Re: [BUG] drm/panel: ilitek-ili9881c: kernel panic on reboot

[Claudiu Beznea <claudiu.beznea@tuxon.dev>]

Hi, Hugo,

On 1/7/26 23:48, Hugo Villeneuve wrote:
> Hi,
> when issuing a reboot command, I encounter the following kernel panic:
> 
> [   36.183478] SError Interrupt on CPU1, code 0x00000000be000011 -- SError
> [   36.183492] CPU: 1 UID: 0 PID: 1 Comm: systemd-shutdow Tainted: G   M                6.19.0-rc4-arm64-renesas-00019-g067a81578add #62 NONE
> [   36.183504] Tainted: [M]=MACHINE_CHECK
> [   36.183507] Hardware name: Gecko ECO2 nxtpad (DT)
> [   36.183512] pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [   36.183519] pc : rzg2l_mipi_dsi_host_transfer+0x114/0x458
> [   36.183538] lr : rzg2l_mipi_dsi_host_transfer+0x98/0x458
> [   36.183547] sp : ffff8000813db860
> [   36.183550] x29: ffff8000813db890 x28: ffff800080c602c0 x27: ffff000009dd7450
> [   36.183563] x26: ffff800080c5fcc0 x25: ffff000009dd7450 x24: ffff800080e1f7a8
> [   36.183573] x23: ffff000009dd7400 x22: 0000000000000000 x21: ffff000009dd7430
> [   36.183582] x20: ffff8000813db8e8 x19: 0000000002050028 x18: 00000000ffffffff
> [   36.183592] x17: 0000000000000000 x16: 0000000000000000 x15: ffff8000813db220
> [   36.183602] x14: 0000000000000000 x13: ffff800081255bc0 x12: 00000000000009a2
> [   36.183611] x11: 0000000000000336 x10: ffff8000812b28d0 x9 : ffff800081255bc0
> [   36.183621] x8 : ffff800081399000 x7 : ffff00000a042600 x6 : 0000000000000000
> [   36.183631] x5 : 0000000000000805 x4 : 0000000002000000 x3 : 0000000000000028
> [   36.183640] x2 : 0000000049627000 x1 : ffff800080c60b40 x0 : ffff800081780000
> [   36.183652] Kernel panic - not syncing: Asynchronous SError Interrupt
> [   36.183657] CPU: 1 UID: 0 PID: 1 Comm: systemd-shutdow Tainted: G   M                6.19.0-rc4-arm64-renesas-00019-g067a81578add #62 NONE
> [   36.183665] Tainted: [M]=MACHINE_CHECK
> [   36.183668] Hardware name: devboard1 (DT)
> [   36.183672] Call trace:
> [   36.183675]  show_stack+0x18/0x24 (C)
> [   36.183692]  dump_stack_lvl+0x34/0x8c
> [   36.183702]  dump_stack+0x18/0x24
> [   36.183708]  vpanic+0x314/0x35c
> [   36.183716]  nmi_panic+0x0/0x64
> [   36.183722]  add_taint+0x0/0xbc
> [   36.183728]  arm64_serror_panic+0x70/0x80
> [   36.183735]  do_serror+0x28/0x68
> [   36.183742]  el1h_64_error_handler+0x34/0x50
> [   36.183751]  el1h_64_error+0x6c/0x70
> [   36.183758]  rzg2l_mipi_dsi_host_transfer+0x114/0x458 (P)
> [   36.183770]  mipi_dsi_device_transfer+0x44/0x58
> [   36.183781]  mipi_dsi_dcs_set_display_off_multi+0x9c/0xc4
> [   36.183792]  ili9881c_unprepare+0x38/0x88
> [   36.183802]  drm_panel_unprepare+0xbc/0x108
> [   36.183814]  panel_bridge_atomic_post_disable+0x50/0x60
> [   36.183823]  drm_atomic_bridge_call_post_disable+0x24/0x4c
> [   36.183835]  drm_atomic_bridge_chain_post_disable+0xa8/0x100
> [   36.183845]  drm_atomic_helper_commit_modeset_disables+0x2fc/0x5f8
> [   36.183856]  drm_atomic_helper_commit_tail_rpm+0x24/0x7c
> [   36.183865]  commit_tail+0xa4/0x18c
> [   36.183874]  drm_atomic_helper_commit+0x17c/0x194
> [   36.183884]  drm_atomic_commit+0x8c/0xcc
> [   36.183892]  drm_atomic_helper_disable_all+0x200/0x210
> [   36.183901]  drm_atomic_helper_shutdown+0xa8/0x150
> [   36.183911]  rzg2l_du_shutdown+0x18/0x24
> [   36.183920]  platform_shutdown+0x24/0x34
> [   36.183931]  device_shutdown+0x128/0x284
> [   36.183938]  kernel_restart+0x44/0xa4
> [   36.183950]  __do_sys_reboot+0x178/0x270
> [   36.183959]  __arm64_sys_reboot+0x24/0x30
> [   36.183968]  invoke_syscall.constprop.0+0x50/0xe4
> [   36.183979]  do_el0_svc+0x40/0xc0
> [   36.183988]  el0_svc+0x3c/0x164
> [   36.183995]  el0t_64_sync_handler+0xa0/0xe4
> [   36.184002]  el0t_64_sync+0x198/0x19c
> [   36.184020] Kernel Offset: disabled
> [   36.184022] CPU features: 0x200000,00020001,4000c501,0400720b
> [   36.184028] Memory Limit: none
> [   36.495305] ---[ end Kernel panic - not syncing: Asynchronous SError Interrupt ]---
> 
> The problem is present since linux-6.18-rc1, but not in linux-6.17. I also confirm the bug is present in linux-6.19-rc4.
> 
> The bug seems to be happening in rzg2l_mipi_dsi_host_transfer().
> 
> After bisecting, here is the first bad commit:
> 
>      commit 56de5e305d4b ("clk: renesas: r9a07g044: Add MSTOP for RZ/G2L")
> 
> Reverting this change makes the bug disappear.
> 
> My limited understanding seems to indicate that the MIPI/DSI host may
> no longer be available/on when the panel tries to send MIPI/DSI
> commands in ili9881c_unprepare(), maybe because the MIPI/DSI clock has been stopped...
> 
> The exact same board with two other panels (jd9365da and st7703) doesn't have the bug.

Could you please provide the output of command:

cat /sys/kernel/debug/mstop

for both cases?

Also, could you please check if the following diff solves your problem:

diff --git a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c 
b/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
index 5edd45424562..62957632a96f 100644
--- a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
+++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
@@ -1282,6 +1282,10 @@ static ssize_t 
rzg2l_mipi_dsi_host_transfer(struct mipi_dsi_host *host,
                 value |= SQCH0DSC0AR_FMT_SHORT;
         }

+       ret = pm_runtime_resume_and_get(dsi->dev);
+       if (ret)
+               return ret;
+
         rzg2l_mipi_dsi_link_write(dsi, SQCH0DSC0AR, value);

         /*
@@ -1322,6 +1326,8 @@ static ssize_t rzg2l_mipi_dsi_host_transfer(struct 
mipi_dsi_host *host,
                         ret = packet.payload_length;
         }

+       pm_runtime_put(dsi->dev);
+
         return ret;
  }

Thank you,
Claudiu