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Date:   Thu, 7 Dec 2017 17:32:24 +0200
From:   Ville Syrjälä <ville.syrjala@...ux.intel.com>
To:     Alex Tu <alex.tu@...onical.com>
Cc:     David Airlie <airlied@...ux.ie>, intel-gfx@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Rodrigo Vivi <rodrigo.vivi@...el.com>
Subject: Re: [Intel-gfx] [PATCH] drm/i915: Increase max texture to 16k for
 gen9+

On Thu, Dec 07, 2017 at 05:26:00PM +0800, Alex Tu wrote:
> Rrefer to another patch [1] on mesa to extend width/height to 16384.
> For issue :
>  - https://bugs.freedesktop.org/show_bug.cgi?id=102508
>  - LP: #1714178 Triple monitor display failed with Dell Dock (HiDPI)
> 
> [1] https://patchwork.freedesktop.org/patch/124918/
> 
> Signed-off-by: Alex Tu <alex.tu@...onical.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 47a2f6acee50..556fa57b18b8 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -13905,7 +13905,7 @@ u32 intel_fb_pitch_limit(struct drm_i915_private *dev_priv,
>  		/* "The stride in bytes must not exceed the of the size of 8K
>  		 *  pixels and 32K bytes."

The spec queote clearly says the patch is wrong. Either that or the spec
quote is outdated.

>  		 */
> -		return min(8192 * cpp, 32768);
> +		return min(16384 * cpp, 65536);
>  	} else if (gen >= 5 && !HAS_GMCH_DISPLAY(dev_priv)) {
>  		return 32*1024;
>  	} else if (gen >= 4) {
> @@ -14604,8 +14604,8 @@ int intel_modeset_init(struct drm_device *dev)
>  		dev->mode_config.max_width = 4096;
>  		dev->mode_config.max_height = 4096;
>  	} else {
> -		dev->mode_config.max_width = 8192;
> -		dev->mode_config.max_height = 8192;
> +		dev->mode_config.max_width = 16384;
> +		dev->mode_config.max_height = 16384;

Even if this would be correct (which it's not for most platforms at
least, not quite sure about the very latest hardware), anyone doing
this should at least do a cursory check of the relevant math in the
driver to make seure we don't end up with integer overflows.

>  	}
>  
>  	if (IS_I845G(dev_priv) || IS_I865G(dev_priv)) {
> -- 
> 2.11.0
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel OTC

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