JFYI: will try to take a look at this at the start of next week

On Tue, 2021-06-29 at 16:07 -0700, Kuogee Hsieh wrote:

From: Rajkumar Subbiah rsubbia@codeaurora.org

Commit 2f015ec6eab6 ("drm/dp_mst: Add sideband down request tracing + selftests") added some debug code for sideband message tracing. But it seems to have unintentionally changed the behavior on sideband message failure. It catches and returns failure only if DRM_UT_DP is enabled. Otherwise it ignores the error code and returns success. So on an MST unplug, the caller is unaware that the clear payload message failed and ends up waiting for 4 seconds for the response. Fixes the issue by returning the proper error code.

Changes in V2: -- Revise commit text as review comment -- add Fixes text

Fixes: 2f015ec6eab6 ("drm/dp_mst: Add sideband down request tracing + selftests")

Signed-off-by: Rajkumar Subbiah rsubbia@codeaurora.org Signed-off-by: Kuogee Hsieh khsieh@codeaurora.org

Reviewed-by: Stephen Boyd swboyd@chromium.org

drivers/gpu/drm/drm_dp_mst_topology.c | 10 ++++++----  1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 1590144..8d97430 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -2887,11 +2887,13 @@ static int process_single_tx_qlock(struct drm_dp_mst_topology_mgr *mgr,         idx += tosend + 1;           ret = drm_dp_send_sideband_msg(mgr, up, chunk, idx); -       if (unlikely(ret) && drm_debug_enabled(DRM_UT_DP)) { -               struct drm_printer p = drm_debug_printer(DBG_PREFIX); +       if (unlikely(ret)) { +               if (drm_debug_enabled(DRM_UT_DP)) { +                       struct drm_printer p = drm_debug_printer(DBG_PREFIX);   -               drm_printf(&p, "sideband msg failed to send\n"); -               drm_dp_mst_dump_sideband_msg_tx(&p, txmsg); +                       drm_printf(&p, "sideband msg failed to send\n"); +                       drm_dp_mst_dump_sideband_msg_tx(&p, txmsg); +               }                 return ret;         }