Re: [PATCH 5/5] drm/i915: Fix atomic state when reusing the firmware fb

[Matt Roper <matthew.d.roper@intel.com>]

On Thu, Feb 05, 2015 at 05:22:19PM +0000, Damien Lespiau wrote:
> Right now, we get a warning when taking over the firmware fb:
> 
>   [drm:drm_atomic_plane_check] FB set but no CRTC
> 
> with the following backtrace:
> 
>   [<ffffffffa010339d>] drm_atomic_check_only+0x35d/0x510 [drm]
>   [<ffffffffa0103567>] drm_atomic_commit+0x17/0x60 [drm]
>   [<ffffffffa00a6ccd>] drm_atomic_helper_plane_set_property+0x8d/0xd0 [drm_kms_helper]
>   [<ffffffffa00f1fed>] drm_mode_plane_set_obj_prop+0x2d/0x90 [drm]
>   [<ffffffffa00a8a1b>] restore_fbdev_mode+0x6b/0xf0 [drm_kms_helper]
>   [<ffffffffa00aa969>] drm_fb_helper_restore_fbdev_mode_unlocked+0x29/0x80 [drm_kms_helper]
>   [<ffffffffa00aa9e2>] drm_fb_helper_set_par+0x22/0x50 [drm_kms_helper]
>   [<ffffffffa050a71a>] intel_fbdev_set_par+0x1a/0x60 [i915]
>   [<ffffffff813ad444>] fbcon_init+0x4f4/0x580
> 
> That's because we update the plane state with the fb from the firmware, but we
> never associate the plane to that CRTC.
> 
> We don't quite have the full DRM take over from HW state just yet, so
> fake enough of the plane atomic state to pass the checks.
> 
> Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 0d07535..eed1c0c 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -2439,8 +2439,12 @@ intel_find_plane_obj(struct intel_crtc *intel_crtc,
>  		return;
>  
>  	if (intel_alloc_plane_obj(intel_crtc, plane_config)) {
> -		intel_crtc->base.primary->fb = &plane_config->fb->base;
> -		update_state_fb(intel_crtc->base.primary);
> +		struct drm_plane *primary = intel_crtc->base.primary;
> +
> +		primary->fb = &plane_config->fb->base;
> +		primary->state->crtc = &intel_crtc->base;

Would

        drm_atomic_set_crtc_for_plane(primary->state, &intel_crtc->base)

be better here so that the various bitmasks get updated?

> +		update_state_fb(primary);
> +
>  		return;
>  	}
>  
> @@ -2469,6 +2473,7 @@ intel_find_plane_obj(struct intel_crtc *intel_crtc,
>  
>  			drm_framebuffer_reference(c->primary->fb);
>  			intel_crtc->base.primary->fb = c->primary->fb;
> +			c->state->crtc = &intel_crtc->base;

I'm not sure I understand this line.  c->state is the crtc state for the
other CRTC we're going to share with with (and has a backpointer of
c->state->crtc = c).  Was this supposed to be something like

        drm_atomic_set_crtc_for_plane(intel_crtc->base.primary->state,
                                      &intel_crtc->base)

instead?  I'm not sure if updating the other crtc (that we're sharing
with) was a mistake here.


Matt

>  			update_state_fb(intel_crtc->base.primary);
>  			obj->frontbuffer_bits |= INTEL_FRONTBUFFER_PRIMARY(intel_crtc->pipe);
>  			break;
> -- 
> 1.8.3.1
> 

-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795
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