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Wang" Subject: Re: [EXT] Re: Suspend/resume Issue on pcm_dmix.c in alsa-lib In-Reply-To: References: <87msky1bqh.wl-tiwai@suse.de> <877cbrkafv.wl-tiwai@suse.de> <87ed5yh66b.wl-tiwai@suse.de> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/27.2 Mule/6.0 MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=ISO-2022-JP X-Spamd-Result: default: False [-3.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; TO_DN_SOME(0.00)[]; TO_DN_EQ_ADDR_SOME(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid,imap1.dmz-prg2.suse.org:helo] Message-ID-Hash: OHHF3AF4HGMVN6OWNN5CKVFTBOBZZ5RJ X-Message-ID-Hash: OHHF3AF4HGMVN6OWNN5CKVFTBOBZZ5RJ X-MailFrom: tiwai@suse.de X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-alsa-devel.alsa-project.org-0; header-match-alsa-devel.alsa-project.org-1; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.9 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Thu, 05 Sep 2024 13:01:11 +0200, Chancel Liu wrote: > > > > > > Hi Takashi, > > > > > > > > > > Thanks for your reply and suggestions. Finally we have found the root > > cause. > > > > > Seems it's related to both drivers and alsa-lib. > > > > > > > > > > When two dmix clients run in parallel we get two direct dmix instances. > > > > > 1st dmix instance: > > > > > snd_pcm_dmix_open() > > > > > snd_pcm_direct_initialize_slave() > > > > > save_slave_setting() > > > > > Since the driver we are using has SND_PCM_INFO_RESUME flag, > > > > > dmix->spcm->info has this flag. Then this flag is cleared in > > > > dmix->shmptr->s.info. > > > > > > > > > > 2nd dmix instance: > > > > > snd_pcm_dmix_open() > > > > > snd_pcm_direct_open_secondary_client() > > > > > copy_slave_setting() > > > > > 2nd dmix->spcm->info is copied from dmix->shmptr->s.info so it doesn' > > > > > has this flag. > > > > > > > > > > If 1st dmix instance resumes firstly it should implement recovery of > > > > > slave pcm in snd_pcm_direct_slave_recover(). Because 1st > > > > > dmix->spcm->info has > > > > > SND_PCM_INFO_RESUME，snd_pcm_resume(direct->spcm) can be called > > > > > correctly to resume slave pcm. > > > > > > > > ... and immediately stop the stream, then prepare and restart as a usual > > > > restart. > > > > > > > > > However if 2nd dmix instance resumes firstly, > > > > > snd_pcm_resume(direct->spcm) will not be called because it's > > > > > spcm->info doesn't has SND_PCM_INFO_RESUME flag. The 1st dmix > > instance > > > > > assumes someone else already did recovery so > > > > > snd_pcm_resume(direct->spcm) won't be called neither. In result the > > > > > slave pcm fails to resume. > > > > > > > > Something wrong happening here, then. > > > > > > > > In dmix, there is no hardware resume at all, but it's always a restart of the > > > > stream. The call of snd_pcm_resume() is only temporarily for > > inconsistencies > > > > that can be a problem on some drivers (IIRC dmaengine stuff). That said, > > > > dmix does a kind of fake resume, stops and restarts the stream cleanly on > > the > > > > first instance. On the second instance, it's already recovered, hence it > > bails > > > > out. > > > > > > > > If poll() hangs on the second instance, there can be some other problem. > > > > Maybe the resume -> stop -> restart sequence doesn't work with your > > driver > > > > well? > > > > > > > > > > Our dma driver will do PAUSE in system suspend and requires doing RESUME > > in > > > system resume. Current problem is that snd_pcm_resume() is not called by > > both > > > 1st instance and 2nd instance. > > > > That's weird. Are you really testing with the latest alsa-lib code? > > > > If application doesn't call snd_pcm_resume(), it means that the PCM > > state isn't set to SUSPENDED, so it pretends as if still running. > > > > Or if you mean that snd_pcm_resume() to the slave PCM isn't called > > (even though snd_pcm_resume() is called for the dmix PCM), check > > whether snd_pcm_direct_slave_recover() gets called, especially at the > > point: > > > > /* some buggy drivers require the device resumed before prepared; > > * when a device has RESUME flag and is in SUSPENDED state, > > resume > > * here but immediately drop to bring it to a sane active state. > > */ > > if (state == SND_PCM_STATE_SUSPENDED && > > (direct->spcm->info & SND_PCM_INFO_RESUME)) { > > snd_pcm_resume(direct->spcm); > > snd_pcm_drop(direct->spcm); > > snd_pcm_direct_timer_stop(direct); > > snd_pcm_direct_clear_timer_queue(direct); > > } > > > > Try to put debug prints or catch via breakpoint whether this code path > > is executed. > > > > Also, does the issue happen with the latest 6.11-rc kernel, too? > > If yes, what if you drop SNDRV_PCM_INFO_RESUME bit flag in the driver > > side? Does the problem persist, or it works? > > > > I'm working on kernel 6.6 and alsa-lib v1.2.11. It's not so outdated I think and > then I will try to switch on the latest version. > > Indeed I did some debug on this part. Please see my comments inline. > > int snd_pcm_direct_slave_recover(snd_pcm_direct_t *direct) > { > ... > > /* [Chancel] > * When two dmix clients run in parallel we get two direct dmix instances. > * 1st dmix->spcm->info has SND_PCM_INFO_RESUME flag but 2nd dmix doesn't. OK, that must be the cause. It's because the second open copies the saved shmem->s.info into spcm->info at its open time while we already dropped the INFO_RESUME bit. All the rest behavior are side effect of this inconsistency. I guess dropping the INFO_RESUME bit at hw_params and hw_refine should work instead. A totally untested fix is below. (And I believe the drop of INFO_PAUSE should be handled similarly, too, instead of dropping spcm->info bit there.) Takashi --- a/src/pcm/pcm_direct.c +++ b/src/pcm/pcm_direct.c @@ -1018,6 +1018,7 @@ int snd_pcm_direct_hw_refine(snd_pcm_t *pcm, snd_pcm_hw_params_t *params) } dshare->timer_ticks = hw_param_interval(params, SND_PCM_HW_PARAM_PERIOD_SIZE)->max / dshare->slave_period_size; params->info = dshare->shmptr->s.info; + params->info &= ~SND_PCM_INFO_RESUME; #ifdef REFINE_DEBUG snd_output_puts(log, "DMIX REFINE (end):\n"); snd_pcm_hw_params_dump(params, log); @@ -1031,6 +1032,7 @@ int snd_pcm_direct_hw_params(snd_pcm_t *pcm, snd_pcm_hw_params_t * params) snd_pcm_direct_t *dmix = pcm->private_data; params->info = dmix->shmptr->s.info; + params->info &= ~SND_PCM_INFO_RESUME; params->rate_num = dmix->shmptr->s.rate; params->rate_den = 1; params->fifo_size = 0; @@ -1183,8 +1185,6 @@ static void save_slave_setting(snd_pcm_direct_t *dmix, snd_pcm_t *spcm) COPY_SLAVE(buffer_time); COPY_SLAVE(sample_bits); COPY_SLAVE(frame_bits); - - dmix->shmptr->s.info &= ~SND_PCM_INFO_RESUME; } #undef COPY_SLAVE