At Fri, 16 Sep 2011 09:16:54 -0500, Timur Tabi wrote:
The .set_sysclk() function in ASoC codec drivers can be used to tell the driver what the frequency of master clock (mclk) is. Some codecs use a divider on this clock to determine the sample rate. The WM8776 is one such codec.
So instead of hard-coding a list of specific sample rates supported, these codec drivers can specify SNDRV_PCM_RATE_CONTINUOUS instead, clamping the range to the absolute limits of the hardware. Then the .hw_params() function can use the mclk rate to determine whether any requested rate is actually supported.
Although the WM8776 driver includes a .set_sysclk function, it was also hard-coding the list of supported sample rates. We change the hard-coded list to a range within the capabilities of the WM8776 itself.
It's not optimal from some aspects. Basically this should be resolved in hw_constraints, not in hw_params, so that the configurator can find the possible rates. Otherwise you have no idea what rate would be accepted.
Since a few other codecs need the similar constraint, it may make sense to have a common helper hw_constraint for such a case.
thanks,
Takashi
Signed-off-by: Timur Tabi timur@freescale.com
sound/soc/codecs/wm8776.c | 13 ++++++------- 1 files changed, 6 insertions(+), 7 deletions(-)
diff --git a/sound/soc/codecs/wm8776.c b/sound/soc/codecs/wm8776.c index ad6f0fa..ca8a593 100644 --- a/sound/soc/codecs/wm8776.c +++ b/sound/soc/codecs/wm8776.c @@ -321,11 +321,6 @@ static int wm8776_set_bias_level(struct snd_soc_codec *codec, return 0; }
-#define WM8776_RATES (SNDRV_PCM_RATE_32000 | SNDRV_PCM_RATE_44100 |\
SNDRV_PCM_RATE_48000 | SNDRV_PCM_RATE_88200 |\SNDRV_PCM_RATE_96000)#define WM8776_FORMATS (SNDRV_PCM_FMTBIT_S16_LE | SNDRV_PCM_FMTBIT_S20_3LE |\ SNDRV_PCM_FMTBIT_S24_LE | SNDRV_PCM_FMTBIT_S32_LE)
@@ -350,7 +345,9 @@ static struct snd_soc_dai_driver wm8776_dai[] = { .stream_name = "Playback", .channels_min = 2, .channels_max = 2,
.rates = WM8776_RATES,
.rates = SNDRV_PCM_RATE_CONTINUOUS,.rate_min = 32000,.rate_max = 192000, .formats = WM8776_FORMATS,@@ -362,7 +359,9 @@ static struct snd_soc_dai_driver wm8776_dai[] = { .stream_name = "Capture", .channels_min = 2, .channels_max = 2,
.rates = WM8776_RATES,
.rates = SNDRV_PCM_RATE_CONTINUOUS,.rate_min = 32000,.rate_max = 96000, .formats = WM8776_FORMATS,-- 1.7.3.4
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