Re: [PATCH] Revert "drm/i915: Preserve VGACNTR bits from the BIOS"

["Bruno Prémont" <bonbons@linux-vserver.org>]

Hi Ville,

On Tue, 16 Dec 2014 18:38:37 +0200 ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> The VGA_2X_MODE bit apparently affects the display even when the VGA
> plane is disabled. The bit will set by the BIOS when the panel width
> is at least 1280 pixels. So by preserving the bit from the BIOS we
> end up with corrupted display on machines with such high res panels.
> I only have 1024x768 panels on my gen2 machines so never ran into
> this problem.
> 
> The original reason for preserving the VGACNTR register was to make
> my 830 survive S3 with acpi_sleep=s3_bios option. However after
> further 830 fixes that option is no longer needed to make S3 work
> and preserving VGACNTR doesn't seem to be necessary without it,
> so we can just revert the entire patch.
> 
> This reverts commit 69769f9a422bfc62e17399da3590c5e31ac37f24.
>
> Cc: bonbons67@internet.lu

Please swap my old "bugzilla e-mail" address with
  Bruno Prémont <bonbons@linux-vserver.org>

Thanks,
Bruno


> Cc: stable@vger.kernel.org
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=87171
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h      | 2 --
>  drivers/gpu/drm/i915/intel_display.c | 8 +-------
>  2 files changed, 1 insertion(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 16a6f6d..fd2d433 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1665,8 +1665,6 @@ struct drm_i915_private {
>  	 */
>  	struct workqueue_struct *dp_wq;
>  
> -	uint32_t bios_vgacntr;
> -
>  	/* Old dri1 support infrastructure, beware the dragons ya fools entering
>  	 * here! */
>  	struct i915_dri1_state dri1;
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 9cb5c95..cadc3bc 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -12933,11 +12933,7 @@ static void i915_disable_vga(struct drm_device *dev)
>  	vga_put(dev->pdev, VGA_RSRC_LEGACY_IO);
>  	udelay(300);
>  
> -	/*
> -	 * Fujitsu-Siemens Lifebook S6010 (830) has problems resuming
> -	 * from S3 without preserving (some of?) the other bits.
> -	 */
> -	I915_WRITE(vga_reg, dev_priv->bios_vgacntr | VGA_DISP_DISABLE);
> +	I915_WRITE(vga_reg, VGA_DISP_DISABLE);
>  	POSTING_READ(vga_reg);
>  }
>  
> @@ -13026,8 +13022,6 @@ void intel_modeset_init(struct drm_device *dev)
>  
>  	intel_shared_dpll_init(dev);
>  
> -	/* save the BIOS value before clobbering it */
> -	dev_priv->bios_vgacntr = I915_READ(i915_vgacntrl_reg(dev));
>  	/* Just disable it once at startup */
>  	i915_disable_vga(dev);
>  	intel_setup_outputs(dev);