Re: [PATCH] drm/i915: VGA also requires the power well

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Jun 06, 2013 at 11:35:15AM -0300, Paulo Zanoni wrote:
> 2013/6/6 Ville Syrjälä <ville.syrjala@linux.intel.com>:
> > On Wed, Jun 05, 2013 at 06:05:51PM -0300, Paulo Zanoni wrote:
> >> From: Paulo Zanoni <paulo.r.zanoni@intel.com>
> >>
> >> So add a power domain and check for it before we try to read
> >> VGA_CONTROL.
> >>
> >> This fixes unclaimed register messages that happen on suspend/resume.
> >>
> >> Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
> >> ---
> >>  drivers/gpu/drm/i915/i915_drv.h      | 1 +
> >>  drivers/gpu/drm/i915/intel_display.c | 3 +++
> >>  drivers/gpu/drm/i915/intel_pm.c      | 1 +
> >>  3 files changed, 5 insertions(+)
> >>
> >> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> >> index 46b1f70..d51ce13 100644
> >> --- a/drivers/gpu/drm/i915/i915_drv.h
> >> +++ b/drivers/gpu/drm/i915/i915_drv.h
> >> @@ -89,6 +89,7 @@ enum port {
> >>  #define port_name(p) ((p) + 'A')
> >>
> >>  enum intel_display_power_domain {
> >> +     POWER_DOMAIN_VGA,
> >>       POWER_DOMAIN_PIPE_A,
> >>       POWER_DOMAIN_PIPE_B,
> >>       POWER_DOMAIN_PIPE_C,
> >> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> >> index 4c8fcec..3719d99 100644
> >> --- a/drivers/gpu/drm/i915/intel_display.c
> >> +++ b/drivers/gpu/drm/i915/intel_display.c
> >> @@ -9950,6 +9950,9 @@ void i915_redisable_vga(struct drm_device *dev)
> >>       struct drm_i915_private *dev_priv = dev->dev_private;
> >>       u32 vga_reg = i915_vgacntrl_reg(dev);
> >>
> >> +     if (!intel_display_power_enabled(dev, POWER_DOMAIN_VGA))
> >> +             return;
> >> +
> >
> > So it looks like you're essentially making intel_redisable_vga() a nop
> > for HSW.
> 
> It's not a nop for HSW, it's only a nop if the power well is disabled,
> which means VGA is disabled, so it's a nop if VGA is disabled. But if
> you look at the current function it's also a nop if VGA is disabled.
> So we're keeping the same behavior, but checking the power well before
> checking vga_reg.
> 
> VGA mode requires the power well to be enabled, we can be sure that if
> the power well is disabled, then VGA is disabled, so you don't need to
> do the check for VGA_DISP_DISABLE.

Rigth, but intel_display_power_enabled() only checks the driver power
well register. If BIOS can leave VGA enabled, then I guess it could've
left the power well on too. So I'm thinking we should check for that
rather than the what the driver requested.

-- 
Ville Syrjälä
Intel OTC