drm/radeon: use frac fb div on RS780/RS880

commit 411678288d61ba17afe1f8afed92200be6bbc65d upstream.

Monitors seem to prefer it.  Fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=37696

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[bwh: Backported to 3.2:
 - Adjust context
 - Add to pll->flags, not radeon_crtc->pll_flags]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Weng Meiling <wengmeiling.weng@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/radeon/atombios_crtc.c b/drivers/gpu/drm/radeon/atombios_crtc.c
index 77dc799..dc612ef 100644 (file)
--- a/drivers/gpu/drm/radeon/atombios_crtc.c
+++ b/drivers/gpu/drm/radeon/atombios_crtc.c
@@ -573,6 +573,9 @@ static u32 atombios_adjust_pll(struct drm_crtc *crtc,
                /* use frac fb div on APUs */
                if (ASIC_IS_DCE41(rdev) || ASIC_IS_DCE61(rdev))
                        pll->flags |= RADEON_PLL_USE_FRAC_FB_DIV;
+               /* use frac fb div on RS780/RS880 */
+               if ((rdev->family == CHIP_RS780) || (rdev->family == CHIP_RS880))
+                       pll->flags |= RADEON_PLL_USE_FRAC_FB_DIV;
                if (ASIC_IS_DCE32(rdev) && mode->clock > 165000)
                        pll->flags |= RADEON_PLL_USE_FRAC_FB_DIV;
        } else {