ALSA: hda: Manage concurrent reg access more properly
In the commit 8e85def5 ("ALSA: hda: enable regmap internal locking"), we re-enabled the regmap lock due to the reported regression that showed the possible concurrent accesses. It was a temporary workaround, and there are still a few opened races even after the revert. In this patch, we cover those still opened windows with a proper mutex lock and disable the regmap internal lock again. First off, the patch introduces a new snd_hdac_device.regmap_lock mutex that is applied for each snd_hdac_regmap_*() call, including read, write and update helpers. The mutex is applied carefully so that it won't block the self-power-up procedure in the helper function. Also, this assures the protection for the accesses without regmap, too. The snd_hdac_regmap_update_raw() is refactored to use the standard regmap_update_bits_check() function instead of the open-code. The non-regmap case is still open-coded but it's an easy part. The all read and write operations are in the single mutex protection, so it's now race-free. In addition, a couple of new helper functions are added: snd_hdac_regmap_update_raw_once() and snd_hdac_regmap_sync(). Both are called from HD-audio legacy driver. The former is to initialize the given verb bits but only once when it's not initialized yet. Due to this condition, the function invokes regcache_cache_only(), and it's now performed inside the regmap_lock (formerly it was racy) too. The latter function is for simply invoking regcache_sync() inside the regmap_lock, which is called from the codec resume call path. Along with that, the HD-audio codec driver code is slightly modified / simplified to adapt those new functions. And finally, snd_hdac_regmap_read_raw(), *_write_raw(), etc are rewritten with the helper macro. It's just for simplification because the code logic is identical among all those functions. Tested-by: NKai Vehmanen <kai.vehmanen@linux.intel.com> Link: https://lore.kernel.org/r/20200109090104.26073-1-tiwai@suse.deSigned-off-by: NTakashi Iwai <tiwai@suse.de>
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