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authorRaffaele Recalcati <raffaele.recalcati@bticino.it>2010-07-06 10:39:04 +0200
committerMark Brown <broonie@opensource.wolfsonmicro.com>2010-07-06 23:54:07 +0900
commitd9823ed9fa3126097dfd2bbce6dc33957c1be728 (patch)
treea929aead29f43232b408b182ce5a5e5e4c8654a0 /arch/arm/mach-davinci
parentec6375533748806a1a49dad7ce124cc02886854a (diff)
downloadop-kernel-dev-d9823ed9fa3126097dfd2bbce6dc33957c1be728.zip
op-kernel-dev-d9823ed9fa3126097dfd2bbce6dc33957c1be728.tar.gz
ASoC: DaVinci: More accurate continuous serial clock for McBSP (I2S)
i2s_accurate_sck switch can be used to have a better approximate sampling frequency. The clock is an externally visible bit clock and it is named i2s continuous serial clock (I2S_SCK). The trade off is between more accurate clock (fast clock) and less accurate clock (slow clock). The waveform will be not symmetric. Probably it is possible to get a better algorithm for calculating the divider, trying to keep a slower clock as possible. This patch has been developed against the http://git.kernel.org/pub/scm/linux/kernel/git/khilman/linux-davinci.git git tree and has been tested on bmx board (similar to dm365 evm, but using uda1345 as external audio codec). Signed-off-by: Raffaele Recalcati <raffaele.recalcati@bticino.it> Signed-off-by: Davide Bonfanti <davide.bonfanti@bticino.it> Acked-by: Liam Girdwood <lrg@slimlogic.co.uk> Acked-by: Sudhakar Rajashekhara <sudhakar.raj@ti.com> Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Diffstat (limited to 'arch/arm/mach-davinci')
-rw-r--r--arch/arm/mach-davinci/include/mach/asp.h33
1 files changed, 33 insertions, 0 deletions
diff --git a/arch/arm/mach-davinci/include/mach/asp.h b/arch/arm/mach-davinci/include/mach/asp.h
index 0847d21..b12c69e 100644
--- a/arch/arm/mach-davinci/include/mach/asp.h
+++ b/arch/arm/mach-davinci/include/mach/asp.h
@@ -73,6 +73,39 @@ struct snd_platform_data {
*/
int clk_input_pin;
+ /*
+ * This flag works when both clock and FS are outputs for the cpu
+ * and makes clock more accurate (FS is not symmetrical and the
+ * clock is very fast.
+ * The clock becoming faster is named
+ * i2s continuous serial clock (I2S_SCK) and it is an externally
+ * visible bit clock.
+ *
+ * first line : WordSelect
+ * second line : ContinuousSerialClock
+ * third line: SerialData
+ *
+ * SYMMETRICAL APPROACH:
+ * _______________________ LEFT
+ * _| RIGHT |______________________|
+ * _ _ _ _ _ _ _ _
+ * _| |_| |_ x16 _| |_| |_| |_| |_ x16 _| |_| |_
+ * _ _ _ _ _ _ _ _
+ * _/ \_/ \_ ... _/ \_/ \_/ \_/ \_ ... _/ \_/ \_
+ * \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/
+ *
+ * ACCURATE CLOCK APPROACH:
+ * ______________ LEFT
+ * _| RIGHT |_______________________________|
+ * _ _ _ _ _ _ _ _ _
+ * _| |_ x16 _| |_| |_ x16 _| |_| |_| |_| |_| |_| |
+ * _ _ _ _ dummy cycles
+ * _/ \_ ... _/ \_/ \_ ... _/ \__________________
+ * \_/ \_/ \_/ \_/
+ *
+ */
+ bool i2s_accurate_sck;
+
/* McASP specific fields */
int tdm_slots;
u8 op_mode;
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