a9fb41b5de
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 commit312fec1405("drm: Initial KMS driver for AST (ASpeed Technologies) 2000 series (v2)") already added the broken code. Commit6f719373b9("drm/ast: Blank with VGACR17 sync enable, always clear VGACRB6 sync off") triggered the bug. Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Reported-by: Peter Schneider <pschneider1968@googlemail.com> Closes: https://lore.kernel.org/dri-devel/a40caf8e-58ad-4f9c-af7f-54f6f69c29bb@googlemail.com/ Tested-by: Peter Schneider <pschneider1968@googlemail.com> Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com> Fixes:6f719373b9("drm/ast: Blank with VGACR17 sync enable, always clear VGACRB6 sync off") Fixes:312fec1405("drm: Initial KMS driver for AST (ASpeed Technologies) 2000 series (v2)") Cc: Thomas Zimmermann <tzimmermann@suse.de> Cc: Nick Bowler <nbowler@draconx.ca> Cc: Douglas Anderson <dianders@chromium.org> Cc: Dave Airlie <airlied@redhat.com> Cc: Jocelyn Falempe <jfalempe@redhat.com> Cc: dri-devel@lists.freedesktop.org Cc: <stable@vger.kernel.org> # v3.5+ Link: https://patch.msgid.link/20251024073626.129032-1-tzimmermann@suse.de