[PATCH] drm/bridge: analogix dp: Fix runtime PM state in get_modes() callback

[Misha Komarovskiy]

Hello,

On Mon, Nov 27, 2017 at 6:40 AM, Archit Taneja <architt at codeaurora.org> wrote:
>
>
> On 11/21/2017 01:19 PM, Marek Szyprowski wrote:
>>
>> 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.
>
>
> Looks good to me. Would be nice to get an ack from rockchip too. Will queue
> it
> to drm-misc-fixes (so that it's merged for 4.15-rc2) if no one has any
> objections.
>

After this patch accepted to 4.15-rc2 any chances to have it also in
4.14 stable?

I tested it manualy and it fixes boot freeze on snow with 4.14.
If required,
Tested-by: Misha Komarovskiy <zombah at gmail.com>

> Thanks,
> Archit
>
>>
>> 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 at gmail.com>
>> CC: stable at vger.kernel.org # v4.10+
>> Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
>> ---
>> This issue was there from the beginning, but recent changes to DRM
>> core revealed it. It makes sense to backport it to patch f0a8b49c03d2
>> ("drm/bridge: analogix dp: Fix runtime PM state on driver bind"),
>> which fixed similar issue on driver bind, thus I've marked it for
>> stable v4.10+.
>>
>> Best regards
>> Marek Szyprowski
>> Samsung R&D Institute Poland
>> ---
>>   drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
>> b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
>> index 5dd3f1cd074a..a8905049b9da 100644
>> --- 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 drm_connector
>> *connector)
>>                         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);
>>
>
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> a Linux Foundation Collaborative Project



-- 
Best Regards,
Misha Komarovskiy
zombahatgmaildotcom