Re: [PATCH] drm/i915: force full modeset if the connector is in DPMS OFF mode

[Imre Deak <imre.deak@intel.com>]

On Fri, 2013-05-03 at 13:22 +0100, Chris Wilson wrote:
> On Fri, May 03, 2013 at 02:55:45PM +0300, Imre Deak wrote:
> > On Fri, 2013-05-03 at 12:44 +0100, Chris Wilson wrote:
> > > On Fri, May 03, 2013 at 02:22:09PM +0300, Imre Deak wrote:
> > > > Currently the driver's assumed behavior for a modeset with an attached
> > > > FB is that the corresponding connector will be switched to DPMS ON mode
> > > > if it happened to be in DPMS OFF (or another power save mode). This
> > > > wasn't enforced though if only the FB changed, everything else (format,
> > > > connector etc.) remaining the same. In this case we only set the new FB
> > > > base and left the connector in the old power save mode.
> > > > 
> > > > Fix this by forcing a full modeset whenever there is an attached FB and
> > > > any affected connector is in a power save mode.
> > > > 
> > > > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > > 
> > > NAK. Papering over bugs, much?
> > 
> > Ok. I posted this based on our IRC discussion where we seemed to agree
> > that DPMS_ON is assumed already; just that it's not done consistently.
> > That is if user space does a modeset now that ends up in a full modeset
> > (lets say a new FB with different format) then the kernel will do a
> > DPMS_ON. But if the new FB happens to be the same format then it won't.
> > I thought this is inconsistent and should be fixed.
> > 
> > Another way to make it consistent would be then to remove DPMS ON from
> > the full modeset path..
> 
> Right, we have mentioned in the past that the conflation between DPMS
> and modesetting is a more recent bug that is going to cause us even more
> trouble later. I am not sure how we can fix that as UXA already makes
> many bad assumptions.

Ok, so I assume the right approach for user space is to do an explicit
DPMS_ON after modesetting.

--Imre