Alsa-Devel Archive on lore.kernel.org
 help / color / Atom feed
From: Anssi Hannula <anssi.hannula@iki.fi>
To: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Fabio Estevam <fabio.estevam@freescale.com>,
	alsa-devel@alsa-project.org, dri-devel@lists.freedesktop.org,
	Mark Brown <broonie@kernel.org>, Yakir Yang <ykk@rock-chips.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [alsa-devel] [PATCH 12/13] drm: bridge/dw_hdmi-ahb-audio: add audio driver
Date: Sat, 09 May 2015 19:49:44 +0300
Message-ID: <554E3AA8.8060601@iki.fi> (raw)
In-Reply-To: <E1Yr1y8-0006lG-Mw@rmk-PC.arm.linux.org.uk>

Hi,

A couple of things I noticed below:

09.05.2015, 13:26, Russell King kirjoitti:
> Add ALSA based HDMI AHB audio driver for dw_hdmi.  The only buffer
> format supported by the hardware is its own special IEC958 based format,
> which is not compatible with any ALSA format.  To avoid doing too much
> data manipulation within the driver, we support only ALSAs IEC958 LE and
> 24-bit PCM formats for 2 to 6 channels, which we convert to its hardware
> format.
> 
> A more desirable solution would be to have this conversion in userspace,
> but ALSA does not appear to allow such transformations outside of
> libasound itself.
> 
> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
> ---
>  drivers/gpu/drm/bridge/Kconfig             |  10 +
>  drivers/gpu/drm/bridge/Makefile            |   1 +
>  drivers/gpu/drm/bridge/dw_hdmi-ahb-audio.c | 560 +++++++++++++++++++++++++++++
>  drivers/gpu/drm/bridge/dw_hdmi-ahb-audio.h |  13 +
>  drivers/gpu/drm/bridge/dw_hdmi.c           |  24 ++
>  drivers/gpu/drm/bridge/dw_hdmi.h           |   3 +
>  6 files changed, 611 insertions(+)
>  create mode 100644 drivers/gpu/drm/bridge/dw_hdmi-ahb-audio.c
>  create mode 100644 drivers/gpu/drm/bridge/dw_hdmi-ahb-audio.h
> 
[...]
> +static void dw_hdmi_create_cs(struct snd_dw_hdmi *dw,
> +	struct snd_pcm_runtime *runtime)
> +{
> +	u8 cs[4];
> +	unsigned ch, i, j;
> +
> +	snd_pcm_create_iec958_consumer(runtime, cs, sizeof(cs));


I think generally drivers have left the iec958 bits for userspace to
handle, i.e. via a "IEC958 Playback Default"
(SNDRV_CTL_NAME_IEC958("",PLAYBACK,DEFAULT)) mixer element, with
defaults coming from /usr/share/alsa/pcm/hdmi.conf...

Looking at the sound driver tree, now, though, they are already somewhat
inconsistent:

1. Most drivers: iec958 bits from userspace, except for hw-set bits.

2. Some drivers (e.g. ctxfi, fsl_spdif): Some bits such as rate set by
driver, but everything is also exposed to userspace.
At least in fsl_spdif case the driver sets the stuff in hw_params which
would then get overwritten by userspace (which sets them after hw_params).

3. Some drivers (e.g. omap-hdmi-audio): Set by driver, not exposed to
userspace, like in this patch.

(Of course having userspace set them requires that the device has a
proper entry in /usr/share/alsa/cards and the pcm device is accessed via
the standard "hdmi" or "iec958" device names which perform the channel
status word setup. I guess the ARM SoC stuff generally doesn't bother
with that, explaining a bit why some kernel drivers set them by themselves).

The main interest to iec958 bits from userspace is probably towards the
non-audio bit, used for audio passthrough (the bit is not mandatory
there, but it helps).

Other drivers (well, I guess just HDA has this so far) also use the
userspace-provided non-audio bit to also select (in conjunction with
channels==8) the HBR mode, i.e. HD audio passthrough (which dw_hdmi also
supports via DMA_CONF0 but not enabled on this patch).


Since this isn't the first driver doing things this way, and this
doesn't really prevent exposing them to userspace later on, I guess this
patch is still OK here, unless the ALSA people think otherwise...


[...]
> +static struct snd_pcm_hardware dw_hdmi_hw = {
> +	.info = SNDRV_PCM_INFO_INTERLEAVED |
> +		SNDRV_PCM_INFO_BLOCK_TRANSFER |
> +		SNDRV_PCM_INFO_MMAP |
> +		SNDRV_PCM_INFO_MMAP_VALID,
> +	.formats = SNDRV_PCM_FMTBIT_IEC958_SUBFRAME_LE |
> +		   SNDRV_PCM_FMTBIT_S24_LE,
> +	.rates = SNDRV_PCM_RATE_32000 |
> +		 SNDRV_PCM_RATE_44100 |
> +		 SNDRV_PCM_RATE_48000 |
> +		 SNDRV_PCM_RATE_88200 |
> +		 SNDRV_PCM_RATE_96000 |
> +		 SNDRV_PCM_RATE_176400 |
> +		 SNDRV_PCM_RATE_192000,
> +	.channels_min = 2,
> +	.channels_max = 8,

You are providing multichannel support, but AFAICS you are not setting
the channel allocation (CA) bits in the audio infoframe anywhere
(HDMI_FC_AUDICONF2 register).

HDMI_FC_AUDICONF2 register default value is 0x00, which means plain
stereo (per CEA-861). If this is what goes on to the HDMI link as well,
the audio sink should ignore the other channels.
Did you check that multichannel PCM actually works? (maybe I'm just
missing where CA is set)


Note also that I think this HW uses the native HDMI channel order (from
CEA-861), which is different from the ALSA default channel order, so you
should inform userspace of the channel order (via
snd_pcm_add_chmap_ctls()). The channel order is specified by the CA
value I mentioned above.

Assuming I'm not missing something which makes everything work already,
one of these should be implemented:

(a) Provide all the chmaps (i.e. one per CA value) as a list for
userspace to select one, and provide the active chmap to userspace as well.

(b) Just hardcode a single CA value per channel count (which covers 99%
of use cases), and provide the corresponding active chmap to userspace.

(c) channels_max = 2.

Both (a) and (b) are generic stuff that could/should be in helpers for
all drivers to use (if (b), preferably with an interface that allows
easily extending it to (a) in the future).

Some of the code from sound/pci/hda/patch_hdmi.c should be useful (at
least the CA table it has - this stuff really shoud be outside the
driver). Note that much of the complexity of patch_hdmi.c comes from the
fact that the HW there supports channel remapping
(SNDRV_CTL_TLVT_CHMAP_VAR or _PAIRED), which dw_hdmi doesn't
(SNDRV_CTL_TLVT_CHMAP_FIXED).


-- 
-- 
Anssi Hannula
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/dri-devel

  reply index

Thread overview: 74+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-02  9:20 [RFC v2 0/13] dw_hdmi cleanups, audio preparation, helpers and ahb audio support Russell King - ARM Linux
2015-04-02  9:21 ` [PATCH RFC v2 01/13] drm: imx/dw_hdmi: move phy comments Russell King
2015-04-02  9:21 ` [PATCH RFC v2 02/13] drm: bridge/dw_hdmi: clean up phy configuration Russell King
2015-04-02  9:21 ` [PATCH RFC v2 03/13] drm: bridge/dw_hdmi: clean up hdmi_set_clk_regenerator() Russell King
2015-04-02  9:21 ` [PATCH RFC v2 04/13] drm: bridge/dw_hdmi: use drm_hdmi_avi_infoframe_from_display_mode() Russell King
2015-04-02  9:21 ` [PATCH RFC v2 05/13] drm: bridge/dw_hdmi: simplify hdmi_config_AVI() a little Russell King
2015-04-02  9:21 ` [PATCH RFC v2 06/13] drm: bridge/dw_hdmi: remove mhsyncpolarity/mvsyncpolarity/minterlaced Russell King
2015-04-02  9:21 ` [PATCH RFC v2 07/13] drm: bridge/dw_hdmi: introduce interface to setting sample rate Russell King
2015-04-02  9:21 ` [PATCH RFC v2 08/13] drm: bridge/dw_hdmi: introduce interfaces to enable and disable audio Russell King
2015-04-02  9:22 ` [PATCH RFC v2 09/13] drm/edid: add function to help find SADs Russell King
2015-04-02  9:22 ` [PATCH RFC v2 10/13] sound/core: add DRM ELD helper Russell King
2015-04-05 15:57   ` Takashi Iwai
2015-04-05 16:20     ` Russell King - ARM Linux
2015-04-05 16:46       ` Takashi Iwai
2015-04-05 17:26         ` Russell King - ARM Linux
2015-05-06 17:02           ` Anssi Hannula
2015-05-07 10:41             ` Russell King - ARM Linux
2015-05-07 11:11               ` Lars-Peter Clausen
2015-05-08 10:56           ` [alsa-devel] " Jyri Sarha
2015-05-08 11:42             ` Russell King - ARM Linux
2015-05-05 22:35     ` Mark Brown
2015-05-06  8:58       ` Liam Girdwood
2015-05-08 13:16   ` [alsa-devel] " Jyri Sarha
2015-05-08 13:27     ` Russell King - ARM Linux
2015-05-08 13:37       ` Jyri Sarha
2015-04-02  9:22 ` [PATCH RFC v2 11/13] sound/core: add IEC958 channel status helper Russell King
2015-04-02  9:22 ` [PATCH RFC v2 12/13] drm: bridge/dw_hdmi-ahb-audio: add audio driver Russell King
2015-04-02  9:22 ` [PATCH RFC v2 13/13] drm: bridge/dw_hdmi-ahb-audio: parse ELD from HDMI driver Russell King
2015-05-09 10:25 ` [PATCH v3 0/13] dw_hdmi cleanups, audio preparation, helpers and ahb audio support Russell King - ARM Linux
2015-05-09 10:25   ` [PATCH 01/13] drm: imx/dw_hdmi: move phy comments Russell King
2015-05-09 10:26   ` [PATCH 02/13] drm: bridge/dw_hdmi: clean up phy configuration Russell King
2015-05-22 15:19     ` Yakir
2015-05-09 10:26   ` [PATCH 03/13] drm: bridge/dw_hdmi: clean up hdmi_set_clk_regenerator() Russell King
2015-05-22 15:22     ` Yakir
2015-05-09 10:26   ` [PATCH 04/13] drm: bridge/dw_hdmi: use drm_hdmi_avi_infoframe_from_display_mode() Russell King
2015-05-09 10:26   ` [PATCH 05/13] drm: bridge/dw_hdmi: simplify hdmi_config_AVI() a little Russell King
2015-05-09 10:26   ` [PATCH 06/13] drm: bridge/dw_hdmi: remove mhsyncpolarity/mvsyncpolarity/minterlaced Russell King
2015-05-09 10:26   ` [PATCH 07/13] drm: bridge/dw_hdmi: introduce interface to setting sample rate Russell King
2015-05-22 15:26     ` Yakir
2015-05-09 10:26   ` [PATCH 08/13] drm: bridge/dw_hdmi: introduce interfaces to enable and disable audio Russell King
2015-05-22 15:28     ` Yakir
2015-05-09 10:26   ` [PATCH 09/13] drm/edid: add function to help find SADs Russell King
2015-05-09 10:26   ` [PATCH 10/13] sound/core: add DRM ELD helper Russell King
2015-05-22 12:20     ` [alsa-devel] " Mark Brown
2015-05-22 13:15       ` Russell King - ARM Linux
2015-05-22 13:30         ` Takashi Iwai
2015-05-22 13:53           ` Russell King - ARM Linux
2015-05-22 13:54             ` Takashi Iwai
2015-05-22 14:00               ` Russell King - ARM Linux
2015-05-22 14:02                 ` Takashi Iwai
2015-05-22 14:05                   ` Takashi Iwai
2015-05-22 16:12                     ` Russell King - ARM Linux
2015-05-09 10:26   ` [PATCH 11/13] sound/core: add IEC958 channel status helper Russell King
2015-05-22 12:40     ` Mark Brown
2015-05-09 10:26   ` [PATCH 12/13] drm: bridge/dw_hdmi-ahb-audio: add audio driver Russell King
2015-05-09 16:49     ` Anssi Hannula [this message]
2015-05-09 16:55       ` [alsa-devel] " Russell King - ARM Linux
2015-05-09 17:07         ` Anssi Hannula
2015-05-09 17:40           ` Russell King - ARM Linux
2015-05-09 17:53             ` Russell King - ARM Linux
2015-05-09 17:55             ` Anssi Hannula
2015-05-09 18:11               ` Russell King - ARM Linux
2015-05-10 18:59                 ` Anssi Hannula
2015-05-10 19:33                   ` Russell King - ARM Linux
2015-05-10 20:47                     ` Anssi Hannula
2015-05-11 15:58                     ` Mark Brown
2015-05-09 10:26   ` [PATCH 13/13] drm: bridge/dw_hdmi-ahb-audio: parse ELD from HDMI driver Russell King
2015-05-27 10:43     ` Daniel Vetter
2015-05-27 11:43       ` Mark Brown
2015-05-27 17:31       ` Russell King - ARM Linux
2015-05-27 21:29         ` Daniel Vetter
2015-05-27 21:44           ` Russell King - ARM Linux
2015-05-28  6:43             ` Daniel Vetter
2015-05-28  4:56         ` [alsa-devel] " Takashi Iwai

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=554E3AA8.8060601@iki.fi \
    --to=anssi.hannula@iki.fi \
    --cc=alsa-devel@alsa-project.org \
    --cc=broonie@kernel.org \
    --cc=dri-devel@lists.freedesktop.org \
    --cc=fabio.estevam@freescale.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=rmk+kernel@arm.linux.org.uk \
    --cc=ykk@rock-chips.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Alsa-Devel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/alsa-devel/0 alsa-devel/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 alsa-devel alsa-devel/ https://lore.kernel.org/alsa-devel \
		alsa-devel@alsa-project.org
	public-inbox-index alsa-devel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.alsa-project.alsa-devel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git