On 06/08/2016 06:53 AM, Yakir Yang wrote:

Marc, Javier

On 06/08/2016 03:44 PM, Marc Zyngier wrote:

quoted

On Wed, 8 Jun 2016 09:28:32 +0800
Yakir Yang [off-list ref] wrote:

quoted

Hi Javier,

On 06/08/2016 01:06 AM, Javier Martinez Canillas wrote:

quoted

Hello Yakir,

On 03/17/2016 05:47 PM, Heiko Stübner wrote:

quoted

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 <redacted>
---

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.

quoted

Once you make this a proper patch, please add my:

Tested-by: Marc Zyngier <redacted>

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

quoted

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