[PATCH] drm/i915: fix corruptions on i8xx due to relaxed fencing

[Indan Zupancic]

Hi,

On Tue, February 22, 2011 18:25, Daniel Vetter wrote:
> It looks like gen2 has a peculiar interleaved 2-row inter-tile
> layout. Probably inherited from i81x which had 2kb tiles (which
> naturally fit an even-number-of-tile-rows scheme to fit onto 4kb
> pages). There is no other mention of this in any docs (also not
> in the Intel internal documention according to Chris Wilson).
>
> Problem manifests itself in corruptions in the second half of the
> last tile row (if the bo has an odd number of tiles). Which can
> only happen with relaxed tiling (introduced in a00b10c360b35d6431a9).
>
> So reject set_tiling calls that don't satisfy this constrain to
> prevent broken userspace from causing havoc. While at it, also
> check the size for newer chipsets.
>
> LKML: https://lkml.org/lkml/2011/2/19/5
> Reported-by: Indan Zupancic <indan at nul.nu>
> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> ---
>  drivers/gpu/drm/i915/i915_gem_tiling.c |   16 +++++++++++++++-
>  1 files changed, 15 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_tiling.c
> b/drivers/gpu/drm/i915/i915_gem_tiling.c
> index 22a32b9..79a04fd 100644
> --- a/drivers/gpu/drm/i915/i915_gem_tiling.c
> +++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
> @@ -184,7 +184,7 @@ i915_gem_detect_bit_6_swizzle(struct drm_device *dev)
>  static bool
>  i915_tiling_ok(struct drm_device *dev, int stride, int size, int tiling_mode)
>  {
> -	int tile_width;
> +	int tile_width, tile_height;
>
>  	/* Linear is always fine */
>  	if (tiling_mode == I915_TILING_NONE)
> @@ -215,6 +215,20 @@ i915_tiling_ok(struct drm_device *dev, int stride, int size, int
> tiling_mode)
>  		}
>  	}
>
> +	if (IS_GEN2(dev) ||
> +	    (tiling_mode == I915_TILING_Y && HAS_128_BYTE_Y_TILING(dev)))
> +		tile_height = 32;
> +	else
> +		tile_height = 8;
> +	/* i8xx is strange: It has 2 interleaved rows of tiles, so needs an even
> +	 * number of tile rows. */
> +	if (IS_GEN2(dev))
> +		tile_height *= 2;
> +
> +	/* Size needs to be aligned to a full tile row */
> +	if (size & (tile_height * stride - 1))
> +		return false;
> +
>  	/* 965+ just needs multiples of tile width */
>  	if (INTEL_INFO(dev)->gen >= 4) {
>  		if (stride & (tile_width - 1))

Tested-by: Indan Zupancic <indan at nul.nu>

I tested with this patch and without the other ones you send and the corruption
is indeed gone.

Not sure why you dropped lkml from CC, now people who stuble upon it don't see
the ending...

Greetings,

Indan