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Message-Id: <20260108105319.6bef21d3fc60b261792d07c6@hugovil.com>
Date: Thu, 8 Jan 2026 10:53:19 -0500
From: Hugo Villeneuve <hugo@...ovil.com>
To: Claudiu Beznea <claudiu.beznea@...on.dev>
Cc: dri-devel@...ts.freedesktop.org, linux-renesas-soc@...r.kernel.org,
 linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org, Claudiu Beznea
 <claudiu.beznea.uj@...renesas.com>, Neil Armstrong
 <neil.armstrong@...aro.org>, Jessica Zhang <jesszhan0024@...il.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
 <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Biju Das Biju Das
 <biju.das.jz@...renesas.com>, Chris Brandt <Chris.Brandt@...esas.com>
Subject: Re: [BUG] drm/panel: ilitek-ili9881c: kernel panic on reboot

Hi Claudiu,

On Thu, 8 Jan 2026 11:12:54 +0200
Claudiu Beznea <claudiu.beznea@...on.dev> wrote:

> 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?

Here it is for the panel which has the bug:

----------------------------------
                           MSTOP     
                     clk   -------------------------
clk_name             cnt   cnt   off   val    shared
--------             ----- ----- ----- ------ ------
gic                  1     1     0xb80 0x0   
ia55_clk             2     2     0xb70 0x0    ia55_pclk ia55_clk
ia55_pclk            1     2     0xb70 0x0    ia55_pclk ia55_clk
dmac_aclk            2     1     0xb80 0x0   
dmac_pclk            1     1     0xb80 0x0   
ostm0_pclk           0     0     0xb7c 0x10  
ostm1_pclk           1     1     0xb7c 0x0   
ostm2_pclk           1     1     0xb7c 0x0   
mtu_x_mck            0     0     0xb64 0x4   
gpt_pclk             1     1     0xb64 0x0   
poeg_a_clkp          0     0     0xb64 0x20  
poeg_b_clkp          0     0     0xb64 0x40  
poeg_c_clkp          0     0     0xb64 0x80  
poeg_d_clkp          0     0     0xb64 0x100 
wdt0_pclk            1     2     0xb7c 0x0    wdt0_pclk wdt0_clk
wdt0_clk             1     2     0xb7c 0x0    wdt0_pclk wdt0_clk
wdt1_pclk            0     0     0xb7c 0x8    wdt1_pclk wdt1_clk
wdt1_clk             0     0     0xb7c 0x8    wdt1_pclk wdt1_clk
spi_clk2             0     0     0xb64 0x2    spi_clk2 spi_clk
spi_clk              0     0     0xb64 0x2    spi_clk2 spi_clk
sdhi0_imclk          1     4     0xb6c 0x0    sdhi0_imclk sdhi0_imclk2 sdhi0_clk_hs sdhi0_aclk
sdhi0_imclk2         2     4     0xb6c 0x0    sdhi0_imclk sdhi0_imclk2 sdhi0_clk_hs sdhi0_aclk
sdhi0_clk_hs         1     4     0xb6c 0x0    sdhi0_imclk sdhi0_imclk2 sdhi0_clk_hs sdhi0_aclk
sdhi0_aclk           1     4     0xb6c 0x0    sdhi0_imclk sdhi0_imclk2 sdhi0_clk_hs sdhi0_aclk
sdhi1_imclk          0     0     0xb6c 0x2    sdhi1_imclk sdhi1_imclk2 sdhi1_clk_hs sdhi1_aclk
sdhi1_imclk2         0     0     0xb6c 0x2    sdhi1_imclk sdhi1_imclk2 sdhi1_clk_hs sdhi1_aclk
sdhi1_clk_hs         0     0     0xb6c 0x2    sdhi1_imclk sdhi1_imclk2 sdhi1_clk_hs sdhi1_aclk
sdhi1_aclk           0     0     0xb6c 0x2    sdhi1_imclk sdhi1_imclk2 sdhi1_clk_hs sdhi1_aclk
gpu_clk              1     1     0xb80 0x0   
cru_sysclk           0     0     0xb78 0x8    cru_sysclk cru_vclk cru_pclk cru_aclk
cru_vclk             0     0     0xb78 0x8    cru_sysclk cru_vclk cru_pclk cru_aclk
cru_pclk             0     0     0xb78 0x8    cru_sysclk cru_vclk cru_pclk cru_aclk
cru_aclk             0     0     0xb78 0x8    cru_sysclk cru_vclk cru_pclk cru_aclk
dsi_pll_clk          1     6     0xb78 0x0    dsi_pll_clk dsi_sys_clk dsi_aclk dsi_pclk dsi_vclk dsi_lpclk
dsi_sys_clk          1     6     0xb78 0x0    dsi_pll_clk dsi_sys_clk dsi_aclk dsi_pclk dsi_vclk dsi_lpclk
dsi_aclk             1     6     0xb78 0x0    dsi_pll_clk dsi_sys_clk dsi_aclk dsi_pclk dsi_vclk dsi_lpclk
dsi_pclk             1     6     0xb78 0x0    dsi_pll_clk dsi_sys_clk dsi_aclk dsi_pclk dsi_vclk dsi_lpclk
dsi_vclk             1     6     0xb78 0x0    dsi_pll_clk dsi_sys_clk dsi_aclk dsi_pclk dsi_vclk dsi_lpclk
dsi_lpclk            1     6     0xb78 0x0    dsi_pll_clk dsi_sys_clk dsi_aclk dsi_pclk dsi_vclk dsi_lpclk
lcdc_a               3     1     0xb78 0x0    lcdc_a lcdc_p
lcdc_p               3     1     0xb78 0x0    lcdc_a lcdc_p
lcdc_clk_d           3     1     0xb78 0x0   
ssi0_pclk            0     0     0xb64 0x400  ssi0_pclk ssi0_sfr
ssi0_sfr             0     0     0xb64 0x400  ssi0_pclk ssi0_sfr
ssi1_pclk            0     0     0xb64 0x800  ssi1_pclk ssi1_sfr
ssi1_sfr             0     0     0xb64 0x800  ssi1_pclk ssi1_sfr
ssi2_pclk            0     0     0xb64 0x1000 ssi2_pclk ssi2_sfr
ssi2_sfr             0     0     0xb64 0x1000 ssi2_pclk ssi2_sfr
ssi3_pclk            0     0     0xb64 0x2000 ssi3_pclk ssi3_sfr
ssi3_sfr             0     0     0xb64 0x2000 ssi3_pclk ssi3_sfr
usb0_host            3     1     0xb6c 0x0   
usb1_host            0     0     0xb6c 0x80  
usb0_func            1     1     0xb6c 0x0   
usb_pclk             5     1     0xb6c 0x0   
eth0_axi             0     0     0xb6c 0x4    eth0_axi eth0_chi
eth0_chi             0     0     0xb6c 0x4    eth0_axi eth0_chi
eth1_axi             0     0     0xb6c 0x8    eth1_axi eth1_chi
eth1_chi             0     0     0xb6c 0x8    eth1_axi eth1_chi
i2c0                 0     0     0xb68 0x400 
i2c1                 0     0     0xb68 0x800 
i2c2                 0     0     0xb68 0x1000
i2c3                 0     0     0xb68 0x2000
scif0                2     1     0xb68 0x0   
scif1                0     0     0xb68 0x4   
scif2                0     0     0xb68 0x8   
scif3                0     0     0xb68 0x10  
scif4                0     0     0xb68 0x20  
sci0                 0     0     0xb68 0x80  
sci1                 0     0     0xb68 0x100 
rspi0                0     0     0xb64 0x4000
rspi1                0     0     0xb64 0x8000
rspi2                0     0     0xb68 0x1   
canfd                0     0     0xb68 0x200 
gpio                 1     1     0xb70 0x0   
adc_adclk            0     0     0xb68 0x4000 adc_adclk adc_pclk
adc_pclk             0     0     0xb68 0x4000 adc_adclk adc_pclk
tsu_pclk             1     1     0xb68 0x0   
----------------------------------

I do not have acces to the other panels for the moment to run the same command.


> 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;
>   }

I confirm that it fixes the bug, altought I assume this is just for testing and is not the "proper" fix.

Thank you for looking into this.

Hugo.

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