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ASoC: OMAP: mcbsp: Fix CLKX and CLKR pinmux when used as inputs 

This patch fixes faulty behaviour in a setup where the input clock for the
SRG is fed through the CLKR/CLKX pin but the McBSP is configured to be
master (SND_SOC_DAIFMT_CBS_CFS). In that case of course CLKR/CLKX must
not be configured as output pin. Otherwise the input clock is messed up
horribly.

This patch makes it possible to use the CLKR/CLKX pin rather than CLKS to
inject a reference clock in setups where McBSP is master and not both
rx and tx are used. However for this to work it has to be ensured that
set_dai_sysclk() is called after set_dai_fmt().

This was tested on a beagleboard-xm using McBSP1 to drive a i2s DAC through
the tx lines (CLKX,FSX,DX). Using this patch the CLKR pin is used to inject
an external reference clock.

Signed-off-by: Thomas Niederprüm <niederp@physik.uni-kl.de>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Thomas Niederprüm 2015-02-21 18:11:29 +01:00 committed by Mark Brown
parent fb5ab7296a
commit 8af4baa708
1 changed files with 11 additions and 0 deletions
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11
sound/soc/omap/omap-mcbsp.c
View File

@ -530,8 +530,19 @@ static int omap_mcbsp_dai_set_dai_sysclk(struct snd_soc_dai *cpu_dai,
case OMAP_MCBSP_SYSCLK_CLKX_EXT:
regs->srgr2 |= CLKSM;
regs->pcr0 |= SCLKME;
/*
* If McBSP is master but yet the CLKX/CLKR pin drives the SRG,
* disable output on those pins. This enables to inject the
* reference clock through CLKX/CLKR. For this to work
* set_dai_sysclk() _needs_ to be called after set_dai_fmt().
*/
regs->pcr0 &= ~CLKXM;
break;
case OMAP_MCBSP_SYSCLK_CLKR_EXT:
regs->pcr0 |= SCLKME;
/* Disable ouput on CLKR pin in master mode */
regs->pcr0 &= ~CLKRM;
break;
default:
err = -ENODEV;