At Fri, 10 Jan 2014 19:59:42 +0800, Nenghua Cao wrote: > > On 01/10/2014 07:47 PM, Liam Girdwood wrote: > > On Fri, 2014-01-10 at 19:21 +0800, Nenghua Cao wrote: > >> On 01/10/2014 06:55 PM, Takashi Iwai wrote: > >>> [Corrected mail addresses of both Mark and Liam] > >>> > >> Hi, Takashi: > >> Thanks for correcting my mistake. > >>> At Fri, 10 Jan 2014 13:36:35 +0800, > >>> Nenghua Cao wrote: > >>>> > >>>> From: Nenghua Cao <nh...@marvell.com> > >>>> > >>>> It fixes the following case: > >>>> Two FEs connects the same BE; FE1 & BE path has been opened and > >>>> hw_paramed. > >>>> At this momment, FE2 & BE path is being opened and hw_paramed. The BE > >>>> dai will do hw_param again even if it has done hw_param. It is not > >>>> reasonable. > >>>> FE1------------>BE > >>>> FE2-------------^ > >>> > >>> What happens if FE2 tries to set up an incompatible hw_params? > >>> (Through a quick glance, it won't work properly well, too, though...) > >>> > > > > The intention in this case would be for the DSP FE driver to determine > > if it can perform format conversion or SRC to the running BE. If the DSP > > cant do the conversion then it should fail. > > > >> If FE2 uses an incompatible param, it will make FE1 doesn't work. Maybe > >> FE2 works well. > >> If FE2 uses the same param, BE hw_param function will be called twice > >> (This is the most happening case). > >> So we can't get benefits from it. > > > > We shouldn't be calling the hw_params() on the BE when it's already > > configured in this case. So this seems like a bug. However :- > > > > /* only allow hw_params() if no connected FEs are running */ > > if (!snd_soc_dpcm_can_be_params(fe, be, stream)) > > continue; > > > > if ((be->dpcm[stream].state != SND_SOC_DPCM_STATE_OPEN) && > > (be->dpcm[stream].state != SND_SOC_DPCM_STATE_HW_PARAMS) && > > (be->dpcm[stream].state != SND_SOC_DPCM_STATE_HW_FREE)) > > continue; > > > > We do do a test to check if any connected FEs are running (i.e. > > triggered) prior to calling hw_params() on the BE. Can you confirm if > > the FE was running in your case ? > > > Hi, Liam: > I am so glad to hear from you. In my case, FE1 has called hw_param, > and before FE1 calls prepare/trigger function, the scheduler switches to > do FE2 open, hw_param. So hw_param is called twice.
So basically the current implementation is racy about this. OTOH, not calling hw_params twice is also buggy. hw_params may be called multiple times without hw_free for the same stream if user wants to re-setup/update the parameters. OSS emulation layer does it, for example. Takashi > > > Thanks > > > > Liam > > > >>> > >>> Takashi > >>> > >>>> > >>>> Signed-off-by: Nenghua Cao <nh...@marvell.com> > >>>> --- > >>>> sound/soc/soc-pcm.c | 1 - > >>>> 1 files changed, 0 insertions(+), 1 deletions(-) > >>>> > >>>> diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c > >>>> index 891b9a9..ec07e37 100644 > >>>> --- a/sound/soc/soc-pcm.c > >>>> +++ b/sound/soc/soc-pcm.c > >>>> @@ -1339,7 +1339,6 @@ static int dpcm_be_dai_hw_params(struct > >>>> snd_soc_pcm_runtime *fe, int stream) > >>>> continue; > >>>> > >>>> if ((be->dpcm[stream].state != SND_SOC_DPCM_STATE_OPEN) > >>>> && > >>>> - (be->dpcm[stream].state != > >>>> SND_SOC_DPCM_STATE_HW_PARAMS) && > >>>> (be->dpcm[stream].state != > >>>> SND_SOC_DPCM_STATE_HW_FREE)) > >>>> continue; > >>>> > >>>> -- > >>>> 1.7.0.4 > >>>> > >>>> _______________________________________________ > >>>> Alsa-devel mailing list > >>>> alsa-de...@alsa-project.org > >>>> http://mailman.alsa-project.org/mailman/listinfo/alsa-devel > >>>> > >> > > > > > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
