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    Subject[PATCH 4.1 143/267] drm/i915: Declare the swizzling unknown for L-shaped configurations
    Date
    4.1-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Chris Wilson <chris@chris-wilson.co.uk>

    commit 19ee835cdb0b5a8eb11a68f25a51b8039d564488 upstream.

    The old style of memory interleaving swizzled upto the end of the
    first even bank of memory, and then used the remainder as unswizzled on
    the unpaired bank - i.e. swizzling is not constant for all memory. This
    causes problems when we try to migrate memory and so the kernel prevents
    migration at all when we detect L-shaped inconsistent swizzling.
    However, this issue also extends to userspace who try to manually detile
    into memory as the swizzling for an individual page is unknown (it
    depends on its physical address only known to the kernel), userspace
    cannot correctly swizzle objects.

    v2: Mark the global swizzling as unknown rather than adjust the value
    reported to userspace.

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91105
    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
    Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
    Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/gpu/drm/i915/i915_gem_tiling.c | 12 +++++++++++-
    1 file changed, 11 insertions(+), 1 deletion(-)

    --- a/drivers/gpu/drm/i915/i915_gem_tiling.c
    +++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
    @@ -183,8 +183,18 @@ i915_gem_detect_bit_6_swizzle(struct drm
    if (IS_GEN4(dev)) {
    uint32_t ddc2 = I915_READ(DCC2);

    - if (!(ddc2 & DCC2_MODIFIED_ENHANCED_DISABLE))
    + if (!(ddc2 & DCC2_MODIFIED_ENHANCED_DISABLE)) {
    + /* Since the swizzling may vary within an
    + * object, we have no idea what the swizzling
    + * is for any page in particular. Thus we
    + * cannot migrate tiled pages using the GPU,
    + * nor can we tell userspace what the exact
    + * swizzling is for any object.
    + */
    dev_priv->quirks |= QUIRK_PIN_SWIZZLED_PAGES;
    + swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
    + swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
    + }
    }

    if (dcc == 0xffffffff) {



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