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authorJammy Huang <jammy_huang@aspeedtech.com>2024-04-03 17:02:46 +0800
committerThomas Zimmermann <tzimmermann@suse.de>2024-04-05 10:22:23 +0200
commitbc004f5038220b1891ef4107134ccae44be55109 (patch)
tree36bc57cb303445c73b3d34041278058c65538cae
parent1fc9af813b25e146d3607669247d0f970f5a87c3 (diff)
drm/ast: Fix soft lockup
There is a while-loop in ast_dp_set_on_off() that could lead to infinite-loop. This is because the register, VGACRI-Dx, checked in this API is a scratch register actually controlled by a MCU, named DPMCU, in BMC. These scratch registers are protected by scu-lock. If suc-lock is not off, DPMCU can not update these registers and then host will have soft lockup due to never updated status. DPMCU is used to control DP and relative registers to handshake with host's VGA driver. Even the most time-consuming task, DP's link training, is less than 100ms. 200ms should be enough. Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com> Fixes: 594e9c04b586 ("drm/ast: Create the driver for ASPEED proprietory Display-Port") Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com> Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Cc: KuoHsiang Chou <kuohsiang_chou@aspeedtech.com> Cc: Thomas Zimmermann <tzimmermann@suse.de> Cc: Dave Airlie <airlied@redhat.com> Cc: Jocelyn Falempe <jfalempe@redhat.com> Cc: dri-devel@lists.freedesktop.org Cc: <stable@vger.kernel.org> # v5.19+ Link: https://patchwork.freedesktop.org/patch/msgid/20240403090246.1495487-1-jammy_huang@aspeedtech.com
-rw-r--r--drivers/gpu/drm/ast/ast_dp.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/gpu/drm/ast/ast_dp.c b/drivers/gpu/drm/ast/ast_dp.c
index ebb6d8ebd44e..1e9259416980 100644
--- a/drivers/gpu/drm/ast/ast_dp.c
+++ b/drivers/gpu/drm/ast/ast_dp.c
@@ -180,6 +180,7 @@ void ast_dp_set_on_off(struct drm_device *dev, bool on)
{
struct ast_device *ast = to_ast_device(dev);
u8 video_on_off = on;
+ u32 i = 0;
// Video On/Off
ast_set_index_reg_mask(ast, AST_IO_VGACRI, 0xE3, (u8) ~AST_DP_VIDEO_ENABLE, on);
@@ -192,6 +193,8 @@ void ast_dp_set_on_off(struct drm_device *dev, bool on)
ASTDP_MIRROR_VIDEO_ENABLE) != video_on_off) {
// wait 1 ms
mdelay(1);
+ if (++i > 200)
+ break;
}
}
}