From: Rajkumar Subbiah rsubbia@codeaurora.org
commit 92bd92c44d0d9be5dcbcda315b4be4b909ed9740 upstream.
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
Changes in V3: -- remove "unlikely" optimization
Fixes: 2f015ec6eab6 ("drm/dp_mst: Add sideband down request tracing + selftests") Cc: stable@vger.kernel.org # v5.5+ Signed-off-by: Rajkumar Subbiah rsubbia@codeaurora.org Signed-off-by: Kuogee Hsieh khsieh@codeaurora.org Reviewed-by: Stephen Boyd swboyd@chromium.org Reviewed-by: Jani Nikula jani.nikula@intel.com Reviewed-by: Lyude Paul lyude@redhat.com Signed-off-by: Lyude Paul lyude@redhat.com Link: https://patchwork.freedesktop.org/patch/msgid/1625585434-9562-1-git-send-ema... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/drm_dp_mst_topology.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
--- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -2869,11 +2869,13 @@ static int process_single_tx_qlock(struc 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 (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; }