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ASoC: renesas: msiof: Add note for The possibility of R/L opposite Capture

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This driver is assuming MSIOF is used as Clock/Frame Consumer Mode, and
there is a case that some Codec (= Clock/Frame Provider) might output
Clock/Frame before setup MSIOF.

And, MSIOF will capture data without checking SYNC signal Hi/Low (= R/L).

This means, if MSIOF RXE bit was set as 1 in case of SYNC signal was Hi
(= R) timing, it will start capture data since next SYNC low signal (= L).
Because Linux assumes sound data is lined up as R->L->R->L->..., the data
R/L might be opposite.

The only solution in this case is start CLK/SYNC *after* MSIOF settings,
but it depends when and how Codec driver start it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Tested-by: Yusuke Goda <yusuke.goda.sx@renesas.com>
Link: https://patch.msgid.link/875xd7yutm.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Kuninori Morimoto 2025-09-25 05:17:41 +00:00 committed by Mark Brown
parent dc7473e637
commit 8c363f61e5
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1 changed files with 19 additions and 0 deletions
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19
sound/soc/renesas/rcar/msiof.c
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@ -46,6 +46,25 @@
* Setup both direction (Playback/Capture) in the same time.
*/
/*
* [NOTE-R/L]
*
* The data of Captured might be R/L opposite.
*
* This driver is assuming MSIOF is used as Clock/Frame Consumer Mode, and there is a case that some
* Codec (= Clock/Frame Provider) might output Clock/Frame before setup MSIOF. It depends on Codec
* driver implementation.
*
* MSIOF will capture data without checking SYNC signal Hi/Low (= R/L).
*
* This means, if MSIOF RXE bit was set as 1 in case of SYNC signal was Hi (= R) timing, it will
* start capture data since next SYNC low singla (= L). Because Linux assumes sound data is lined
* up as R->L->R->L->..., the data R/L will be opposite.
*
* The only solution in this case is start CLK/SYNC *after* MSIOF settings, but it depends when and
* how Codec driver start it.
*/
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_dma.h>