On Thu, Nov 16, 2017 at 1:50 PM, John Stultz john.stultz@linaro.org wrote:
On Wed, Nov 15, 2017 at 4:37 AM, Arnd Bergmann arnd@arndb.de wrote:
An otherwise correct cleanup patch from Dan Carpenter turned a broken failure handling from a feature patch by Hans Verkuil into a kernel Oops, so bisection points to commit 7af35b0addbc ("drm/kirin: Checking for IS_ERR() instead of NULL") rather than 3b1b975003e4 ("drm: adv7511/33: add HDMI CEC support").
I've managed to piece together several partial problems, though I'm still struggling with the bigger picture:
adv7511_probe() registers a drm_bridge structure that was allocated with devm_kzalloc(). It calls adv7511_cec_init(), which fails for an unknown reason, which in turn triggers the registered structure to be removed.
Elsewhere, kirin_drm_platform_probe() gets called, which calls of_graph_get_remote_node(), and that returns NULL. Before Dan's patch we would go on with a NULL pointer here and register that, now kirin_drm_platform_probe() fails with -ENODEV.
In a third driver, dsi_parse_dt() calls drm_of_find_panel_or_bridge(), which after not finding a panel goes on to call of_drm_find_bridge(), and that crashes due to the earlier list corruption.
This addresses the first issue by making sure that adv7511_probe() does not leave behind any corrupted list entries. This should get the system back to boot but needs testing. From my understanding, there is at least one more bug that needs to be resolved to actually get everything to work again.
So I've started hitting the issue this patch tries to address (now that the related code landed in Linus' tree). The only issue is that with this fix, I don't see graphics initializing properly, so I suspect something is still wrong with the error handling (though what exactly I'm not sure).
So this seems to only happen when CONFIG_DRM_I2C_ADV7511_CEC is enabled. If it is on, I don't get any graphics, but if its disabled graphics works.
Tying this with Arnd's patch, I'm guessing adv7511_cec_init() is failing, but it seems like instead of just disabling the CEC feature, we're failing to load the driver entirely.
Maybe should the logic be something like: #ifdef CONFIG_DRM_I2C_ADV7511_CEC ret = adv7511_cec_init(dev, adv7511, offset); if (ret) #endif regmap_write(adv7511->regmap, ADV7511_REG_CEC_CTRL + offset, ADV7511_CEC_CTRL_POWER_DOWN);
? thanks -john