Re: [PATCH v14.1 01/17] drm: bridge: analogix/dp: split exynos dp driver to bridge directory

Javier Martinez Canillas
2016-06-08T14:19:04Z

On 06/08/2016 06:53 AM, Yakir Yang wrote:
> Marc, Javier
>
> On 06/08/2016 03:44 PM, Marc Zyngier wrote:
>> On Wed, 8 Jun 2016 09:28:32 +0800
>> Yakir Yang <ykk@rock-chips.com> wrote:
>>
>>> Hi Javier,
>>>
>>> On 06/08/2016 01:06 AM, Javier Martinez Canillas wrote:
>>>> Hello Yakir,
>>>>
>>>> On 03/17/2016 05:47 PM, Heiko Stübner wrote:
>>>>> Split the dp core driver from exynos directory to bridge directory,
>>>>> and rename the core driver to analogix_dp_*, rename the platform
>>>>> code to exynos_dp.
>>>>>
>>>>> Beside the new analogix_dp driver would export six hooks.
>>>>> "analogix_dp_bind()" and "analogix_dp_unbind()"
>>>>> "analogix_dp_suspned()" and "analogix_dp_resume()"
>>>>> "analogix_dp_detect()" and "analogix_dp_get_modes()"
>>>>>
>>>>> The bind/unbind symbols is used for analogix platform driver to connect
>>>>> with analogix_dp core driver. And the detect/get_modes is used for analogix
>>>>> platform driver to init the connector.
>>>>>
>>>>> They reason why connector need register in helper driver is rockchip drm
>>>>> haven't implement the atomic API, but Exynos drm have implement it, so
>>>>> there would need two different connector helper functions, that's why we
>>>>> leave the connector register in helper driver.
>>>>>
>>>>> Signed-off-by: Yakir Yang <ykk@rock-chips.com>
>>>>> ---
>>>> Marc reported that his Exynos5250 Snow Chromebook fails to boot with v4.7-rc.
>>>>
>>>> I've done a git bisect and tracked down to this commit. The problem is a NULL
>>>> pointer dereference to connector->dev in drm_mode_create(connector->dev) when
>>>> called from exynos_dp_get_modes(). The error log is at [1].
>>>>
>>>> I'm trying to figure out the issue but wanted to mention in case you have any
>>>> hints about what could be the cause. AFAICT the problem is related to the fact
>>>> that drm_connector_init() is called in analogix_dp_bridge_attach() and the
>>>> connector passed as argument is the one in struct analogix_dp_device *dp, but
>>>> later exynos_dp_get_modes() calls drm_mode_create() passing the connector in
>>>> struct exynos_dp_device *dp, which has not been previously initialized.
>>> Agree, this should be the problem, exynos_dp->connector haven't been
>>> initialized, driver should make exynos_dp->dp to a connector point, and
>>> record the passing connector in exynos_dp_bridge_attach(), that should
>>> fix this problem.
>>>
>>>
>>> Thanks,
>>> - Yakir
>>>
>>>
>>> diff --git a/drivers/gpu/drm/exynos/exynos_dp.c
>>> b/drivers/gpu/drm/exynos/exynos_dp.c
>>> index 468498e..4c1fb3f 100644
>>> --- a/drivers/gpu/drm/exynos/exynos_dp.c
>>> +++ b/drivers/gpu/drm/exynos/exynos_dp.c
>>> @@ -34,7 +34,7 @@
>>>
>>> struct exynos_dp_device {
>>> struct drm_encoder encoder;
>>> - struct drm_connector connector;
>>> + struct drm_connector *connector;
>>> struct drm_bridge *ptn_bridge;
>>> struct drm_device *drm_dev;
>>> struct device *dev;
>>> @@ -70,7 +70,7 @@ static int exynos_dp_poweroff(struct
>>> analogix_dp_plat_data *plat_data)
>>> static int exynos_dp_get_modes(struct analogix_dp_plat_data *plat_data)
>>> {
>>> struct exynos_dp_device *dp = to_dp(plat_data);
>>> - struct drm_connector *connector = &dp->connector;
>>> + struct drm_connector *connector = dp->connector;
>>> struct drm_display_mode *mode;
>>> int num_modes = 0;
>>>
>>> @@ -103,6 +103,7 @@ static int exynos_dp_bridge_attach(struct
>>> analogix_dp_plat_data *plat_data,
>>> int ret;
>>>
>>> drm_connector_register(connector);
>>> + dp->connector = connector;
>>>
>>> /* Pre-empt DP connector creation if there's a bridge */
>>> if (dp->ptn_bridge) {
>>>
>> I've just tested this change, and in combination with Javier's DT patch,
>> my Snow is back to its useful state (I'm writing this email from that
>> very Chromebook).
>>

Great. I also tested and the Snow booted but I don't have physical access
to check if the display was brought correctly, So thanks a lot for testing.

>> Once you make this a proper patch, please add my:
>>
>> Tested-by: Marc Zyngier <marc.zyngier@arm.com>
>
> I guess Javier should be the best one to create this patch, if he have no time, i would do it for him. thanks for your report ;)
>

Done.

> - Yakir
>
>> to it.
>>
>> Thanks a lot to you and Javier for tracking this down!
>>

Thanks to you for reporting all the issues!

Best regards,
--
Javier Martinez Canillas
Open Source Group
Samsung Research America