Re: [PATCH] drm/i915: Init power domains early in driver load

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

On Thu, Jan 07, 2016 at 02:15:50PM +0100, Daniel Vetter wrote:
> On Thu, Jan 7, 2016 at 1:52 PM, Ville Syrj�l�
> <ville.syrjala@linux.intel.com> wrote:
> > On Thu, Jan 07, 2016 at 12:44:21PM +0100, Daniel Vetter wrote:
> >> Since
> >>
> >> commit ac9b8236551d1177fd07b56aef9b565d1864420d
> >> Author: Ville Syrj�l� <ville.syrjala@linux.intel.com>
> >> Date:   Fri Nov 27 18:55:26 2015 +0200
> >>
> >>     drm/i915: Introduce a gmbus power domain
> >>
> >> gmbus also needs the power domain infrastructure right from the start,
> >> since as soon as we register the i2c controllers someone can use them.
> >>
> >> v2: Adjust cleanup paths too (Chris).
> >>
> >> Cc: Ville Syrj�l� <ville.syrjala@linux.intel.com>
> >> Cc: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>
> >> Cc: Imre Deak <imre.deak@intel.com>
> >> Cc: Jani Nikula <jani.nikula@intel.com>
> >> Cc: Meelis Roos <mroos@linux.ee>
> >> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> >> Fixes: ac9b8236551d ("drm/i915: Introduce a gmbus power domain")
> >> Cc: stable@vger.kernel.org
> >> References: http://www.spinics.net/lists/intel-gfx/msg83075.html
> >> Tested-by: Meelis Roos <mroos@linux.ee>
> >> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> >> ---
> >>  drivers/gpu/drm/i915/i915_dma.c | 11 +++++------
> >>  1 file changed, 5 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> >> index 988a3806512a..490d8b0d931e 100644
> >> --- a/drivers/gpu/drm/i915/i915_dma.c
> >> +++ b/drivers/gpu/drm/i915/i915_dma.c
> >> @@ -398,7 +398,6 @@ static int i915_load_modeset_init(struct drm_device *dev)
> >>       if (ret)
> >>               goto cleanup_vga_switcheroo;
> >>
> >> -     intel_power_domains_init_hw(dev_priv, false);
> >>
> >>       intel_csr_ucode_init(dev_priv);
> >>
> >> @@ -1025,6 +1024,8 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
> >>
> >>       intel_irq_init(dev_priv);
> >>       intel_uncore_sanitize(dev);
> >> +     intel_power_domains_init(dev_priv);
> >> +     intel_power_domains_init_hw(dev_priv);
> >
> > I think intel_init_dpio() needs to be moved too. We need to know the
> > DPIO IOSF ports before attempting to talk to the PHY (which can happen
> > from intel_power_domains_init_hw()).
> 
> Ugh, will change.

I think I placed the dpio init in the current place so that it sits next
to intel_device_info_runtime_init(). Doing a lot of hw bashing before
all this runtime device info stuff has been set up seems rather wrong
to me.

> 
> > I'm also wondering why we're doing gmbus init this early. We shouldn't
> > need it until modeset init.
> 
> Anyone can access the gmbus controller once we register it. Userspace
> can (like what seems to happen on Meelis' box), but also the i2c core
> has some auto-probed stuff in some configs afaik.

Sure, but I don't see any reason why we'd need to init it that
early. The only requirement is that we need to init before we ourselves
use it, which I think means we don't actually need it until output setup.
And gmbus being a component of the display engine means the init should
really be part of the modeset init.

So I tend to think the better fix would be to move gmbus init to happen
later.

-- 
Ville Syrj�l�
Intel OTC