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Date: Wed, 28 Nov 2012 09:45:39 +0100
From: Takashi Iwai <tiwai@...e.de>
To: Daniel J Blueman <daniel@...ra.org>
Cc: Seth Forshee <seth.forshee@...onical.com>,
Dave Airlie <airlied@...ux.ie>,
Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: switcheroo registration vs switching race...
At Wed, 28 Nov 2012 11:45:07 +0800,
Daniel J Blueman wrote:
>
> Hi Seth, Dave, Takashi,
>
> If I power down the unused discrete GPU before lightdm starts by
> fiddling with the sysfs file [1] in the upstart script, I see a race
> manifesting as the discrete GPU's HDA controller timing out to
> commands [2].
>
> Adding some debug, I see that the registered audio devices are put
> into D3 before the GPU is, but it turns out that the discrete (and
> internal) GPU's HDA controller gets registered a bit later, so the
> list is empty. The symptom is since the HDA driver it's talking to
> hardware which is now in D3.
>
> We could add a mutex to nouveau to allow us to wait for the DGPU HDA
> controller, but perhaps this should be solved at a higher level in the
> vgaswitcheroo code; what do you think?
Maybe it's a side effect for the recent effort to fix another race in
the probe. A part of them problem is that the registration is done at
the very last of probing.
Instead of delaying the registration, how about the patch below?
Takashi
---
diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index 4bb52da..17fbd68 100644
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -49,6 +49,7 @@
#include <linux/pm_runtime.h>
#include <linux/clocksource.h>
#include <linux/time.h>
+#include <linux/completion.h>
#ifdef CONFIG_X86
/* for snoop control */
@@ -469,6 +470,7 @@ struct azx {
/* locks */
spinlock_t reg_lock;
struct mutex open_mutex;
+ struct completion probe_wait;
/* streams (x num_streams) */
struct azx_dev *azx_dev;
@@ -2790,6 +2792,7 @@ static bool azx_vs_can_switch(struct pci_dev *pci)
struct snd_card *card = pci_get_drvdata(pci);
struct azx *chip = card->private_data;
+ wait_for_completion(&chip->probe_wait);
if (chip->init_failed)
return false;
if (chip->disabled || !chip->bus)
@@ -2851,6 +2854,9 @@ static int azx_free(struct azx *chip)
azx_notifier_unregister(chip);
+ chip->init_failed = 1; /* to be sure */
+ complete(&chip->probe_wait);
+
if (use_vga_switcheroo(chip)) {
if (chip->disabled && chip->bus)
snd_hda_unlock_devices(chip->bus);
@@ -3156,6 +3162,7 @@ static int __devinit azx_create(struct snd_card *card, struct pci_dev *pci,
INIT_LIST_HEAD(&chip->pcm_list);
INIT_LIST_HEAD(&chip->list);
init_vga_switcheroo(chip);
+ init_completion(&chip->probe_wait);
chip->position_fix[0] = chip->position_fix[1] =
check_position_fix(chip, position_fix[dev]);
@@ -3462,6 +3469,13 @@ static int __devinit azx_probe(struct pci_dev *pci,
}
#endif /* CONFIG_SND_HDA_PATCH_LOADER */
+ err = register_vga_switcheroo(chip);
+ if (err < 0) {
+ snd_printk(KERN_ERR SFX
+ "Error registering VGA-switcheroo client\n");
+ goto out_free;
+ }
+
if (probe_now) {
err = azx_probe_continue(chip);
if (err < 0)
@@ -3473,14 +3487,8 @@ static int __devinit azx_probe(struct pci_dev *pci,
if (pci_dev_run_wake(pci))
pm_runtime_put_noidle(&pci->dev);
- err = register_vga_switcheroo(chip);
- if (err < 0) {
- snd_printk(KERN_ERR SFX
- "Error registering VGA-switcheroo client\n");
- goto out_free;
- }
-
dev++;
+ complete(&chip->probe_wait);
return 0;
out_free:
--
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