[Intel-gfx] [PATCH] drm/i915: Handle changing enable_fbc parameter at runtime better.

[Rodrigo Vivi]

On Tue, Mar 06, 2018 at 11:22:16AM +0100, Maarten Lankhorst wrote:
> Op 05-03-18 om 19:50 schreef Rodrigo Vivi:
> > On Mon, Mar 05, 2018 at 01:36:08PM +0100, Maarten Lankhorst wrote:
> >> If i915.enable_fbc is cleared at runtime, but FBC was previously enabled
> >> then we don't disable FBC until the next time the crtc is disabled.
> >>
> >> Make sure that if the module param is changed, we disable FBC in
> >> intel_fbc_post_update so we never have to worry about disabling.
> > What about switching this from a parameter to debugfs toggle like drrs?
> There are still places where people recommend booting with i915.enable_fbc=0, this would break if we moved it to debugfs.

I think this was exactly what Chris and Joonas were trying to avoid when removing enable_rc6.
To avoid random recommendations of unvalidated combinations.

> 
> Having a small fix is enough.
>

Well... it would be fine for me.

But I went to look the patch and I don't know what exactly we are trying to fix here.

I don't know if it is safe to disable it like this when crtc is already enabled
and mostly: why?! why just not wait until next modeset?

Cc: Paulo

> ~Maarten