drm/radeon/kms: force legacy pll algo for RV620 LVDS

commit f90087eea44ce5fad139f086bc9d89ca37b0edc2 upstream.

There has been periodic evidence that LVDS, on at least some
panels, prefers the dividers selected by the legacy pll algo.
This patch forces the use of the legacy pll algo on RV620
LVDS panels.  The old behavior (new pll algo) can be selected
by setting the new_pll module parameter to 1.

Fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=30029

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/gpu/drm/radeon/atombios_crtc.c b/drivers/gpu/drm/radeon/atombios_crtc.c
index 3271b5a3421f8cecb35dfc3a16ebe62013e63393..eac868a6cd116769c1f76de5afa4f14663cd5fac 100644 (file)
--- a/drivers/gpu/drm/radeon/atombios_crtc.c
+++ b/drivers/gpu/drm/radeon/atombios_crtc.c
@@ -527,14 +527,15 @@ static u32 atombios_adjust_pll(struct drm_crtc *crtc,
                                        pll->algo = PLL_ALGO_LEGACY;
                                        pll->flags |= RADEON_PLL_PREFER_CLOSEST_LOWER;
                                }
-                               /* There is some evidence (often anecdotal) that RV515 LVDS
+                               /* There is some evidence (often anecdotal) that RV515/RV620 LVDS
                                 * (on some boards at least) prefers the legacy algo.  I'm not
                                 * sure whether this should handled generically or on a
                                 * case-by-case quirk basis.  Both algos should work fine in the
                                 * majority of cases.
                                 */
                                if ((radeon_encoder->active_device & (ATOM_DEVICE_LCD_SUPPORT)) &&
-                                   (rdev->family == CHIP_RV515)) {
+                                   ((rdev->family == CHIP_RV515) ||
+                                    (rdev->family == CHIP_RV620))) {
                                        /* allow the user to overrride just in case */
                                        if (radeon_new_pll == 1)
                                                pll->algo = PLL_ALGO_NEW;