linux-kernel - Re: [Intel-gfx] [PATCH v3] i915: Update VGA arbiter support for newer devices

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Date:	Mon, 2 Sep 2013 08:21:44 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:	Alex Williamson <alex.williamson@...hat.com>, airlied@...hat.com,
	intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [Intel-gfx] [PATCH v3] i915: Update VGA arbiter support for
 newer devices

On Fri, Aug 30, 2013 at 03:43:05PM +0300, Ville Syrjälä wrote:
> On Wed, Aug 28, 2013 at 09:39:08AM -0600, Alex Williamson wrote:
> > This is intended to add VGA arbiter support for Intel HD graphics on
> > Core processors.  The old GMCH registers no longer exist, so even
> > though it appears that i915 participates in VGA arbitration, it doesn't
> > work.  On Intel HD graphics we already attempt to disable VGA regions
> > of the device.  This makes registering as a VGA client unnecessary since
> > we don't intend to operate differently depending on how many VGA devices
> > are present.  We can disable VGA memory regions by clearing the memory
> > enable bit in the VGA MSR.  That only leaves VGA IO, which we update
> > the VGA arbiter to know that we don't participate in VGA memory
> > arbitration.  We also add a hook on unload to re-enable memory and
> > reinstate VGA memory arbitration.
> > 
> > Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> 
> Looking good.
> 
> Reviewed-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>

Queued for -next, thanks for the patch.
> 
> > ---
> > 
> > v3: Use explicit LEGACY_IO | LEGACY_MEM when restoring rather than
> >     LEGACY_MASK, per Ville's comments.
> > 
> > v2: I915_READ/WRITE accessors don't work in i915_disable_vga, use inb/outb
> >     directly.  Also, on the driver unbind VGA enable path, acquire legacy
> >     IO to re-enable VGA memory.  Correct comment.

I've added the patch changelog here to the commmit message - I kinda
prefer to keep this bit of information around ...
-Daniel

> > 
> > As with v1, this depends on "vgaarb: Fixes for partial VGA opt-out".  With
> > all patches I'm able to assign a discrete PEG VGA device to a guest and
> > execute the VBIOS w/o interference from IGD or corruption of the IGD
> > framebuffer.
> > 
> >  drivers/gpu/drm/i915/i915_dma.c      |    9 ++++++---
> >  drivers/gpu/drm/i915/intel_display.c |   25 +++++++++++++++++++++++++
> >  2 files changed, 31 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> > index f466980..d9cf216 100644
> > --- a/drivers/gpu/drm/i915/i915_dma.c
> > +++ b/drivers/gpu/drm/i915/i915_dma.c
> > @@ -1287,9 +1287,12 @@ static int i915_load_modeset_init(struct drm_device *dev)
> >  	 * then we do not take part in VGA arbitration and the
> >  	 * vga_client_register() fails with -ENODEV.
> >  	 */
> > -	ret = vga_client_register(dev->pdev, dev, NULL, i915_vga_set_decode);
> > -	if (ret && ret != -ENODEV)
> > -		goto out;
> > +	if (!HAS_PCH_SPLIT(dev)) {
> > +		ret = vga_client_register(dev->pdev, dev, NULL,
> > +					  i915_vga_set_decode);
> > +		if (ret && ret != -ENODEV)
> > +			goto out;
> > +	}
> >  
> >  	intel_register_dsm_handler();
> >  
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index 5fb3058..2807760 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -9519,6 +9519,15 @@ static void i915_disable_vga(struct drm_device *dev)
> >  	outb(SR01, VGA_SR_INDEX);
> >  	sr1 = inb(VGA_SR_DATA);
> >  	outb(sr1 | 1<<5, VGA_SR_DATA);
> > +
> > +	/* Disable VGA memory on Intel HD */
> > +	if (HAS_PCH_SPLIT(dev)) {
> > +		outb(inb(VGA_MSR_READ) & ~VGA_MSR_MEM_EN, VGA_MSR_WRITE);
> > +		vga_set_legacy_decoding(dev->pdev, VGA_RSRC_LEGACY_IO |
> > +						   VGA_RSRC_NORMAL_IO |
> > +						   VGA_RSRC_NORMAL_MEM);
> > +	}
> > +
> >  	vga_put(dev->pdev, VGA_RSRC_LEGACY_IO);
> >  	udelay(300);
> >  
> > @@ -9526,6 +9535,20 @@ static void i915_disable_vga(struct drm_device *dev)
> >  	POSTING_READ(vga_reg);
> >  }
> >  
> > +static void i915_enable_vga(struct drm_device *dev)
> > +{
> > +	/* Enable VGA memory on Intel HD */
> > +	if (HAS_PCH_SPLIT(dev)) {
> > +		vga_get_uninterruptible(dev->pdev, VGA_RSRC_LEGACY_IO);
> > +		outb(inb(VGA_MSR_READ) | VGA_MSR_MEM_EN, VGA_MSR_WRITE);
> > +		vga_set_legacy_decoding(dev->pdev, VGA_RSRC_LEGACY_IO |
> > +						   VGA_RSRC_LEGACY_MEM |
> > +						   VGA_RSRC_NORMAL_IO |
> > +						   VGA_RSRC_NORMAL_MEM);
> > +		vga_put(dev->pdev, VGA_RSRC_LEGACY_IO);
> > +	}
> > +}
> > +
> >  void intel_modeset_init_hw(struct drm_device *dev)
> >  {
> >  	intel_init_power_well(dev);
> > @@ -9983,6 +10006,8 @@ void intel_modeset_cleanup(struct drm_device *dev)
> >  
> >  	intel_disable_fbc(dev);
> >  
> > +	i915_enable_vga(dev);
> > +
> >  	intel_disable_gt_powersave(dev);
> >  
> >  	ironlake_teardown_rc6(dev);
> 
> -- 
> Ville Syrjälä
> Intel OTC
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@...ts.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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