drm/radeon/kms: prefer legacy pll algo for tv-out

ntsc seems to work fine with either algo, some
pal TVs seem pickier.

Fixes:
https://bugzilla.kernel.org/show_bug.cgi?id=30832

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/atombios_crtc.c

@@ -957,7 +957,11 @@ static void atombios_crtc_set_pll(struct drm_crtc *crtc, struct drm_display_mode
 	/* adjust pixel clock as needed */
 	adjusted_clock = atombios_adjust_pll(crtc, mode, pll, ss_enabled, &ss);
 
-	if (ASIC_IS_AVIVO(rdev))
+	if (radeon_encoder->active_device & (ATOM_DEVICE_TV_SUPPORT))
+		/* TV seems to prefer the legacy algo on some boards */
+		radeon_compute_pll_legacy(pll, adjusted_clock, &pll_clock, &fb_div, &frac_fb_div,
+					  &ref_div, &post_div);
+	else if (ASIC_IS_AVIVO(rdev))
 		radeon_compute_pll_avivo(pll, adjusted_clock, &pll_clock, &fb_div, &frac_fb_div,
 					 &ref_div, &post_div);
 	else