6.6-stable review patch. If anyone has any objections, please let me know.
------------------ From: Jammy Huang <[email protected]> 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 <[email protected]> Fixes: 594e9c04b586 ("drm/ast: Create the driver for ASPEED proprietory Display-Port") Reviewed-by: Jocelyn Falempe <[email protected]> Reviewed-by: Thomas Zimmermann <[email protected]> Signed-off-by: Thomas Zimmermann <[email protected]> Cc: KuoHsiang Chou <[email protected]> Cc: Thomas Zimmermann <[email protected]> Cc: Dave Airlie <[email protected]> Cc: Jocelyn Falempe <[email protected]> Cc: [email protected] Cc: <[email protected]> # v5.19+ Link: https://patchwork.freedesktop.org/patch/msgid/[email protected] Signed-off-by: Greg Kroah-Hartman <[email protected]> --- 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_CRTC_PORT, 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; } } }
