6.8-stable review patch. If anyone has any objections, please let me know.
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From: Jammy Huang jammy_huang@aspeedtech.com
commit bc004f5038220b1891ef4107134ccae44be55109 upstream.
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... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/ast/ast_dp.c | 3 +++ 1 file changed, 3 insertions(+)
--- 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 { 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 ASTDP_MIRROR_VIDEO_ENABLE) != video_on_off) { // wait 1 ms mdelay(1); + if (++i > 200) + break; } } }