[alsa-devel] [RFC PATCH] ASoC: wm8960: Use physical width for bclk
bclk is derived from sysclk with the help of bclk_divs. Anyhow, for S20_3LE format there is no bclk_divs that could be used to derive an exact bclk.
We can fix this by using storage size instead the exact number of bits of the sample when computing bclk.
With this approach we can play S20_3LE encoded files at the cost of some unused BCLK cycles for S20_3LE and S24_LE.
Signed-off-by: Daniel Baluta daniel.baluta@nxp.com --- sound/soc/codecs/wm8960.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/sound/soc/codecs/wm8960.c b/sound/soc/codecs/wm8960.c index e1429e3..18ca5fc 100644 --- a/sound/soc/codecs/wm8960.c +++ b/sound/soc/codecs/wm8960.c @@ -722,7 +722,8 @@ static int wm8960_hw_params(struct snd_pcm_substream *substream, bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK; int i;
- wm8960->bclk = snd_soc_params_to_bclk(params); + wm8960->bclk = params_physical_width(params) * + params_channels(params) * params_rate(params); if (params_channels(params) == 1) wm8960->bclk *= 2;
On Tue, Mar 14, 2017 at 06:57:02PM +0200, Daniel Baluta wrote:
bclk is derived from sysclk with the help of bclk_divs. Anyhow, for S20_3LE format there is no bclk_divs that could be used to derive an exact bclk.
We can fix this by using storage size instead the exact number of bits of the sample when computing bclk.
With this approach we can play S20_3LE encoded files at the cost of some unused BCLK cycles for S20_3LE and S24_LE.
Signed-off-by: Daniel Baluta daniel.baluta@nxp.com
sound/soc/codecs/wm8960.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/sound/soc/codecs/wm8960.c b/sound/soc/codecs/wm8960.c index e1429e3..18ca5fc 100644 --- a/sound/soc/codecs/wm8960.c +++ b/sound/soc/codecs/wm8960.c @@ -722,7 +722,8 @@ static int wm8960_hw_params(struct snd_pcm_substream *substream, bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK; int i;
- wm8960->bclk = snd_soc_params_to_bclk(params);
- wm8960->bclk = params_physical_width(params) *
params_channels(params) * params_rate(params);
Would quite like to see Mark's thoughts on this. Feels a bit to me (although I am not certain) like we are solving the problem in the wrong place, isn't this really setting the desired BCLK and then in wm8960_configure_clocking we should set the lowest BCLK we can that is greater than or equal to the desired.
Thanks, Charles
On Mi, 2017-03-15 at 09:19 +0000, Charles Keepax wrote:
On Tue, Mar 14, 2017 at 06:57:02PM +0200, Daniel Baluta wrote:
bclk is derived from sysclk with the help of bclk_divs. Anyhow, for S20_3LE format there is no bclk_divs that could be used to derive an exact bclk.
We can fix this by using storage size instead the exact number of bits of the sample when computing bclk.
With this approach we can play S20_3LE encoded files at the cost of some unused BCLK cycles for S20_3LE and S24_LE.
Signed-off-by: Daniel Baluta daniel.baluta@nxp.com
sound/soc/codecs/wm8960.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/sound/soc/codecs/wm8960.c b/sound/soc/codecs/wm8960.c index e1429e3..18ca5fc 100644 --- a/sound/soc/codecs/wm8960.c +++ b/sound/soc/codecs/wm8960.c @@ -722,7 +722,8 @@ static int wm8960_hw_params(struct snd_pcm_substream *substream, bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK; int i;
- wm8960->bclk = snd_soc_params_to_bclk(params);
- wm8960->bclk = params_physical_width(params) *
params_channels(params) * params_rate(params);if (params_channels(params) == 1) wm8960->bclk *= 2;
Would quite like to see Mark's thoughts on this. Feels a bit to me (although I am not certain) like we are solving the problem in the wrong place, isn't this really setting the desired BCLK and then in wm8960_configure_clocking we should set the lowest BCLK we can that is greater than or equal to the desired.
Is there any standard way of doing this in ASoC? Couldn't find any example where the bitclk is relaxed to lowest value greater than the desired one.
I have prepared some patches with this approach, you can look at them here:
http://pastebin.com/0xW0E82N%C2%A0- some refactoring of sysclk search http://pastebin.com/QRt1UT7Q%C2%A0- relax bitclk value
Daniel.
On Wed, Mar 15, 2017 at 09:19:01AM +0000, Charles Keepax wrote:
On Tue, Mar 14, 2017 at 06:57:02PM +0200, Daniel Baluta wrote:
- wm8960->bclk = snd_soc_params_to_bclk(params);
- wm8960->bclk = params_physical_width(params) *
params_channels(params) * params_rate(params);
Would quite like to see Mark's thoughts on this. Feels a bit to me (although I am not certain) like we are solving the problem in the wrong place, isn't this really setting the desired BCLK and then in wm8960_configure_clocking we should set the lowest BCLK we can that is greater than or equal to the desired.
Exactly, this is the wrong fix in the wrong place - if this is something we want to do we should be doing it in the shared functions so all CODECs get the same behaviour but really I think Charles' suggestion makes more sense.
On Wed, Mar 15, 2017 at 3:33 PM, Mark Brown broonie@kernel.org wrote:
On Wed, Mar 15, 2017 at 09:19:01AM +0000, Charles Keepax wrote:
On Tue, Mar 14, 2017 at 06:57:02PM +0200, Daniel Baluta wrote:
- wm8960->bclk = snd_soc_params_to_bclk(params);
- wm8960->bclk = params_physical_width(params) *
params_channels(params) * params_rate(params);Would quite like to see Mark's thoughts on this. Feels a bit to me (although I am not certain) like we are solving the problem in the wrong place, isn't this really setting the desired BCLK and then in wm8960_configure_clocking we should set the lowest BCLK we can that is greater than or equal to the desired.
Exactly, this is the wrong fix in the wrong place - if this is something we want to do we should be doing it in the shared functions so all CODECs get the same behaviour but really I think Charles' suggestion makes more sense.
I see your point. Thanks a lot for feedback.
I already have an implementation for Charles' suggestion. Will send the patches asap.
thanks, Daniel.
participants (4)
-
Charles Keepax -
Daniel Baluta -
Daniel Baluta -
Mark Brown