Re: [REGRESSION] drm/tegra: hdmi: tegra_hdmi_setup_audio: division by zero in kernel

From: Dmitry Osipenko <digetx@gmail.com>
To: Marcel Ziswiler <marcel.ziswiler@toradex.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>
Cc: "treding@nvidia.com" <treding@nvidia.com>,
	"alban.bedel@avionic-design.de" <alban.bedel@avionic-design.de>
Subject: Re: [REGRESSION] drm/tegra: hdmi: tegra_hdmi_setup_audio: division by zero in kernel
Date: Sun, 10 Feb 2019 19:51:23 +0300	[thread overview]
Message-ID: <139085a2-014a-b666-2d3f-d1833b6017c5@gmail.com> (raw)
In-Reply-To: <87f8fd40b25e2842b547059a8d28295533e8c09c.camel@toradex.com>

08.02.2019 23:01, Marcel Ziswiler пишет:
> Hi there
> 
> I just stumbled over this one:
> 
> [   31.026220] Division by zero in kernel.
> [   31.026238] CPU: 1 PID: 529 Comm: X Not tainted 5.0.0-rc5-next-
> 20190208-dirty #153
> [   31.026244] Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
> [   31.026281] [<c01120cc>] (unwind_backtrace) from [<c010c92c>]
> (show_stack+0x10/0x14)
> [   31.026301] [<c010c92c>] (show_stack) from [<c0a7c5ac>]
> (dump_stack+0xb4/0xc8)
> [   31.026317] [<c0a7c5ac>] (dump_stack) from [<c0a7a7e4>]
> (Ldiv0+0x8/0x10)
> [   31.026337] [<c0a7a7e4>] (Ldiv0) from [<c0588758>]
> (tegra_hdmi_setup_audio+0x1ac/0xed0)
> [   31.026353] [<c0588758>] (tegra_hdmi_setup_audio) from [<c0589a68>]
> (tegra_hdmi_encoder_enable+0x5ec/0x2a20)
> [   31.026379] [<c0589a68>] (tegra_hdmi_encoder_enable) from
> [<c054415c>] (drm_atomic_helper_commit_modeset_enables+0x10c/0x220)
> [   31.026397] [<c054415c>] (drm_atomic_helper_commit_modeset_enables)
> from [<c054449c>] (drm_atomic_helper_commit_tail_rpm+0x24/0x6c)
> [   31.026412] [<c054449c>] (drm_atomic_helper_commit_tail_rpm) from
> [<c054431c>] (commit_tail+0x40/0x6c)
> [   31.026427] [<c054431c>] (commit_tail) from [<c054440c>]
> (drm_atomic_helper_commit+0xbc/0x128)
> [   31.026443] [<c054440c>] (drm_atomic_helper_commit) from
> [<c0547260>] (restore_fbdev_mode_atomic+0x160/0x1cc)
> [   31.026457] [<c0547260>] (restore_fbdev_mode_atomic) from
> [<c0547420>] (drm_fb_helper_pan_display+0xc4/0x1d0)
> [   31.026481] [<c0547420>] (drm_fb_helper_pan_display) from
> [<c04b0250>] (fb_pan_display+0x9c/0x118)
> [   31.026498] [<c04b0250>] (fb_pan_display) from [<c04b0fdc>]
> (do_fb_ioctl+0x4b0/0x7cc)
> [   31.026514] [<c04b0fdc>] (do_fb_ioctl) from [<c027e688>]
> (do_vfs_ioctl+0xac/0x8f8)
> [   31.026527] [<c027e688>] (do_vfs_ioctl) from [<c027ef08>]
> (ksys_ioctl+0x34/0x60)
> [   31.026540] [<c027ef08>] (ksys_ioctl) from [<c0101000>]
> (ret_fast_syscall+0x0/0x54)
> [   31.026546] Exception stack(0xcba59fa8 to 0xcba59ff0)
> [   31.026559] 9fa0:                   001527a8 00152278 0000000a
> 00004606 00152808 00000000
> [   31.026572] 9fc0: 001527a8 00152278 0015b368 00000036 b6f20961
> 0000000a bedb5dd4 00000000
> [   31.026581] 9fe0: b6af7098 bedb5b1c b6af4603 b6cdb67c
> [   31.026586] Division by zero in kernel.
> [   31.026595] CPU: 1 PID: 529 Comm: X Not tainted 5.0.0-rc5-next-
> 20190208-dirty #153
> [   31.026600] Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
> [   31.026615] [<c01120cc>] (unwind_backtrace) from [<c010c92c>]
> (show_stack+0x10/0x14)
> [   31.026629] [<c010c92c>] (show_stack) from [<c0a7c5ac>]
> (dump_stack+0xb4/0xc8)
> [   31.026640] [<c0a7c5ac>] (dump_stack) from [<c0a7a7e4>]
> (Ldiv0+0x8/0x10)
> [   31.026654] [<c0a7a7e4>] (Ldiv0) from [<c05887ac>]
> (tegra_hdmi_setup_audio+0x200/0xed0)
> [   31.026667] [<c05887ac>] (tegra_hdmi_setup_audio) from [<c0589a68>]
> (tegra_hdmi_encoder_enable+0x5ec/0x2a20)
> [   31.026684] [<c0589a68>] (tegra_hdmi_encoder_enable) from
> [<c054415c>] (drm_atomic_helper_commit_modeset_enables+0x10c/0x220)
> [   31.026700] [<c054415c>] (drm_atomic_helper_commit_modeset_enables)
> from [<c054449c>] (drm_atomic_helper_commit_tail_rpm+0x24/0x6c)
> [   31.026715] [<c054449c>] (drm_atomic_helper_commit_tail_rpm) from
> [<c054431c>] (commit_tail+0x40/0x6c)
> [   31.026729] [<c054431c>] (commit_tail) from [<c054440c>]
> (drm_atomic_helper_commit+0xbc/0x128)
> [   31.026743] [<c054440c>] (drm_atomic_helper_commit) from
> [<c0547260>] (restore_fbdev_mode_atomic+0x160/0x1cc)
> [   31.026755] [<c0547260>] (restore_fbdev_mode_atomic) from
> [<c0547420>] (drm_fb_helper_pan_display+0xc4/0x1d0)
> [   31.026770] [<c0547420>] (drm_fb_helper_pan_display) from
> [<c04b0250>] (fb_pan_display+0x9c/0x118)
> [   31.026785] [<c04b0250>] (fb_pan_display) from [<c04b0fdc>]
> (do_fb_ioctl+0x4b0/0x7cc)
> [   31.026797] [<c04b0fdc>] (do_fb_ioctl) from [<c027e688>]
> (do_vfs_ioctl+0xac/0x8f8)
> [   31.026809] [<c027e688>] (do_vfs_ioctl) from [<c027ef08>]
> (ksys_ioctl+0x34/0x60)
> [   31.026820] [<c027ef08>] (ksys_ioctl) from [<c0101000>]
> (ret_fast_syscall+0x0/0x54)
> [   31.026826] Exception stack(0xcba59fa8 to 0xcba59ff0)
> [   31.026837] 9fa0:                   001527a8 00152278 0000000a
> 00004606 00152808 00000000
> [   31.026850] 9fc0: 001527a8 00152278 0015b368 00000036 b6f20961
> 0000000a bedb5dd4 00000000
> [   31.026859] 9fe0: b6af7098 bedb5b1c b6af4603 b6cdb67c
> 
> This has been observed on a Apalis T30 2GB running todays -next.
> 
> Anybody knowing what is going on before I dig deeper?

Sounds like this [0] could be the cause.

[0] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/gpu/drm/tegra?id=db5adf4d6dced4e3326ce369fe0c213c968095f4

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