<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <style type="text/css" style="display:none;"> P {margin-top:0;margin-bottom:0;} </style> </head> <body dir="ltr"> <p style="font-family:Arial;font-size:10pt;color:#0078D7;margin:15pt;" align="Left"> [AMD Official Use Only - Internal Distribution Only]<br> </p> <br> <div> <div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)"> I took a closer look at this and there seems to be an issue in the function. <br> </div> <div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)"> <br> </div> <div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)"> Crtc being null is a valid case here. The sequence that leads to this is, unplug -> disable crtc/release vcpi slots then hotplug. The issue is that pos->port is not guaranteed to be released in <b>drm_dp_atomic_release_vcpi_slots()</b> so <b>list_for_each_entry(pos, &mst_state->vcpis, next) {} </b>might still iterate thought it.<br> </div> <div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)"> <br> </div> <div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)"> So, when a hotplug is done we still loop through the old port which has port! = null, crtc = null, and vpci = 0. I didn't find anything that I can use to remove the port from the list. So, a potential solution to this would be to add a<span> check for vpci = 0 and skip that port.<br> </span></div> <div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)"> <span></span><span></span><br> </div> <div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)"> Thoughts/Suggestions?<br> </div> <div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)"> <br> </div> <div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)"> Bhawan<br> </div> <div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)"> <br> </div> <div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)"> <br> </div> <div id="appendonsend"></div> <div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)"> <br> </div> <hr tabindex="-1" style="display:inline-block; width:98%"> <div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>From:</b> amd-gfx <amd-gfx-bounces@lists.freedesktop.org> on behalf of Lakha, Bhawanpreet <Bhawanpreet.Lakha@amd.com><br> <b>Sent:</b> August 14, 2020 2:52 PM<br> <b>To:</b> Ruhl, Michael J <michael.j.ruhl@intel.com>; Lipski, Mikita <Mikita.Lipski@amd.com>; Kazlauskas, Nicholas <Nicholas.Kazlauskas@amd.com>; Deucher, Alexander <Alexander.Deucher@amd.com><br> <b>Cc:</b> amd-gfx@lists.freedesktop.org <amd-gfx@lists.freedesktop.org>; dri-devel@lists.freedesktop.org <dri-devel@lists.freedesktop.org><br> <b>Subject:</b> Re: [PATCH] drm/dp_mst: Don't return error code when crtc is null</font> <div dir="ltr"> <br> <div> <div> <div><br> </div> <div>pos->port->connector?</div> <div>This is checking the crtc not the connector. The crtc can be null if its disabled.<br> </div> <div><br> </div> <div> <div>Since it is happening after a unplug->hotplug, I guess we are missing something in the disable sequence and the old connector is still in the list.<br> </div> </div> <div><br> </div> <div>Bhawan</div> <div><br> </div> <div>>>-----Original Message-----<br> </div> <div>>>From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of</div> <div>>>Bhawanpreet Lakha</div> <div>>>Sent: Friday, August 14, 2020 1:02 PM</div> <div>>>To: mikita.lipski@amd.com; nicholas.kazlauskas@amd.com;</div> <div>>>alexander.deucher@amd.com</div> <div>>>Cc: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>; dri-</div> <div>>>devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org</div> <div>>>Subject: [PATCH] drm/dp_mst: Don't return error code when crtc is null</div> <div>>></div> <div>>>[Why]</div> <div>>>In certain cases the crtc can be NULL and returning -EINVAL causes</div> <div>>>atomic check to fail when it shouln't. This leads to valid</div> <div>>>configurations failing because atomic check fails.</div> <div>></div> <div>>So is this a bug fix or an exception case, or an expected possibility?</div> <div>></div> <div>>From my reading of the function comments, it is not clear that pos->port->connector</div> <div>>might be NULL for some reason.</div> <br> <div>>A better explanation of why this would occur would make this a much more</div> <div>>useful commit message.</div> <div>></div> <div><br> </div> <div>>My reading is that you ran into this issue an are masking it with this fix.</div> <div>></div> <div>>Rather than this is a real possibility and this is the correct fix.</div> <div>></div> <div>>Mike</div> <div>></div> <div>>>[How]</div> <div>>>Don't early return if crtc is null</div> <div>>></div> <div>>>Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com></div> <div>>>---</div> <div>>> drivers/gpu/drm/drm_dp_mst_topology.c | 4 ++--</div> <div>>> 1 file changed, 2 insertions(+), 2 deletions(-)</div> <div>>></div> <div>>>diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c</div> <div>>>b/drivers/gpu/drm/drm_dp_mst_topology.c</div> <div>>>index 70c4b7afed12..bc90a1485699 100644</div> <div>>>--- a/drivers/gpu/drm/drm_dp_mst_topology.c</div> <div>>>+++ b/drivers/gpu/drm/drm_dp_mst_topology.c</div> <div>>>@@ -5037,8 +5037,8 @@ int drm_dp_mst_add_affected_dsc_crtcs(struct</div> <div>>>drm_atomic_state *state, struct drm</div> <div>>></div> <div>>> crtc = conn_state->crtc;</div> <div>>></div> <div>>>- if (WARN_ON(!crtc))</div> <div>>>- return -EINVAL;</div> <div>>>+ if (!crtc)</div> <div>>>+ continue;</div> <div>>></div> <div>>> if (!drm_dp_mst_dsc_aux_for_port(pos->port))</div> <div>>> continue;</div> <div>>>--</div> <div>>>2.17.1</div> <div>>></div> <div>>>_______________________________________________</div> <div>>>dri-devel mailing list</div> <div>>>dri-devel@lists.freedesktop.org</div> <div>>>https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.freedesktop.org%2Fmailman%2Flistinfo%2Fdri-devel&data=02%7C01%7CBhawanpreet.Lakha%40amd.com%7C0f5d55c551644fef3df908d840787b3e%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637330233520819407&sdata=5N%2BBb0Qp3bd5zANfxovb%2BrVLAGnbP1sjyw3EeCHXj2w%3D&reserved=0 <br> </div> </div> </div> </div> </div> </div> </body> </html>