[alsa-devel] [PATCHv2] ASoC: omap-mcbsp: Do not attempt to change DAI sysclk if stream is active

[Péter Ujfalusi]

Hi Mark, Liam,

Could you pick this patch?
For some reason it was missed, it is not present in upstream.

Thank you,
Péter

On Friday 10 June 2011 15:17:25 Jarkko Nikula wrote:
> Attempt to change McBSP CLKS source while another stream is active is not
> safe after commit d135865 ("OMAP: McBSP: implement functional clock
> switching via clock framework") in 2.6.37.
> 
> CLKS parent clock switching using clock framework have to idle the McBSP
> before switching and then activate it again. This short break can cause a
> DMA transaction error to already running stream which halts and recovers
> only by closing and restarting the stream.
> 
> This goes more fatal after commit e2fa61d ("OMAP3: l3: Introduce
> l3-interconnect error handling driver") in 2.6.39 where l3 driver detects a
> severe timeout error and does BUG_ON().
> 
> Fix this by not changing any configuration in omap_mcbsp_dai_set_dai_sysclk
> if the McBSP is already active. This test should have been here just from
> the beginning anyway.
> 
> Signed-off-by: Jarkko Nikula <jhnikula at gmail.com>
> Cc: stable at kernel.org
> ---
> v2:
> - Returns -EBUSY from omap_mcbsp_dai_set_dai_sysclk if the input clock rate
>   doesn't match with another stream's configuration and 0 otherwise.
> 
> For 2.6.37 and onward.
> 
> This issue is valid to those machine drivers that use the McBSP as a DAI
> link master and are configuring the CLKS source (like
> sound/soc/omap/omap3pandora.c in mainline).
> ---
>  sound/soc/omap/omap-mcbsp.c |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)
> 
> diff --git a/sound/soc/omap/omap-mcbsp.c b/sound/soc/omap/omap-mcbsp.c
> index 07b7723..4b82290 100644
> --- a/sound/soc/omap/omap-mcbsp.c
> +++ b/sound/soc/omap/omap-mcbsp.c
> @@ -516,6 +516,12 @@ static int omap_mcbsp_dai_set_dai_sysclk(struct
> snd_soc_dai *cpu_dai, struct omap_mcbsp_reg_cfg *regs = &mcbsp_data->regs;
>  	int err = 0;
> 
> +	if (mcbsp_data->active)
> +		if (freq == mcbsp_data->in_freq)
> +			return 0;
> +		else
> +			return -EBUSY;
> +
>  	/* The McBSP signal muxing functions are only available on McBSP1 */
>  	if (clk_id == OMAP_MCBSP_CLKR_SRC_CLKR ||
>  	    clk_id == OMAP_MCBSP_CLKR_SRC_CLKX ||