Hi Greg,
Am 11.11.2025 um 01:34 schrieb Greg Kroah-Hartman:
6.17-stable review patch. If anyone has any objections, please let me know.
------------------
From: Thomas Zimmermann <[email protected]>
commit a9fb41b5def8e1e0103d5fd1453787993587281e upstream.
Preserve the I/O register bits in __ast_write8_i_masked() as specified
by preserve_mask. Accidentally OR-ing the output value into these will
overwrite the register's previous settings.
Fixes display output on the AST2300, where the screen can go blank at
boot. The driver's original commit 312fec1405dd ("drm: Initial KMS
driver for AST (ASpeed Technologies) 2000 series (v2)") already added
the broken code. Commit 6f719373b943 ("drm/ast: Blank with VGACR17 sync
enable, always clear VGACRB6 sync off") triggered the bug.
Signed-off-by: Thomas Zimmermann <[email protected]>
Reported-by: Peter Schneider <[email protected]>
Closes:
https://lore.kernel.org/dri-devel/[email protected]/
Tested-by: Peter Schneider <[email protected]>
Reviewed-by: Jocelyn Falempe <[email protected]>
Fixes: 6f719373b943 ("drm/ast: Blank with VGACR17 sync enable, always clear VGACRB6
sync off")
Fixes: 312fec1405dd ("drm: Initial KMS driver for AST (ASpeed Technologies) 2000
series (v2)")
Cc: Thomas Zimmermann <[email protected]>
Cc: Nick Bowler <[email protected]>
Cc: Douglas Anderson <[email protected]>
Cc: Dave Airlie <[email protected]>
Cc: Jocelyn Falempe <[email protected]>
Cc: [email protected]
Cc: <[email protected]> # v3.5+
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/gpu/drm/ast/ast_drv.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/drivers/gpu/drm/ast/ast_drv.h
+++ b/drivers/gpu/drm/ast/ast_drv.h
@@ -284,13 +284,13 @@ static inline void __ast_write8_i(void _
__ast_write8(addr, reg + 1, val);
}
-static inline void __ast_write8_i_masked(void __iomem *addr, u32 reg, u8 index, u8 read_mask,
+static inline void __ast_write8_i_masked(void __iomem *addr, u32 reg, u8
index, u8 preserve_mask,
u8 val)
{
- u8 tmp = __ast_read8_i_masked(addr, reg, index, read_mask);
+ u8 tmp = __ast_read8_i_masked(addr, reg, index, preserve_mask);
- tmp |= val;
- __ast_write8_i(addr, reg, index, tmp);
+ val &= ~preserve_mask;
+ __ast_write8_i(addr, reg, index, tmp | val);
}
static inline u32 ast_read32(struct ast_device *ast, u32 reg)
I think that with this patch (which fixes a bug in the original ast driver affecting AST2300), it is now safe to also
include (in both 6.12.58 AND 6.17.8)
6f719373b943 ("drm/ast: Blank with VGACR17 sync enable, always clear VGACRB6 sync
off")
which triggered that bug, and which you dropped from 6.12.55 and 6.17.5,
respectively, because of my report
https://lore.kernel.org/dri-devel/[email protected]/
NB: 6f719373b943 fixed (IIRC) an important issue for AST2500 users. I have tested the combination of both patches in
mainline 6.18-rc2, and they work fine together, and Linus has both of them in his tree since 6.18-rc4.
Also, I tested both of them already on top of 6.12.5 and 6.17.5, and they were
fine, too. Please see:
https://lore.kernel.org/lkml/[email protected]/
Beste Grüße,
Peter Schneider
--
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enjoy the air and behold the view. Climb it so you can see the world,
not so the world can see you. -- David McCullough Jr.
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