[PATCH 4.9] drm/bridge: analogix dp: Fix runtime PM state on driver bind

[Javier Martinez Canillas]

4.9-stable review patch.

The bug fixed by the commit f0a8b49c03d2 upstream is also needed by 4.9-stable
as reported by kernelci when testing v4.9.17-rc1 [0], and I was also able to
reproduce it with v4.9.18 [1].

I've tested [2] that the mentioned upstream commit fixes the issue.

[0]: https://storage.kernelci.org/stable-rc/v4.9.17-25-g4d90baeca3c8/arm-exynos_defconfig/lab-collabora/boot-exynos5250-snow.html 
[1]: https://lava.collabora.co.uk/scheduler/job/513248/log_file
[2]: https://lava.collabora.co.uk/scheduler/job/513249/log_file

------------------

From: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>

commit f0a8b49c03d22a511a601dc54b2a3425a41e35fa upstream.

Analogix_dp_bind() can be called from component framework, which doesn't
guarantee proper runtime PM state of the device during bind operation,
so ensure that device is runtime active before doing any register access.
This ensures that the power domain, to which DP module belongs, is turned
on. While at it, also fix the unbalanced call to phy_power_on() in
analogix_dp_bind() function.

This patch solves the following kernel oops on Samsung Exynos5250 Snow
board:

Unhandled fault: imprecise external abort (0x406) at 0x00000000
pgd = c0004000
[00000000] *pgd=00000000
Internal error: : 406 [#1] PREEMPT SMP ARM
Modules linked in:
CPU: 0 PID: 75 Comm: kworker/0:2 Not tainted 4.9.0 #1046
Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
Workqueue: events deferred_probe_work_func
task: ee272300 task.stack: ee312000
PC is at analogix_dp_enable_sw_function+0x18/0x2c
LR is at analogix_dp_init_dp+0x2c/0x50
...
[<c03fcb38>] (analogix_dp_enable_sw_function) from [<c03fa9c4>] (analogix_dp_init_dp+0x2c/0x50)
[<c03fa9c4>] (analogix_dp_init_dp) from [<c03fab6c>] (analogix_dp_bind+0x184/0x42c)
[<c03fab6c>] (analogix_dp_bind) from [<c03fdb84>] (component_bind_all+0xf0/0x218)
[<c03fdb84>] (component_bind_all) from [<c03ed64c>] (exynos_drm_load+0x134/0x200)
[<c03ed64c>] (exynos_drm_load) from [<c03d5058>] (drm_dev_register+0xa0/0xd0)
[<c03d5058>] (drm_dev_register) from [<c03d66b8>] (drm_platform_init+0x58/0xb0)
[<c03d66b8>] (drm_platform_init) from [<c03fe0c4>] (try_to_bring_up_master+0x14c/0x188)
[<c03fe0c4>] (try_to_bring_up_master) from [<c03fe188>] (component_add+0x88/0x138)
[<c03fe188>] (component_add) from [<c0403a38>] (platform_drv_probe+0x50/0xb0)
[<c0403a38>] (platform_drv_probe) from [<c0402470>] (driver_probe_device+0x1f0/0x2a8)
[<c0402470>] (driver_probe_device) from [<c0400a54>] (bus_for_each_drv+0x44/0x8c)
[<c0400a54>] (bus_for_each_drv) from [<c04021f8>] (__device_attach+0x9c/0x100)
[<c04021f8>] (__device_attach) from [<c04018e8>] (bus_probe_device+0x84/0x8c)
[<c04018e8>] (bus_probe_device) from [<c0401d1c>] (deferred_probe_work_func+0x60/0x8c)
[<c0401d1c>] (deferred_probe_work_func) from [<c012fc14>] (process_one_work+0x120/0x318)
[<c012fc14>] (process_one_work) from [<c012fe34>] (process_scheduled_works+0x28/0x38)
[<c012fe34>] (process_scheduled_works) from [<c0130048>] (worker_thread+0x204/0x4ac)
[<c0130048>] (worker_thread) from [<c01352c4>] (kthread+0xd8/0xf4)
[<c01352c4>] (kthread) from [<c0107978>] (ret_from_fork+0x14/0x3c)
Code: e59035f0 e5935018 f57ff04f e3c55001 (f57ff04e)
---[ end trace 3d1d0d87796de344 ]---

Reviewed-by: Sean Paul <seanpaul@xxxxxxxxxxxx>
Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Signed-off-by: Archit Taneja <architt@xxxxxxxxxxxxxx>
Link: http://patchwork.freedesktop.org/patch/msgid/1483091866-1088-1-git-send-email-m.szyprowski@xxxxxxxxxxx
---
 drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
index 6e0447f329a2..72ec93de0e76 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -1382,6 +1382,7 @@ int analogix_dp_bind(struct device *dev, struct drm_device *drm_dev,
 
 	pm_runtime_enable(dev);
 
+	pm_runtime_get_sync(dev);
 	phy_power_on(dp->phy);
 
 	analogix_dp_init_dp(dp);
@@ -1414,9 +1415,15 @@ int analogix_dp_bind(struct device *dev, struct drm_device *drm_dev,
 		goto err_disable_pm_runtime;
 	}
 
+	phy_power_off(dp->phy);
+	pm_runtime_put(dev);
+
 	return 0;
 
 err_disable_pm_runtime:
+
+	phy_power_off(dp->phy);
+	pm_runtime_put(dev);
 	pm_runtime_disable(dev);
 
 	return ret;
-- 
2.9.3