<div dir="ltr"><div dir="ltr"><br></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Thu, Jun 12, 2025 at 3:24 AM Francesco Dolcini <<a href="mailto:francesco@dolcini.it">francesco@dolcini.it</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hello all,<br>
<br>
Commit de04bb0089a9 ("drm/panel/panel-simple: Use the new allocation in place of devm_kzalloc()")<br>
from 6.16-rc1 introduced a regression with this warning during probe<br>
with panel dpi described in the DT.<br>
<br>
A revert solves the issue.<br>
<br>
The issue is that connector_type is set to DRM_MODE_CONNECTOR_DPI in<br>
panel_dpi_probe() that after that change is called after<br>
devm_drm_panel_alloc().<br>
<br>
I am not sure if there are other implication for this change in the call<br>
ordering, apart the one that triggers this warning.<br>
<br></blockquote><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
[ 12.089274] ------------[ cut here ]------------<br>
[ 12.089303] WARNING: CPU: 0 PID: 96 at drivers/gpu/drm/bridge/panel.c:377 devm_drm_of_get_bridge+0xac/0xb8<br>
[ 12.130808] Modules linked in: v4l2_jpeg pwm_imx27(+) imx_vdoa gpu_sched panel_simple imx6_media(C) imx_media_common<br>
(C) videobuf2_dma_contig pwm_bl gpio_keys v4l2_mem2mem fuse ipv6 autofs4<br>
[ 12.147774] CPU: 0 UID: 0 PID: 96 Comm: kworker/u8:3 Tainted: G C 6.16.0-rc1+ #1 PREEMPT<br>
[ 12.157446] Tainted: [C]=CRAP<br>
[ 12.160418] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)<br>
[ 12.166953] Workqueue: events_unbound deferred_probe_work_func<br>
[ 12.172805] Call trace:<br>
[ 12.172815] unwind_backtrace from show_stack+0x10/0x14<br>
[ 12.180598] show_stack from dump_stack_lvl+0x68/0x74<br>
[ 12.185674] dump_stack_lvl from __warn+0x7c/0xe0<br>
[ 12.190407] __warn from warn_slowpath_fmt+0x1b8/0x1c0<br>
[ 12.195567] warn_slowpath_fmt from devm_drm_of_get_bridge+0xac/0xb8<br>
[ 12.201949] devm_drm_of_get_bridge from imx_pd_probe+0x58/0x164<br>
[ 12.207976] imx_pd_probe from platform_probe+0x5c/0xb0<br>
[ 12.213220] platform_probe from really_probe+0xd0/0x3a4<br>
[ 12.218551] really_probe from __driver_probe_device+0x8c/0x1d4<br>
[ 12.224486] __driver_probe_device from driver_probe_device+0x30/0xc0<br>
[ 12.230942] driver_probe_device from __device_attach_driver+0x98/0x10c<br>
[ 12.237572] __device_attach_driver from bus_for_each_drv+0x90/0xe4<br>
[ 12.243854] bus_for_each_drv from __device_attach+0xa8/0x1c8<br>
[ 12.249614] __device_attach from bus_probe_device+0x88/0x8c<br>
[ 12.255285] bus_probe_device from deferred_probe_work_func+0x8c/0xcc<br>
[ 12.261739] deferred_probe_work_func from process_one_work+0x154/0x2dc<br>
[ 12.268371] process_one_work from worker_thread+0x250/0x3f0<br>
[ 12.274043] worker_thread from kthread+0x12c/0x24c<br>
[ 12.278940] kthread from ret_from_fork+0x14/0x28<br>
[ 12.283660] Exception stack(0xd0be9fb0 to 0xd0be9ff8)<br>
[ 12.288720] 9fa0: 00000000 00000000 00000000 00000000<br>
[ 12.296906] 9fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000<br>
[ 12.305089] 9fe0: 00000000 00000000 00000000 00000000 00000013 00000000<br>
[ 12.312050] ---[ end trace 0000000000000000 ]---<br>
<br>
#regzbot ^introduced: de04bb0089a96cc00d13b12cbf66a088befe3057<br>
<br>
Any advise?<br>
<br></blockquote><div>Hey Francesco!</div><div> <br></div><div><div>This mail reached my spam and I hadn't realised till today. Thanks for bringing this to attention.</div><div><br></div><div>Thinking out loud here: If we called dpi_probe() before allocating the panel using devm_drm_panel_alloc()</div><div>then we would have the connector type. But dpi_probe() needs the panel to be allocated....</div><div><br></div><div>We could actually hardcode the connector type to DRM_MODE_CONNECTOR_DPI....</div><div>Looking at panel_dpi_probe(), it guesses the connector_type:</div><div><pre><span id="gmail-codeline-473"><span class="gmail-w"></span><span class="gmail-cm">/* We do not know the connector for the DT node, so guess it */</span>
</span><span id="gmail-codeline-474"><span class="gmail-w"> </span><span class="gmail-n">desc</span><span class="gmail-o">-></span><span class="gmail-n"><a class="gmail-ident" href="https://elixir.bootlin.com/linux/v6.16-rc2/C/ident/connector_type">connector_type</a></span><span class="gmail-w"> </span><span class="gmail-o">=</span><span class="gmail-w"> </span><span class="gmail-n"><a class="gmail-ident" href="https://elixir.bootlin.com/linux/v6.16-rc2/C/ident/DRM_MODE_CONNECTOR_DPI">DRM_MODE_CONNECTOR_DPI</a></span><span class="gmail-p">;</span></span></pre></div><div><br></div><div>Reverting will improve the end user experience but if the fix can be quick, we can</div><div>avoid dropping the change</div><div><br></div><div>Thanks,</div><div>Anusha</div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
Francesco<br>
<br>
</blockquote></div></div>