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>

diff --git a/sound/soc/omap/omap-mcbsp.c b/sound/soc/omap/omap-mcbsp.c
index c7eb9dd67f608c47ffa93a97c1824e3dae3c867b..fd99d89de6a854606357b50c44deeb43bcfb04ab 100644 (file)
--- a/sound/soc/omap/omap-mcbsp.c
+++ b/sound/soc/omap/omap-mcbsp.c
@@ -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;