From a81b2acd43e24e419f65df97348c76a5a1496066 Mon Sep 17 00:00:00 2001 From: Jammy Huang Date: Wed, 3 Apr 2024 17:02:46 +0800 Subject: [PATCH] drm/ast: Fix soft lockup 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 Fixes: 594e9c04b586 ("drm/ast: Create the driver for ASPEED proprietory Display-Port") Reviewed-by: Jocelyn Falempe Reviewed-by: Thomas Zimmermann Signed-off-by: Thomas Zimmermann Cc: KuoHsiang Chou Cc: Thomas Zimmermann Cc: Dave Airlie Cc: Jocelyn Falempe Cc: dri-devel@lists.freedesktop.org Cc: # v5.19+ Link: https://patchwork.freedesktop.org/patch/msgid/20240403090246.1495487-1-jammy_huang@aspeedtech.com Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/ast/ast_dp.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/gpu/drm/ast/ast_dp.c b/drivers/gpu/drm/ast/ast_dp.c index fdd9a493aa9c0..c6f226b6f0813 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_CRTC_PORT, 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; } } } -- 2.47.3