On Wed, Jun 18, 2025 at 4:23 AM Maxime Ripard <[email protected]> wrote:
> On Wed, Jun 18, 2025 at 10:51:58AM +0200, Luca Ceresoli wrote: > > Hello Anusha, Francesco, > > > > On Tue, 17 Jun 2025 11:17:20 -0500 > > Anusha Srivatsa <[email protected]> wrote: > > > > > On Thu, Jun 12, 2025 at 3:24 AM Francesco Dolcini < > [email protected]> > > > wrote: > > > > > > > Hello all, > > > > > > > > Commit de04bb0089a9 ("drm/panel/panel-simple: Use the new allocation > in > > > > place of devm_kzalloc()") > > > > from 6.16-rc1 introduced a regression with this warning during probe > > > > with panel dpi described in the DT. > > > > > > > > A revert solves the issue. > > > > > > > > The issue is that connector_type is set to DRM_MODE_CONNECTOR_DPI in > > > > panel_dpi_probe() that after that change is called after > > > > devm_drm_panel_alloc(). > > > > > > > > I am not sure if there are other implication for this change in the > call > > > > ordering, apart the one that triggers this warning. > > > > > > > > [ 12.089274] ------------[ cut here ]------------ > > > > [ 12.089303] WARNING: CPU: 0 PID: 96 at > > > > drivers/gpu/drm/bridge/panel.c:377 devm_drm_of_get_bridge+0xac/0xb8 > > > > [ 12.130808] Modules linked in: v4l2_jpeg pwm_imx27(+) imx_vdoa > > > > gpu_sched panel_simple imx6_media(C) imx_media_common > > > > (C) videobuf2_dma_contig pwm_bl gpio_keys v4l2_mem2mem fuse ipv6 > autofs4 > > > > [ 12.147774] CPU: 0 UID: 0 PID: 96 Comm: kworker/u8:3 Tainted: G > > > > C 6.16.0-rc1+ #1 PREEMPT > > > > [ 12.157446] Tainted: [C]=CRAP > > > > [ 12.160418] Hardware name: Freescale i.MX6 Quad/DualLite (Device > Tree) > > > > [ 12.166953] Workqueue: events_unbound deferred_probe_work_func > > > > [ 12.172805] Call trace: > > > > [ 12.172815] unwind_backtrace from show_stack+0x10/0x14 > > > > [ 12.180598] show_stack from dump_stack_lvl+0x68/0x74 > > > > [ 12.185674] dump_stack_lvl from __warn+0x7c/0xe0 > > > > [ 12.190407] __warn from warn_slowpath_fmt+0x1b8/0x1c0 > > > > [ 12.195567] warn_slowpath_fmt from > devm_drm_of_get_bridge+0xac/0xb8 > > > > [ 12.201949] devm_drm_of_get_bridge from imx_pd_probe+0x58/0x164 > > > > [ 12.207976] imx_pd_probe from platform_probe+0x5c/0xb0 > > > > [ 12.213220] platform_probe from really_probe+0xd0/0x3a4 > > > > [ 12.218551] really_probe from __driver_probe_device+0x8c/0x1d4 > > > > [ 12.224486] __driver_probe_device from > driver_probe_device+0x30/0xc0 > > > > [ 12.230942] driver_probe_device from > __device_attach_driver+0x98/0x10c > > > > [ 12.237572] __device_attach_driver from > bus_for_each_drv+0x90/0xe4 > > > > [ 12.243854] bus_for_each_drv from __device_attach+0xa8/0x1c8 > > > > [ 12.249614] __device_attach from bus_probe_device+0x88/0x8c > > > > [ 12.255285] bus_probe_device from > deferred_probe_work_func+0x8c/0xcc > > > > [ 12.261739] deferred_probe_work_func from > process_one_work+0x154/0x2dc > > > > [ 12.268371] process_one_work from worker_thread+0x250/0x3f0 > > > > [ 12.274043] worker_thread from kthread+0x12c/0x24c > > > > [ 12.278940] kthread from ret_from_fork+0x14/0x28 > > > > [ 12.283660] Exception stack(0xd0be9fb0 to 0xd0be9ff8) > > > > [ 12.288720] 9fa0: 00000000 > 00000000 > > > > 00000000 00000000 > > > > [ 12.296906] 9fc0: 00000000 00000000 00000000 00000000 00000000 > 00000000 > > > > 00000000 00000000 > > > > [ 12.305089] 9fe0: 00000000 00000000 00000000 00000000 00000013 > 00000000 > > > > [ 12.312050] ---[ end trace 0000000000000000 ]--- > > > > > > > > #regzbot ^introduced: de04bb0089a96cc00d13b12cbf66a088befe3057 > > > > > > > > Any advise? > > > > > > > > Hey Francesco! > > > > > > This mail reached my spam and I hadn't realised till today. Thanks for > > > bringing this to attention. > > > > > > Thinking out loud here: If we called dpi_probe() before allocating the > > > panel using devm_drm_panel_alloc() > > > then we would have the connector type. But dpi_probe() needs the > panel to > > > be allocated.... > > > > Reading the panel-simple.c code, the handling of the panel_dsi > > descriptor feels a bit hacky, and the recent change to > > devm_drm_panel_alloc() breaks it easily. Perhaps it would be cleaner to > > assess the whole descriptor before ding any allocation/init. > > > > You're right tat panel_dpi_probe() needs the panel, but it's only at the > > very end, to assign the descriptor: > > > > panel->desc = desc; > > > > I think a good fix would be to clean it up by having: > > > > * panel_dpi_probe() not take a panel pointer but rather returning a > > filled descriptor > > * panel_simple_probe() call panel_dpi_probe() early [before > > devm_drm_panel_alloc()] and get the filled descriptor > > * call devm_drm_panel_alloc() with that descriptor in the panel-dsi > > case, or with the good old descriptor otherwise > > > > As a good side effect, it would get rid of a case where > > devm_drm_panel_alloc() is called with a Unknown connector type. > > > > Anusha, does it look like a good plan? > > It is, and I'd even go one step further. Like you said, panel_dpi_probe > kind of exists to allocate and initialize the panel descriptor, and is > called on the descriptor being equal to the (uninitialized) panel_dpi > global variable. > > We should also get rid of that hack, so do something like creating a > function that returns the descriptor, and is indeed called first in > panel_simple_probe. It first calls of_device_get_match_data(), and if > there's no match, and if the device is compatible with panel-dpi, then > it calls panel_dpi_probe (we should probably change that name too). That > way, we can get rid of the panel_dpi variable entirely. > > Thanks Luca and Maxime. To summarize: 1. add a function like of_device_get_simple_dsi_match_data() which calls of_device_get_match_data(). if the device is compatible with panel-dpi, call panel-dpi-probe() 3. Change panel_dpi_probe() to return the panel descriptor 4. call devm_drm_panel_alloc() Thanks, Anusha > Maxime >
