2013/9/12 <ville.syrjala@xxxxxxxxxxxxxxx>: > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > VGA registers live inside the power well on HSW, so in order to write > the VGA MSR register we need the power well to be on. > > We really must write to the register to properly clear the > VGA_MSR_MEM_EN enable bit, even if all VGA registers get zeroed when > the power well is down. It seems that the implicit zeroing done by > the power well is not enough to propagate the VGA_MSR_MEM_EN bit to > whomever is actually responsible for the memory decode ranges. Due to the paragraph above, don't we also need to fix i915_redisable_vga() ? If not, please explain why on the commit message. Don't we also need to do something about i915_enable_vga_mem()? > > If we leave VGA memory decode enabled, and then turn off the power well, > all VGA memory reads will return zeroes. But if we first disable VGA > memory deocde and then turn off the power well, VGA memory reads > return all ones, indicating that the access wasn't claimed by anyone. > For the vga arbiter to function correctly the IGD must not claim the > VGA memory accesses. > > Previously we were doing the VGA_MSR register access while the power well > was excplicitly powered up during driver init. But ever since > > commit 6e1b4fdad5157bb9e88777d525704aba24389bee > Author: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > Date: Thu Sep 5 20:40:52 2013 +0300 > > drm/i915: Delay disabling of VGA memory until vgacon->fbcon handoff is done > > we delay the VGA memory disable until fbcon has initialized, and so > there's a possibility that the power well got turned off during the > fbcon modeset. Also vgacon_save_screen() will need the power well to be > on to be able to read the VGA memory. > > So immediately after enabling the power well during init grab a refence > for VGA purposes, and after all the VGA handling is done, release it. > > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > --- > drivers/gpu/drm/i915/i915_dma.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c > index e5c7b10..23f965d 100644 > --- a/drivers/gpu/drm/i915/i915_dma.c > +++ b/drivers/gpu/drm/i915/i915_dma.c > @@ -1326,6 +1326,9 @@ static int i915_load_modeset_init(struct drm_device *dev) > > intel_init_power_well(dev); > > + /* Keep VGA alive until i915_disable_vga_mem() */ I'd write more here. Maybe copy the paragraph in the commit message. This seems like an important thing and people won't really get the idea if they don't git-blame. > + intel_display_power_get(dev, POWER_DOMAIN_VGA); > + > intel_modeset_gem_init(dev); > > /* Always safe in the mode setting case. */ > @@ -1358,6 +1361,7 @@ static int i915_load_modeset_init(struct drm_device *dev) > * vgacon_save_screen() works during the handover. > */ > i915_disable_vga_mem(dev); > + intel_display_power_put(dev, POWER_DOMAIN_VGA); > > /* Only enable hotplug handling once the fbdev is fully set up. */ > dev_priv->enable_hotplug_processing = true; > -- > 1.8.1.5 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx > http://lists.freedesktop.org/mailman/listinfo/intel-gfx -- Paulo Zanoni _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
