linux-kernel - [RFC PATCH 2/2] ASoC: SOF: trigger re-probing of deferred devices from workqueue

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Date:   Tue, 17 Aug 2021 14:00:57 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     alsa-devel@...a-project.org
Cc:     tiwai@...e.de, broonie@...nel.org, vkoul@...nel.org,
        liam.r.girdwood@...ux.intel.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@....de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Daniel Baluta <daniel.baluta@....com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        sound-open-firmware@...a-project.org (moderated list:SOUND - SOUND OPEN
        FIRMWARE (SOF) DRIVERS)
Subject: [RFC PATCH 2/2] ASoC: SOF: trigger re-probing of deferred devices from workqueue

Audio drivers such as HDaudio legacy and SOF rely on a workqueue to
split the probe into two, with a first pass returning success
immediately, and the second pass taking a lot more time due to the use
of request_module() and the DSP initializations.

This workqueue-based solution helps deal with conflicting requirements
a) other drivers should not be blocked by a long probe
b) a PROBE_PREFER_ASYNCHRONOUS probe_type is explicitly not allowed
to avoid a deadlock when request_module() is used.

This patch makes sure the deferred probe framework is triggered when
the provider of resources successfully completes its initialization.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
---
 sound/soc/sof/core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sound/soc/sof/core.c b/sound/soc/sof/core.c
index 3e4dd4a86363..cecc0e914807 100644
--- a/sound/soc/sof/core.c
+++ b/sound/soc/sof/core.c
@@ -251,6 +251,9 @@ static int sof_probe_continue(struct snd_sof_dev *sdev)
 
 	sdev->probe_completed = true;
 
+	/* kick-off re-probing of deferred devices */
+	driver_deferred_probe_trigger();
+
 	return 0;
 
 fw_trace_err:
-- 
2.25.1