linux-kernel - Re: [PATCH 3/7] soundwire: intel: add mutex to prevent concurrent access to SHIM registers

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Message-ID: <a989368c-5a57-a726-0816-2e389d733ae0@linux.intel.com>
Date:   Fri, 20 Mar 2020 09:07:45 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        tiwai@...e.de, broonie@...nel.org, gregkh@...uxfoundation.org,
        jank@...ence.com, srinivas.kandagatla@...aro.org,
        slawomir.blauciak@...el.com,
        Bard liao <yung-chuan.liao@...ux.intel.com>,
        Rander Wang <rander.wang@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Hui Wang <hui.wang@...onical.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>
Subject: Re: [PATCH 3/7] soundwire: intel: add mutex to prevent concurrent
 access to SHIM registers


>> diff --git a/drivers/soundwire/intel.h b/drivers/soundwire/intel.h
>> index 38b7c125fb10..568c84a80d79 100644
>> --- a/drivers/soundwire/intel.h
>> +++ b/drivers/soundwire/intel.h
>> @@ -15,6 +15,7 @@
>>    * @irq: Interrupt line
>>    * @ops: Shim callback ops
>>    * @dev: device implementing hw_params and free callbacks
>> + * @shim_lock: mutex to handle access to shared SHIM registers
>>    */
>>   struct sdw_intel_link_res {
>>   	struct platform_device *pdev;
>> @@ -25,6 +26,7 @@ struct sdw_intel_link_res {
>>   	int irq;
>>   	const struct sdw_intel_ops *ops;
>>   	struct device *dev;
>> +	struct mutex *shim_lock; /* protect shared registers */
> 
> Where is this mutex initialized? Did you test this...

Dude, we've been testing the heck out of SoundWire.

If you want to see the actual initialization it's in the intel_init.c code:

https://github.com/thesofproject/linux/blob/9c7487b33072040ab755d32ca173b75151c0160c/drivers/soundwire/intel_init.c#L231

And this was clearly stated in the cover letter:

"Reviewers might object that the code is provided without some required
initializations for mutexes and shim masks, they will be added as part
of the transition to sdw_master_device - still stuck as of 3/11."