Hi Am 05.09.22 um 13:00 schrieb Javier Martinez Canillas:
Hello Thomas, Thanks for your feedback and comments. On 9/5/22 12:41, Thomas Zimmermann wrote:Hi Javier Am 28.08.22 um 17:11 schrieb Javier Martinez Canillas:The simple display pipeline is a set of helpers that can be used by DRM drivers to avoid dealing with all the needed components and just define a few functions to operate a simple display device with one full-screen scanout buffer feeding a single output. But it is arguable that this provides the correct level of abstraction for simple drivers, and recently some have been ported from using these simple display helpers to use the regular atomic helpers instead. The rationale for this is that the simple display pipeline helpers don't hide that much of the DRM complexity, while adding an indirection layer that conflates the concepts of CRTCs and planes. This makes the helpers less flexible and harder to be reused among different graphics drivers. Also, for simple drivers, using the full atomic helpers doesn't require a lot of additional code. So adding a simple display pipeline layer may not be worth it. For these reasons, let's follow that trend and make ssd130x a plain DRM driver that creates its own primary plane, CRTC, enconder and connector.Thanks for considering this change.You are welcome and thanks to you for mentioning this to me. After doing this I'm convinced as well that the simple-KMS / simple display pipeline abstraction doesn't add any value and we should just drop it in favor of the full atomic helpers.Suggested-by: Thomas Zimmermann <tzimmermann@xxxxxxx> Signed-off-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>Acked-by: Thomas Zimmermann <tzimmermann@xxxxxxx>Thanks!There are a few questions below.[...]+static void ssd130x_primary_plane_helper_atomic_update(struct drm_plane *plane, + struct drm_atomic_state *old_state) { - struct ssd130x_device *ssd130x = drm_to_ssd130x(pipe->crtc.dev); + struct drm_plane_state *plane_state = plane->state; + struct drm_plane_state *old_plane_state = drm_atomic_get_old_plane_state(old_state, plane); struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state); - struct drm_device *drm = &ssd130x->drm; - int idx, ret; + struct drm_framebuffer *fb = plane_state->fb; + struct drm_device *drm = plane->dev; + struct drm_rect src_clip, dst_clip; + int idx;- ret = ssd130x_power_on(ssd130x);- if (ret) + if (!fb)I know that some other drivers do this check. But from reading drm_atomic_helper.c, it shouldn't be necesary. If !fb, the plane has been disabled. And because there's an implementation of atomic_disable, the helpers should never call atomic_update on disabled planes. I think the test can be removed.Yes, I just added because noticed that others drivers did. I'll drop it when posting a v2. [...]+static void ssd130x_encoder_helper_atomic_enable(struct drm_encoder *encoder, + struct drm_atomic_state *state) +{ + struct drm_device *drm = encoder->dev; + struct ssd130x_device *ssd130x = drm_to_ssd130x(drm); + int ret; + + ret = ssd130x_power_on(ssd130x); + if (ret) return;- ssd130x_fb_blit_rect(plane_state->fb, &shadow_plane_state->data[0], &dst_clip);+ ret = ssd130x_init(ssd130x); + if (ret) + return ssd130x_power_off(ssd130x);It returns a value from a function returning 'void'?Right. I'll fix it in v2 as well.Is this function the correct place for ssd130x_init() ? It looks a bit heavy for a simple enable operation.Yes, I was abusing the concept of encoder here just to have a place where I could hook the enable / disable logic, since I was looking at the other DRM objects helper operations structures and found that these were only defined for the encoder.
I liked the idea of handling backlighting here. Power on/off also seems sensible.
But there is technically no encoder on this device. As you can see, I was using DRM_MODE_ENCODER_NONE when the encoder is initialized. But I notice now that the struct drm_crtc_helper_funcs also have .enable and .disable callbacks, it seems I was just blind and didn't see before.
You certainly want to use atomic_enable/atomic_disable. They are mutually exclusive with the other enable/disable functions.
Would having the init and poweroff logic in the CRTC helpers be correct to you or was do you have in mind ?
There's quite a bit happening in the init function. Does it have to be re-initialized on each enable operation? If it survives the power-off call, the initial init can be done in the CRTC reset function. It's purpose is to set hardware and software to a clean state.
Best regards Thomas
Best regards Thomas
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev
Attachment:
OpenPGP_signature
Description: OpenPGP digital signature
