commit b389286d0234e1edbaf62ed8bc0892a568c33662 upstream.
For G200_SE_A, PLL M setting is wrong, which leads to blank screen,
or "signal out of range" on VGA display.
previous code had "m |= 0x80" which was changed to
m |= ((pixpllcn & BIT(8)) >> 1);
Tested on G200_SE_A rev 42
This line of code was moved to another file with
commit 877507bb954e ("drm/mgag200: Provide per-device callbacks for
PIXPLLC") but can be easily backported before this commit.
v2: * put BIT(7) First to respect MSB-to-LSB (Thomas)
* Add a comment to explain that this bit must be set (Thomas)
backported to v6.0.17, it also applies cleanly to v5.15.86
Fixes: 2dd040946ecf ("drm/mgag200: Store values (not bits) in struct mgag200_pll_values")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jocelyn Falempe <jfalempe@xxxxxxxxxx>
Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20221013132810.521945-1-jfalempe@xxxxxxxxxx
---
drivers/gpu/drm/mgag200/mgag200_pll.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/mgag200/mgag200_pll.c b/drivers/gpu/drm/mgag200/mgag200_pll.c
index 8065ca5d8de9..4f55961848a8 100644
--- a/drivers/gpu/drm/mgag200/mgag200_pll.c
+++ b/drivers/gpu/drm/mgag200/mgag200_pll.c
@@ -269,7 +269,8 @@ static void mgag200_pixpll_update_g200se_04(struct mgag200_pll *pixpll,
pixpllcp = pixpllc->p - 1;
pixpllcs = pixpllc->s;
- xpixpllcm = pixpllcm | ((pixpllcn & BIT(8)) >> 1);
+ // For G200SE A, BIT(7) should be set unconditionally.
+ xpixpllcm = BIT(7) | pixpllcm;
xpixpllcn = pixpllcn;
xpixpllcp = (pixpllcs << 3) | pixpllcp;
--
2.38.1
