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Kuninori Morimoto <kuninori.morimoto.gx@renesas.com> says:
Current ASoC supports snd_soc_daifmt_parse_format() which can specify DAI
format by "dai-format" property from DT.
But strictly speaking, it is SW settings, so doesn't match to DT's policy.
Current ASoC is supporting auto format select via
snd_soc_dai_ops :: .auto_selectable_formats.
But the user is very few today.
DT doesn't need to specify the DAI format via "dai-format", if both CPU
and Codec drivers were supporting .auto_selectable_formats. It will be
automatically selected from .auto_selectable_formats.
But, I noticed that current auto format select method can't handle all cases.
For example, current .auto_selectable_formats is like below
static u64 xxx_auto_formats[] = {
(A) /* First Priority */
SND_SOC_POSSIBLE_DAIFMT_I2S |
SND_SOC_POSSIBLE_DAIFMT_LEFT_J |
SND_SOC_POSSIBLE_DAIFMT_NB_NF |
SND_SOC_POSSIBLE_DAIFMT_NB_IF | (x)
SND_SOC_POSSIBLE_DAIFMT_IB_NF |
SND_SOC_POSSIBLE_DAIFMT_IB_IF, (x)
/* Second Priority */
(B) SND_SOC_POSSIBLE_DAIFMT_DSP_A | (y)
SND_SOC_POSSIBLE_DAIFMT_DSP_B, (y)
};
It try to find DAI format from (A) first, and next it will use (A | B).
But it can't handle the format if some format were independent.
For example, DSP_x (y) can't use with xB_IF (x), etc.
So, I would like to update the method. New method doesn't use OR.
It try to find DAI format from (a), next it will use (b).
static u64 xxx_auto_formats[] = {
(a) /* First Priority */
SND_SOC_POSSIBLE_DAIFMT_I2S |
SND_SOC_POSSIBLE_DAIFMT_LEFT_J |
SND_SOC_POSSIBLE_DAIFMT_NB_NF |
SND_SOC_POSSIBLE_DAIFMT_NB_IF |
SND_SOC_POSSIBLE_DAIFMT_IB_NF |
SND_SOC_POSSIBLE_DAIFMT_IB_IF,
/* Second Priority */
(b) SND_SOC_POSSIBLE_DAIFMT_DSP_A |
SND_SOC_POSSIBLE_DAIFMT_DSP_B |
SND_SOC_POSSIBLE_DAIFMT_NB_NF |
SND_SOC_POSSIBLE_DAIFMT_IB_NF,
};
Switch old method to new method, Current auto select user need to update
.auto_selectable_formats. Fortunately, current few users doesn't have
above limitation. update (A)(B) to (a)(b) style is possible.
a = A
b = A | B
I would like to update method, and add .auto_selectable_formats
support on all drivers.
One note is that auto select might not find best format on some CPU/Codec
combination. So "dai-format" is necessary anyway.
And, there haven't been any big problems on .auto_selectable_formats,
because there were few users.
But if all drivers try to use this, it cannot be denied that they may
encounter unknown problems... In such case, "dai-format" can help, though.
Link: https://patch.msgid.link/87v7bs36m0.wl-kuninori.morimoto.gx@renesas.com
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