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Date: Mon, 28 Mar 2022 17:11:48 +0200 From: Amadeusz Sławiński <amadeuszx.slawinski@...ux.intel.com> To: Sameer Pujar <spujar@...dia.com>, broonie@...nel.org, lgirdwood@...il.com, robh+dt@...nel.org, krzk+dt@...nel.org, perex@...ex.cz, tiwai@...e.com, peter.ujfalusi@...ux.intel.com, pierre-louis.bossart@...ux.intel.com Cc: oder_chiou@...ltek.com, devicetree@...r.kernel.org, alsa-devel@...a-project.org, linux-kernel@...r.kernel.org, jonathanh@...dia.com, thierry.reding@...il.com, linux-tegra@...r.kernel.org Subject: Re: [RFC PATCH v2 4/6] ASoC: soc-pcm: tweak DPCM BE hw_param() call order On 3/28/2022 8:14 AM, Sameer Pujar wrote: > For DPCM links, the order of hw_param() call depends on the sequence of > BE connection to FE. It is possible that one BE link can provide clock > to another BE link. In such cases consumer BE DAI, to get the rate set > by provider BE DAI, can use the standard clock functions only if provider > has already set the appropriate rate during its hw_param() stage. Above sentence seems to suggest that consumer can set clock only after provider has started, but code in this patch seems to do it the other way around? > > Presently the order is fixed and does not depend on the provider and > consumer relationships. So the clock rates need to be known ahead of > hw_param() stage. > > This patch tweaks the hw_param() order by connecting the provider BEs > late to a FE. With this hw_param() calls for provider BEs happen first > and then followed by consumer BEs. The consumers can use the standard > clk_get_rate() function to get the rate of the clock they depend on. > I'm bit confused by " With this hw_param() calls for provider BEs happen first and then followed by consumer BEs. " Aren't consumers started first and provider second? Code and previous sentence "connecting the provider BEs late to a FE" confuse me. Overall I don't exactly understand correct order of events after reading commit message and patch... > Signed-off-by: Sameer Pujar <spujar@...dia.com> > --- > TODO: > * The FE link is not considered in this. For Tegra it is fine to > call hw_params() for FE at the end. But systems, which want to apply > this tweak for FE as well, have to extend this tweak to FE. > * Also only DPCM is considered here. If normal links require such > tweak, it needs to be extended. > > sound/soc/soc-pcm.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 59 insertions(+), 1 deletion(-) > > diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c > index 9a95468..5829514 100644 > --- a/sound/soc/soc-pcm.c > +++ b/sound/soc/soc-pcm.c > @@ -1442,6 +1442,29 @@ static int dpcm_prune_paths(struct snd_soc_pcm_runtime *fe, int stream, > return prune; > } > > +static bool defer_dpcm_be_connect(struct snd_soc_pcm_runtime *rtd) > +{ > + struct snd_soc_dai *dai; > + int i; > + > + if (!(rtd->dai_link->dai_fmt & SND_SOC_DAIFMT_FORMAT_MASK)) > + return false; > + > + if ((rtd->dai_link->dai_fmt & SND_SOC_DAIFMT_CLOCK_PROVIDER_MASK) == > + SND_SOC_DAIFMT_CBC_CFC) { > + > + for_each_rtd_cpu_dais(rtd, i, dai) { > + > + if (!snd_soc_dai_is_dummy(dai)) > + return true; > + } > + } > + > + return false; > +} > + > +#define MAX_CLK_PROVIDER_BE 10 Not sure about this define, it adds unnecessary limitation on max clock number, can't you just run same loop twice while checking defer_dpcm_be_connect() first time and !defer_dpcm_be_connect() second time? defer_dpcm_be_connect() function name may need a bit of adjustment (rtd_is_clock_consumer() maybe?), but it gets rid of the limit. or do something like following instead of copy pasting loop twice: rename original dpcm_add_paths() to _dpcm_add_paths() and add additional argument and check somewhere inline: static int dpcm_add_paths(struct snd_soc_pcm_runtime *fe, int stream, struct snd_soc_dapm_widget_list **list_, bool clock_consumer) { ... // with renamed defer_dpcm_be_connect if (clock_consumer ^ !rtd_is_clock_consumer()) continue; ... } static int dpcm_add_paths(struct snd_soc_pcm_runtime *fe, int stream, struct snd_soc_dapm_widget_list **list_) { int ret; /* start clock consumer BEs */ ret = _dpcm_add_paths(*fe, stream, **list_, true); if (ret) return ret; /* start clock provider BEs */ ret = _dpcm_add_paths(*fe, stream, **list_, false); return ret; } > + > static int dpcm_add_paths(struct snd_soc_pcm_runtime *fe, int stream, > struct snd_soc_dapm_widget_list **list_) > { > @@ -1449,7 +1472,8 @@ static int dpcm_add_paths(struct snd_soc_pcm_runtime *fe, int stream, > struct snd_soc_dapm_widget_list *list = *list_; > struct snd_soc_pcm_runtime *be; > struct snd_soc_dapm_widget *widget; > - int i, new = 0, err; > + struct snd_soc_pcm_runtime *prov[MAX_CLK_PROVIDER_BE]; > + int i, new = 0, err, count = 0; > > /* Create any new FE <--> BE connections */ > for_each_dapm_widgets(list, i, widget) { > @@ -1489,6 +1513,40 @@ static int dpcm_add_paths(struct snd_soc_pcm_runtime *fe, int stream, > (be->dpcm[stream].state != SND_SOC_DPCM_STATE_CLOSE)) > continue; > > + /* Connect clock provider BEs at the end */ > + if (defer_dpcm_be_connect(be)) { > + if (count >= MAX_CLK_PROVIDER_BE) { > + dev_err(fe->dev, "ASoC: too many clock provider BEs\n"); > + return -EINVAL; > + } > + > + prov[count++] = be; > + continue; > + } > + > + /* newly connected FE and BE */ > + err = dpcm_be_connect(fe, be, stream); > + if (err < 0) { > + dev_err(fe->dev, "ASoC: can't connect %s\n", > + widget->name); > + break; > + } else if (err == 0) /* already connected */ > + continue; > + > + /* new */ > + dpcm_set_be_update_state(be, stream, SND_SOC_DPCM_UPDATE_BE); > + new++; > + } > + > + /* > + * Now connect clock provider BEs. A late connection means, > + * these BE links appear first in the list maintained by FE > + * and hw_param() call for these happen first. Let's stick to ALSA terminology, hw_params() please, same in commit message. > + */ > + for (i = 0; i < count; i++) { > + > + be = prov[i]; > + > /* newly connected FE and BE */ > err = dpcm_be_connect(fe, be, stream); > if (err < 0) {
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