4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> commit 510353a63796d467b41237ab4f136136f68c297d upstream. get_modes() callback might be called asynchronously from the DRM core and it is not synchronized with bridge_enable(), which sets proper runtime PM state of the main DP device. Fix this by calling pm_runtime_get_sync() before calling drm_get_edid(), which in turn calls drm_dp_i2c_xfer() and analogix_dp_transfer() to ensure that main DP device is runtime active when doing any access to its registers. This fixes the following kernel issue 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: 62 Comm: kworker/0:2 Not tainted 4.13.0-rc2-00364-g4a97a3da420b #3357 Hardware name: SAMSUNG EXYNOS (Flattened Device Tree) Workqueue: events output_poll_execute task: edc14800 task.stack: edcb2000 PC is at analogix_dp_transfer+0x15c/0x2fc LR is at analogix_dp_transfer+0x134/0x2fc pc : [<c0468538>] lr : [<c0468510>] psr: 60000013 sp : edcb3be8 ip : 0000002a fp : 00000001 r10: 00000000 r9 : edcb3cd8 r8 : edcb3c40 r7 : 00000000 r6 : edd3b380 r5 : edd3b010 r4 : 00000064 r3 : 00000000 r2 : f0ad3000 r1 : edcb3c40 r0 : edd3b010 Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none Control: 10c5387d Table: 4000406a DAC: 00000051 Process kworker/0:2 (pid: 62, stack limit = 0xedcb2210) Stack: (0xedcb3be8 to 0xedcb4000) [<c0468538>] (analogix_dp_transfer) from [<c0424ba4>] (drm_dp_i2c_do_msg+0x8c/0x2b4) [<c0424ba4>] (drm_dp_i2c_do_msg) from [<c0424e64>] (drm_dp_i2c_xfer+0x98/0x214) [<c0424e64>] (drm_dp_i2c_xfer) from [<c057b2d8>] (__i2c_transfer+0x140/0x29c) [<c057b2d8>] (__i2c_transfer) from [<c057b4a4>] (i2c_transfer+0x70/0xe4) [<c057b4a4>] (i2c_transfer) from [<c0441de4>] (drm_do_probe_ddc_edid+0xb4/0x114) [<c0441de4>] (drm_do_probe_ddc_edid) from [<c0441e5c>] (drm_probe_ddc+0x18/0x28) [<c0441e5c>] (drm_probe_ddc) from [<c0445728>] (drm_get_edid+0x124/0x2d4) [<c0445728>] (drm_get_edid) from [<c0465ea0>] (analogix_dp_get_modes+0x90/0x114) [<c0465ea0>] (analogix_dp_get_modes) from [<c0425e8c>] (drm_helper_probe_single_connector_modes+0x198/0x68c) [<c0425e8c>] (drm_helper_probe_single_connector_modes) from [<c04325d4>] (drm_setup_crtcs+0x1b4/0xd18) [<c04325d4>] (drm_setup_crtcs) from [<c04344a8>] (drm_fb_helper_hotplug_event+0x94/0xd0) [<c04344a8>] (drm_fb_helper_hotplug_event) from [<c0425a50>] (drm_kms_helper_hotplug_event+0x24/0x28) [<c0425a50>] (drm_kms_helper_hotplug_event) from [<c04263ec>] (output_poll_execute+0x6c/0x174) [<c04263ec>] (output_poll_execute) from [<c0136f18>] (process_one_work+0x188/0x3fc) [<c0136f18>] (process_one_work) from [<c01371f4>] (worker_thread+0x30/0x4b8) [<c01371f4>] (worker_thread) from [<c013daf8>] (kthread+0x128/0x164) [<c013daf8>] (kthread) from [<c0108510>] (ret_from_fork+0x14/0x24) Code: 0a000002 ea000009 e2544001 0a00004a (e59537c8) ---[ end trace cddc7919c79f7878 ]--- Reported-by: Misha Komarovskiy <zombah@xxxxxxxxx> Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Archit Taneja <architt@xxxxxxxxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20171121074936.22520-1-m.szyprowski@xxxxxxxxxxx --- drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 2 ++ 1 file changed, 2 insertions(+) --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c @@ -946,7 +946,9 @@ static int analogix_dp_get_modes(struct return 0; } + pm_runtime_get_sync(dp->dev); edid = drm_get_edid(connector, &dp->aux.ddc); + pm_runtime_put(dp->dev); if (edid) { drm_mode_connector_update_edid_property(&dp->connector, edid);