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    Subject[PATCH 5.11 622/775] drm/modes: Switch to 64bit maths to avoid integer overflow
    Date
    From: Ville Syrjälä <ville.syrjala@linux.intel.com>

    commit 5b34ab52401f0f1f191bcb83a182c83b506f4763 upstream.

    The new >8k CEA modes have dotclocks reaching 5.94 GHz, which
    means our clock*1000 will now overflow the 32bit unsigned
    integer. Switch to 64bit maths to avoid it.

    Cc: stable@vger.kernel.org
    Reported-by: Randy Dunlap <rdunlap@infradead.org>
    Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20201022194256.30978-1-ville.syrjala@linux.intel.com
    Tested-by: Randy Dunlap <rdunlap@infradead.org>
    Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/gpu/drm/drm_modes.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/drivers/gpu/drm/drm_modes.c
    +++ b/drivers/gpu/drm/drm_modes.c
    @@ -762,7 +762,7 @@ int drm_mode_vrefresh(const struct drm_d
    if (mode->htotal == 0 || mode->vtotal == 0)
    return 0;

    - num = mode->clock * 1000;
    + num = mode->clock;
    den = mode->htotal * mode->vtotal;

    if (mode->flags & DRM_MODE_FLAG_INTERLACE)
    @@ -772,7 +772,7 @@ int drm_mode_vrefresh(const struct drm_d
    if (mode->vscan > 1)
    den *= mode->vscan;

    - return DIV_ROUND_CLOSEST(num, den);
    + return DIV_ROUND_CLOSEST_ULL(mul_u32_u32(num, 1000), den);
    }
    EXPORT_SYMBOL(drm_mode_vrefresh);


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