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Message-Id: <20260108125134.6ce05fd214a217a37de9ed4b@hugovil.com>
Date: Thu, 8 Jan 2026 12:51:34 -0500
From: Hugo Villeneuve <hugo@...ovil.com>
To: Biju Das <biju.das.jz@...renesas.com>
Cc: Claudiu.Beznea <claudiu.beznea@...on.dev>,
"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
"linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
"linux-kernel@...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>, Chris Brandt
<Chris.Brandt@...esas.com>
Subject: Re: [BUG] drm/panel: ilitek-ili9881c: kernel panic on reboot
Hi Biju,
On Thu, 8 Jan 2026 16:44:37 +0000
Biju Das <biju.das.jz@...renesas.com> wrote:
> Hi Hugo Villeneuve,
>
> > -----Original Message-----
> > From: Hugo Villeneuve <hugo@...ovil.com>
> > Sent: 08 January 2026 15:53
> > 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.
>
> Pre-MSTOP case during reboot, without clk it is accessing registers)(mstop off always)
> it won't crash. But looks like you may have ignored timeout error from [1].
In case of a timeout error, it is not really ignored as the proper error
code -ETIMEDOUT will be returned by rzg2l_mipi_dsi_host_transfer() (see log below). The
hardware manual doesn't seem to properly explain how to deal with a
timeout (or I could not find it). Do you have any suggestion on how to
improve this?
>
> Post MSTOP case, if you access registers with mstop on, it will lead to crash.
>
> and the patch fixes crash.
>
> Basically, you are accessing link register after video is stopped with this panel.
> Looks like it is a fix for me.
Ok, like I said I am not an expert on this, but I was just
assuming that there was a better way to ensure that the mipi/dsi
interface was still active until the panel unprepare() function
could do its work. I was looking at some other drivers mipi/dsi
host_transfer() functions and did not see a similar
pm_runtime_resume_and_get() scheme, hence my confusion.
> Better check if there is any timeout error[1] with this patch. if not,
> It is proper fix.
The patch does fixes the kernel panic, but
doesn't allow the panel to be properly unprepared,
as I just noticed the timeout message:
[ 39.321153] ili9881c-dsi 10850000.dsi.0: sending DCS SET_DISPLAY_OFF failed: -110
In my case, for a reboot, this is not a problem, but it may be a problem for systems where it can be suspended (I assume)?
Thank you for your help with this.
Hugo.
>
> [1] https://elixir.bootlin.com/linux/v6.19-rc4/source/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c#L893
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