drm/radeon/kms: update new pll algo

- add support for pre-avivo chips
- add support for fixed post/ref dividers
- add support for non-fractional fb dividers

By default avivo chips use the new algo and
pre-avivo chips use the old algo. Use the "new_pll"
module option to toggle between them.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/radeon_legacy_crtc.c b/drivers/gpu/drm/radeon/radeon_legacy_crtc.c
index 6432517..df23d6a 100644
--- a/drivers/gpu/drm/radeon/radeon_legacy_crtc.c
+++ b/drivers/gpu/drm/radeon/radeon_legacy_crtc.c
@@ -703,7 +703,10 @@
 		pll = &rdev->clock.p1pll;
 
 	pll->flags = RADEON_PLL_LEGACY;
-	pll->algo = PLL_ALGO_LEGACY;
+	if (radeon_new_pll == 1)
+		pll->algo = PLL_ALGO_NEW;
+	else
+		pll->algo = PLL_ALGO_LEGACY;
 
 	if (mode->clock > 200000) /* range limits??? */
 		pll->flags |= RADEON_PLL_PREFER_HIGH_FB_DIV;