linux-kernel - [PATCH v2] s5p-mfc: Don't try to put pm->clock if lookup failed

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Message-Id: <1462216462-32665-1-git-send-email-javier@osg.samsung.com>
Date:	Mon,  2 May 2016 15:14:22 -0400
From:	Javier Martinez Canillas <javier@....samsung.com>
To:	linux-kernel@...r.kernel.org
Cc:	Marek Szyprowski <m.szyprowski@...sung.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Arnd Bergmann <arnd@...db.de>,
	Javier Martinez Canillas <javier@....samsung.com>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Kamil Debski <k.debski@...sung.com>,
	Jeongtae Park <jtp.park@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org
Subject: [PATCH v2] s5p-mfc: Don't try to put pm->clock if lookup failed

Failing to get the struct s5p_mfc_pm .clock is a non-fatal error so the
clock field can have a errno pointer value. But s5p_mfc_final_pm() only
checks if .clock is not NULL before attempting to unprepare and put it.

This leads to the following warning in clk_put() due s5p_mfc_final_pm():

WARNING: CPU: 3 PID: 1023 at drivers/clk/clk.c:2814 s5p_mfc_final_pm+0x48/0x74 [s5p_mfc]
CPU: 3 PID: 1023 Comm: rmmod Tainted: G        W       4.6.0-rc6-next-20160502-00005-g5a15a49106bc #9
Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[<c010e1bc>] (unwind_backtrace) from [<c010af28>] (show_stack+0x10/0x14)
[<c010af28>] (show_stack) from [<c032485c>] (dump_stack+0x88/0x9c)
[<c032485c>] (dump_stack) from [<c011b8e8>] (__warn+0xe8/0x100)
[<c011b8e8>] (__warn) from [<c011b9b0>] (warn_slowpath_null+0x20/0x28)
[<c011b9b0>] (warn_slowpath_null) from [<bf16004c>] (s5p_mfc_final_pm+0x48/0x74 [s5p_mfc])
[<bf16004c>] (s5p_mfc_final_pm [s5p_mfc]) from [<bf157414>] (s5p_mfc_remove+0x8c/0x94 [s5p_mfc])
[<bf157414>] (s5p_mfc_remove [s5p_mfc]) from [<c03fe1f8>] (platform_drv_remove+0x24/0x3c)
[<c03fe1f8>] (platform_drv_remove) from [<c03fcc70>] (__device_release_driver+0x84/0x110)
[<c03fcc70>] (__device_release_driver) from [<c03fcdd8>] (driver_detach+0xac/0xb0)
[<c03fcdd8>] (driver_detach) from [<c03fbff8>] (bus_remove_driver+0x4c/0xa0)
[<c03fbff8>] (bus_remove_driver) from [<c01886a8>] (SyS_delete_module+0x174/0x1b8)
[<c01886a8>] (SyS_delete_module) from [<c01078c0>] (ret_fast_syscall+0x0/0x3c)

Assign the pointer to NULL in case of a lookup failure to fix the issue.

Signed-off-by: Javier Martinez Canillas <javier@....samsung.com>

---

Changes in v2:
- Set the clock pointer to NULL instead of checking for !IS_ERR_OR_NULL().
  Suggested by Arnd Bergmann.

 drivers/media/platform/s5p-mfc/s5p_mfc_pm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/media/platform/s5p-mfc/s5p_mfc_pm.c b/drivers/media/platform/s5p-mfc/s5p_mfc_pm.c
index 5f97a3398c11..9f7522104333 100644
--- a/drivers/media/platform/s5p-mfc/s5p_mfc_pm.c
+++ b/drivers/media/platform/s5p-mfc/s5p_mfc_pm.c
@@ -54,6 +54,7 @@ int s5p_mfc_init_pm(struct s5p_mfc_dev *dev)
 		pm->clock = clk_get(&dev->plat_dev->dev, MFC_SCLK_NAME);
 		if (IS_ERR(pm->clock)) {
 			mfc_info("Failed to get MFC special clock control\n");
+			pm->clock = NULL;
 		} else {
 			clk_set_rate(pm->clock, MFC_SCLK_RATE);
 			ret = clk_prepare_enable(pm->clock);
-- 
2.5.5