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Subject: Re: [PATCH] ASoC: meson: cards: deal dpcm flag change
To:     Jerome Brunet <jbrunet@baylibre.com>,
        Mark Brown <broonie@kernel.org>,
        Liam Girdwood <lgirdwood@gmail.com>
Cc:     alsa-devel@alsa-project.org, Kevin Hilman <khilman@baylibre.com>,
        linux-kernel@vger.kernel.org, zhangn1985@outlook.com,
        linux-amlogic@lists.infradead.org
From:   Marek Szyprowski <m.szyprowski@samsung.com>
Message-ID: <e950898e-0a07-4f75-2640-ec8039d81464@samsung.com>
Date:   Thu, 27 Aug 2020 14:43:06 +0200
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Hi Jerome,

On 31.07.2020 14:06, Jerome Brunet wrote:
> Commit b73287f0b074 ("ASoC: soc-pcm: dpcm: fix playback/capture checks")
> changed the meaning of dpcm_playback/dpcm_capture and now requires the
> CPU DAI BE to aligned with those flags.
>
> This broke all Amlogic cards with uni-directional backends (All gx and
> most axg cards).
>
> While I'm still confused as to how this change is an improvement, those
> cards can't remain broken forever. Hopefully, next time an API change is
> done like that, all the users will be updated as part of the change, and
> not left to fend for themselves.
>
> Fixes: b73287f0b074 ("ASoC: soc-pcm: dpcm: fix playback/capture checks")
> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>

This patch landed finally in v5.9-rc1. I've noticed it causes a 
following warning on Hardkernel's Odroid N2 board 
(arch/arm64/boot/dts/amlogic/meson-g12b-odroid-n2.dtb):

meson-drm ff900000.vpu: [drm] fb0: mesondrmfb frame buffer device
------------[ cut here ]------------
WARNING: CPU: 3 PID: 66 at sound/soc/soc-core.c:817 
snd_soc_find_dai+0xe4/0xf0
Modules linked in: dw_hdmi_i2s_audio dw_hdmi_cec meson_gxl realtek 
dwmac_generic crct10dif_ce snd_soc_meson_axg_sound_card 
snd_soc_meson_card_utils rc_odroid pwm_meson meson_ir 
snd_soc_meson_g12a_toacodec snd_soc_meson_axg_tdmout rtc_meson_vrtc 
snd_soc_meson_g12a_tohdmitx snd_soc_meson_codec_glue mdio_mux_meson_g12a 
snd_soc_meson_axg_tdmin dwmac_meson8b stmmac_platform 
reset_meson_audio_arb snd_soc_meson_axg_frddr axg_audio 
snd_soc_meson_axg_toddr sclk_div clk_phase meson_rng stmmac rng_core 
meson_dw_hdmi snd_soc_meson_axg_fifo meson_drm meson_canvas mdio_xpcs 
dw_hdmi snd_soc_meson_t9015 display_connector nvmem_meson_efuse 
snd_soc_meson_axg_tdm_interface snd_soc_meson_axg_tdm_formatter 
snd_soc_simple_amplifier
CPU: 3 PID: 66 Comm: kworker/3:1 Not tainted 5.9.0-rc1 #1527
Hardware name: Hardkernel ODROID-N2 (DT)
Workqueue: events deferred_probe_work_func
pstate: 60000005 (nZCv daif -PAN -UAO BTYPE=--)
pc : snd_soc_find_dai+0xe4/0xf0
lr : snd_soc_find_dai+0xe0/0xf0
...
Call trace:
  snd_soc_find_dai+0xe4/0xf0
  snd_soc_dai_link_set_capabilities+0x68/0x160
  axg_card_add_link+0x188/0x5c4 [snd_soc_meson_axg_sound_card]
  meson_card_probe+0x1e0/0x960 [snd_soc_meson_card_utils]
  platform_drv_probe+0x50/0xa8
  really_probe+0x110/0x400
  driver_probe_device+0x54/0xb8
  __device_attach_driver+0x90/0xc0
  bus_for_each_drv+0x70/0xc8
  __device_attach+0xec/0x150
  device_initial_probe+0x10/0x18
  bus_probe_device+0x94/0xa0
  deferred_probe_work_func+0x70/0xa8
  process_one_work+0x2a8/0x718
  worker_thread+0x48/0x460
  kthread+0x134/0x160
  ret_from_fork+0x10/0x1c
irq event stamp: 269690
hardirqs last  enabled at (269689): [<ffff800010f6048c>] 
_raw_spin_unlock_irqrestore+0x7c/0x98
hardirqs last disabled at (269690): [<ffff800010025a68>] 
do_debug_exception+0x140/0x26c
softirqs last  enabled at (269318): [<ffff800010001654>] 
efi_header_end+0x654/0x6d4
softirqs last disabled at (269313): [<ffff80001008929c>] 
irq_exit+0x16c/0x178
---[ end trace 56a3ea4fa00c37c8 ]---
...
axg-sound-card sound: ASoC: no DMI vendor name!

The warning is repeated 10 times.

The bisect between v5.8-rc1 and v5.9-rc1 points to the commit 
c8f7dbdbaa15 ("Merge remote-tracking branch 'asoc/for-5.8' into 
asoc-linus"), which introduced a branch with this patch.

The commit with this patch is applied on the earlier kernel release 
(da3f23fde9d7 "ASoC: meson: cards: deal dpcm flag change" on top of 
v5.7-rc1) worked fine, so it looks that there is an interference with 
something merged later.

If I revert this patch on top of v5.9-rc1 or current linux-next, the 
warning is gone. Let me know how I can help debugging this issue.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland