At Tue, 02 Apr 2013 14:49:40 +0200, David Henningsson wrote: > > On 04/02/2013 02:18 PM, Takashi Iwai wrote: > > At Tue, 02 Apr 2013 13:53:16 +0200, > > David Henningsson wrote: > >> > >> On 03/27/2013 11:01 AM, Lin, Mengdong wrote: > >>>> -----Original Message----- > >>>> From: David Henningsson [mailto:david.henningsson@xxxxxxxxxxxxx] > >>>> Sent: Wednesday, March 27, 2013 4:19 PM > >>> > >>>>> The Haswell codec set_power_state ops (intel_haswell_set_power_state) will > >>>> only wait if this is a delayed resume and clear this flag after waiting. And > >>>> actually, there is no waiting even in this case. Because when 1st user operation > >>>> after system resume happens, Gfx already finishes resuming and audio > >>>> initialization, so as long as intel_haswell_wait_ready_to_resume() enable the > >>>> unsol event, the unsol event comes and so so waiting finishes. The 300ms time > >>>> out is set for safety consideration in case unsol event is lost. I've not observed > >>>> any unsol event lost till now. > >>>> > >>>> As for the timeout, I suggest you use the codec->bus->workq instead of > >>>> creating a new workq. I think that will also give us some serialisation, i e, > >>>> protection against race conditions if the timeout happen at the same time as > >>>> the unsol event. > >>> > >>> Hi David, > >>> > >>> The new added "resume_wq" for hdmi codec is a wait queue, not a work queue like codec->bus->workq. > >>> It's expected to wake up as soon as the unsol event is got. > >> > >> Sure; but I don't see why you need a wait queue for that? Why don't you > >> just call the resume path from the unsol event handler > >> (hdmi_present_sense, or its caller), and then also cancel the timeout > >> handler (which can then be in the normal workq)? > > > > Because the delayed resume actually fakes as if the resume is done. > > This is necessary not to block other device's resume operation. > > > > Since it looks as if ready, user-space might restart things soon again > > before the delayed resume is really finished. So, some serialization > > is required there. > > Lin, would it be possible to add some chain of events description to the > bug commit? The different contexts are just boggling my mind :-) Yeah, a nice code flow picture would be helpful :) > Assume we have two cases, system idle after S3 and immediate playback > after S3. > > Is this correct: > > System idle: > 1. System skips hda_call_codec_resume and sets codec->resume_delayed. > 2. Since the codec is not reinitialized, nothing powers up the codec, > so this is all that happens. > 3. Since unsol events are not enabled (?), we have a bug that jack > detection does not work and cannot be detected from userspace...? > > Immediate playback: > 1. System skips hda_call_codec_resume and sets codec->resume_delayed. > 2. Process context wants to start playback, which powers up the codec > and calls intel_haswell_set_power_state. > 3. intel_haswell_wait_ready_to_resume enables unsol events and starts > to wait on ready_to_resume > 4. Gfx init finishes, and workq context fires the unsol event, which > calls hdmi_intrinsic_event, which triggers the resume_wq. > 5. Process context and workq context now continues in parallel, > potentially (but hopefully not) leading to race conditions? The current patch has a small race, but it can be avoided by clearing spec->ready_to_resume early enough, e.g. in suspend callback or in init callback, like the patch below. Takashi --- diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c index 67e11ba..d0eafee 100644 --- a/sound/pci/hda/patch_hdmi.c +++ b/sound/pci/hda/patch_hdmi.c @@ -1740,6 +1740,9 @@ static int generic_hdmi_init(struct hda_codec *codec) hdmi_init_pin(codec, pin_nid); snd_hda_jack_detect_enable(codec, pin_nid, pin_nid); } + + spec->ready_to_resume = 0; + return 0; } @@ -1876,8 +1879,6 @@ static void intel_haswell_wait_ready_to_resume(struct hda_codec *codec) struct hdmi_spec *spec = codec->spec; int pin_idx; - spec->ready_to_resume = 0; - for (pin_idx = 0; pin_idx < spec->num_pins; pin_idx++) { struct hdmi_spec_per_pin *per_pin; hda_nid_t pin_nid; _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
