Den 11.07.2018 16.06, skrev Maxime Ripard:
CC'ing Noralf and Daniel,

On Wed, Jul 11, 2018 at 09:47:53PM +0800, Icenowy Zheng wrote:
Today, during testing the Banana Pi M2 Zero HDMI patch, I found a
regression on the sun4i-drm driver, which happenes because of the cma
helper change.

The bad commit is 894a677f4b3e6d2ab8d01bb46c1fbd5f92e4591b ("drm/cma-
helper: Use the generic fbdev emulation").

If this commit is present, sun4i_framebuffer_init() will return
-ENODEV, because of the call of drm_client_new(). In this case sun4i-
drv will fail to probe, and all components will be unbound.

By reverting the commit, sun4i-drv loads and HDMI output is correct.

Could anyone investigate into this, please?
Any ideas?

I think it's because drm_fb_cma_fbdev_init() is called before
drm_dev_register() and that this is what returns -ENODEV:

int drm_client_new(struct drm_device *dev, struct drm_client_dev *client,
           const char *name, const struct drm_client_funcs *funcs)
    registered = dev->registered;
    if (registered)
        list_add(&client->list, &dev->clientlist);
    if (!registered) {
        ret = -ENODEV;
        goto err_close;

I would have been nice to get it confirmed that indeed this is the case.

Maybe we should remove this check temporarily until all have converted to
drm_fbdev_generic_setup() which will be called after drm_dev_register().

I'll come back when I have looked at the other drivers to see in which
order they register fbdev and DRM.


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