linux-kernel - [PATCH] ALSA: hda: Request driver probe from an async task

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Date:   Mon, 23 Apr 2018 14:05:52 +0200
From:   Paul Menzel <pmenzel+alsa-devel@...gen.mpg.de>
To:     Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: [PATCH] ALSA: hda: Request driver probe from an async task

From: Paul Menzel <pmenzel@...gen.mpg.de>
Date: Sat, 24 Mar 2018 09:28:43 +0100

On an ASRock E350M1, with Linux 4.17-rc1 according to `initcall_debug`
calling `azx_driver_init` takes sometimes more than a few milliseconds,
and up to 200 ms.

```
[    2.892598] calling  azx_driver_init+0x0/0xfe4 [snd_hda_intel] @ 218
[    2.943002] initcall azx_driver_init+0x0/0xfe4 [snd_hda_intel] 
returned 0 after 49195 usecs
```

Trying to execute the Linux kernel in less than 500 ms, this is quite a
hold-up, and therefore request the probe from an async task.

With this change, the test shows, that the function returns earlier.

```
[    3.254800] calling  azx_driver_init+0x0/0xfe4 [snd_hda_intel] @ 227
[    3.254887] initcall azx_driver_init+0x0/0xfe4 [snd_hda_intel] 
returned 0 after 66 usecs
```

The same behavior is visible on a Dell OptiPlex 7010. The longer times
seem to happen, when the module *e1000e* is probed during the same time.

Signed-off-by: Paul Menzel <pmenzel@...gen.mpg.de>
---
  sound/pci/hda/hda_intel.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index 6347256bc017..827834b9c07d 100644
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -2671,6 +2671,7 @@ static struct pci_driver azx_driver = {
  	.driver = {
  		.pm = AZX_PM_OPS,
  	},
+	.driver.probe_type = PROBE_PREFER_ASYNCHRONOUS,
  };

  module_pci_driver(azx_driver);
-- 
2.16.2


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