595e0>] (call_cpuidle+0x30/0x48)
[<c01595e0>] (call_cpuidle) from [<c01599f8>] (do_idle+0x238/0x28c)
[<c01599f8>] (do_idle) from [<c0159d28>] (cpu_startup_entry+0x28/0x2c)
[<c0159d28>] (cpu_startup_entry) from [<c0be76c8>] (rest_init+0xd8/0xdc)
[<c0be76c8>] (rest_init) from [<c1200f50>] (start_kernel+0x41c/0x430)

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/soc/tegra/pmc.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c
index 1fa840e3d930..1714cd818d69 100644
--- a/drivers/soc/tegra/pmc.c
+++ b/drivers/soc/tegra/pmc.c
@@ -543,9 +543,7 @@ int tegra_powergate_is_powered(unsigned int id)
 	if (!tegra_powergate_is_valid(id))
 		return -EINVAL;
 
-	mutex_lock(&pmc->powergates_lock);
 	status = tegra_powergate_state(id);
-	mutex_unlock(&pmc->powergates_lock);
 
 	return status;
 }
-- 
2.19.0