Re: [PATCH] drm/i915: Use the correct GMCH_CTRL register for Sandybridge+

From: Jani Nikula <jani.nikula@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>, intel-gfx@lists.freedesktop.org
Cc: stable@vger.kernel.org
Subject: Re: [PATCH] drm/i915: Use the correct GMCH_CTRL register for Sandybridge+
Date: Tue, 17 Dec 2013 18:03:04 +0200	[thread overview]
Message-ID: <87lhzj1n47.fsf@intel.com> (raw)
In-Reply-To: <1387290890-29786-1-git-send-email-chris@chris-wilson.co.uk>

On Tue, 17 Dec 2013, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> The GMCH_CTRL register (or MGCC in the spec) is at a different address
> on Sandybridge, and the address to which we currently write to is
> undefined. These stray writes appear to upset (hard hang) my Ivybridge
> machine whilst it is in UEFI mode.
>
> Note that the register is still marked as locked RO on Sandybridge, so
> vgaarb is still dysfunctional.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>

> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: stable@vger.kernel.org
> ---
>  drivers/gpu/drm/i915/intel_display.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 7db292c469af..9caf6a879f31 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -11334,9 +11334,10 @@ void intel_connector_attach_encoder(struct intel_connector *connector,
>  int intel_modeset_vga_set_state(struct drm_device *dev, bool state)
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
> +	unsigned reg = INTEL_INFO(dev)->gen >= 6 ? SNB_GMCH_CTRL : INTEL_GMCH_CTRL;
>  	u16 gmch_ctrl;
>  
> -	if (pci_read_config_word(dev_priv->bridge_dev, INTEL_GMCH_CTRL, &gmch_ctrl)) {
> +	if (pci_read_config_word(dev_priv->bridge_dev, reg, &gmch_ctrl)) {
>  		DRM_ERROR("failed to read control word\n");
>  		return -EIO;
>  	}
> @@ -11346,7 +11347,7 @@ int intel_modeset_vga_set_state(struct drm_device *dev, bool state)
>  	else
>  		gmch_ctrl |= INTEL_GMCH_VGA_DISABLE;
>  
> -	if (pci_write_config_word(dev_priv->bridge_dev, INTEL_GMCH_CTRL, gmch_ctrl)) {
> +	if (pci_write_config_word(dev_priv->bridge_dev, reg, gmch_ctrl)) {
>  		DRM_ERROR("failed to write control word\n");
>  		return -EIO;
>  	}
> -- 
> 1.8.5.1
>

-- 
Jani Nikula, Intel Open Source Technology Center
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