[Intel-gfx] [DRM/I915]: Restore the modeset for every activated CRTC

[yakui]

On Wed, 2009-07-08 at 02:40 +0800, Eric Anholt wrote:
> On Thu, 2009-07-02 at 15:16 +0800, yakui.zhao at intel.com wrote:
> > From: Zhao Yakui <yakui.zhao at intel.com>
> > 
> > Restore the modeset for every activated CRTC in course of resume.
> > This is realized by calling the function of drm_helper_resume_force_mode.
> > Note: it is meaningful only for the KMS mode.
> > 
> > Signed-off-by: Zhao Yakui <yakui.zhao at intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_drv.c |    5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > Index: linux-2.6/drivers/gpu/drm/i915/i915_drv.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/gpu/drm/i915/i915_drv.c	2009-07-02 14:24:44.000000000 +0800
> > +++ linux-2.6/drivers/gpu/drm/i915/i915_drv.c	2009-07-02 14:25:52.000000000 +0800
> > @@ -35,6 +35,7 @@
> >  
> >  #include "drm_pciids.h"
> >  #include <linux/console.h>
> > +#include "drm_crtc_helper.h"
> >  
> >  static unsigned int i915_modeset = -1;
> >  module_param_named(modeset, i915_modeset, int, 0400);
> > @@ -115,6 +116,10 @@
> >  
> >  		drm_irq_install(dev);
> >  	}
> > +	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
> > +		/* Resume the modeset for every activated CRTC */
> > +		drm_helper_resume_force_mode(dev);
> > +	}
> >  
> >  	return ret;
> >  }
> 
> So, this patch does a full modeset on top of the almost-full modeset
> done by the suspend/resume code.  That seems bogus -- if we're going to
> do this, we shouldn't do the rest of the save/restore for mdoesetting.
In course of suspend we will save some registers related with
modesetting. Of course the registers related with interrupt/vga are also
saved.
And in course of resume we will restore the registers.
After doing so, many boxes can work well.
But if the modesetting registers are touched by BIOS in course of
suspend/resume, maybe it is not enough to only restore the registers
related with modesetting. It will be better that we restore the full
modeset for the activated crtc. 
And when the system is resumed from S4, the registers related with
modesetting are not initialized correctly. In such case it will be
better that we restore the modeset.

This patch has no side effect for the box that can work well after using
save/restore. And it can assure that the modeset before entering
suspended state is restored correctly.

If the patch can be shipped, we can remove the register related with
modesetting in save/restore when it works in KMS mode. In fact it
doesn't matter if the we don't remove them. The side effect is that some
registers are restored twice.
> However, note that drm_helper_resume_force_mode doesn't turn off
> disabled connectors, which seems wrong.
the drm_helper_resume_force_mode doesn't touch the disabled connectors.
Why is it necessary to turn off the disabled connectors again?

thanks. 
>