Commits
Takashi Iwai committed 7169701ad3f
ALSA: hda - Workaround for unbalanced i915 power refcount by concurrent probe The recent addition of on-demand i915 audio component binding in the codec driver seems leading to the unbalanced i915 power refcount, according to Intel CI tests. Typically, it gets a kernel WARNING like: WARNING: CPU: 3 PID: 173 at sound/hda/hdac_i915.c:91 snd_hdac_display_power+0xf1/0x110 [snd_hda_core]() Call Trace: [<ffffffff813fef15>] dump_stack+0x67/0x92 [<ffffffff81078a21>] warn_slowpath_common+0x81/0xc0 [<ffffffff81078b15>] warn_slowpath_null+0x15/0x20 [<ffffffffa00f77e1>] snd_hdac_display_power+0xf1/0x110 [snd_hda_core] [<ffffffffa015039d>] azx_intel_link_power+0xd/0x10 [snd_hda_intel] [<ffffffffa011e32a>] azx_link_power+0x1a/0x30 [snd_hda_codec] [<ffffffffa00f21f9>] snd_hdac_link_power+0x29/0x40 [snd_hda_core] [<ffffffffa01192a6>] hda_codec_runtime_suspend+0x76/0xa0 [snd_hda_codec] ..... The scenario is like below: - HD-audio driver and i915 driver are probed concurrently at the (almost) same time; HDA bus tries to bind with i915, but it fails because i915 initialization is still being processed. - Later on, HD-audio probes the HDMI codec, where it again tries to bind with i915. At this time, it succeeds. - At finishing the probe of HDA, it decreases the refcount as if it were already bound at the bus probe, since the component is bound now. This triggers a kernel WARNING due to the unbalance. As a workaround, in this patch, we just disable the on-demand i915 component binding in the codec driver. This essentially reverts back to the state of 4.4 kernel. We know that this is no real solution, but it's a minimalistic simple change that can be applied to 4.5.x kernel as stable. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94566 Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Cc: <stable@vger.kernel.org> # v4.5 Signed-off-by: Takashi Iwai <tiwai@suse.de>