Re: [RFC] i915: make the probe asynchronous

[Feng Tang <feng.tang@intel.com>]

On Thu, Jul 12, 2018 at 09:37:41AM +0200, Daniel Vetter wrote:
> On Thu, Jul 12, 2018 at 8:56 AM, Takashi Iwai <tiwai@suse.de> wrote:
> > On Thu, 12 Jul 2018 08:54:34 +0200,
> > Daniel Vetter wrote:
> >>
> >> On Thu, Jul 12, 2018 at 09:29:01AM +0800, Feng Tang wrote:
> >> > On Tue, Jun 26, 2018 at 10:29:16AM +0800, Feng Tang wrote:
> >> > > On Mon, Jun 25, 2018 at 05:36:32PM +0200, Daniel Vetter wrote:
> >> >
> >> > > Hi Daneil/Jani/Takashi,
> >> > >
> >> > > When I was testing this patch from Takashi, I further checked the kernel
> >> > > module code, and found that: we may need NOT to add any new codes to
> >> > > prepare for i915's async probe feature!
> >> > >
> >> > > Say when i915 module is being loader due to HDA's request_module() call,
> >> > > in the callchain, do_init_module() has such code:
> >> > >
> >> > >     if (!mod->async_probe_requested && (current->flags & PF_USED_ASYNC))
> >> > >                 async_synchronize_full();
> >> > >
> >> > > This will garantee the asynced probe is done before it returns.
> >> > >
> >> > > I have just tested and this seems to be enough. If I am not wrong, then
> >> > > we can take the i915 async patch directly. What do you think?
> >> >
> >> > Ping for comments, thanks!
> >>
> >> Ram (who's working on the hdcp2 code) just learned the hard way that if
> >> i915 registration gets delayed then audio fails to load. So if you want to
> >> make i915 fully async, then you _must_ fix the audio load stuff.
> >
> > Does my component completion patch help for that scenario?
> 
> Hm, must have missed it. Do you have a patchwork link?
> 
> Also adding Ram so he can test this out.

Here is Iwai's patch that I found in my inbox:

-----

--- a/sound/hda/hdac_i915.c
+++ b/sound/hda/hdac_i915.c
@@ -23,6 +23,7 @@
 #include <sound/hda_register.h>
 
 static struct i915_audio_component *hdac_acomp;
+static DECLARE_COMPLETION(acomp_bound);
 
 /**
  * snd_hdac_set_codec_wakeup - Enable / disable HDMI/DP codec wakeup
@@ -284,6 +285,7 @@ static int hdac_component_master_bind(struct device *dev)
 		goto out_unbind;
 	}
 
+	complete_all(&acomp_bound);
 	return 0;
 
 out_unbind:
@@ -382,11 +384,8 @@ int snd_hdac_i915_init(struct hdac_bus *bus)
 	if (ret < 0)
 		goto out_err;
 
-	/*
-	 * Atm, we don't support deferring the component binding, so make sure
-	 * i915 is loaded and that the binding successfully completes.
-	 */
 	request_module("i915");
+	wait_for_completion_timeout(&acomp_bound, 10000); /* 10s timeout */
 
 	if (!acomp->ops) {
 		ret = -ENODEV;
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