linux-kernel - Re: [PATCH 1/7] soundwire: bus: use sdw_update_no

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Message-ID: <1db93c2e-3c87-bc5e-ddeb-56424870b897@linux.intel.com>
Date:   Sat, 5 Dec 2020 08:59:01 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Vinod Koul <vkoul@...nel.org>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>
Cc:     alsa-devel@...a-project.org, tiwai@...e.de,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        ranjani.sridharan@...ux.intel.com, hui.wang@...onical.com,
        broonie@...nel.org, srinivas.kandagatla@...aro.org,
        jank@...ence.com, sanyog.r.kale@...el.com,
        rander.wang@...ux.intel.com, bard.liao@...el.com
Subject: Re: [PATCH 1/7] soundwire: bus: use sdw_update_no_pm when
 initializing a device

Thanks for the review Vinod.

On 12/5/20 1:45 AM, Vinod Koul wrote:
> On 03-12-20, 04:46, Bard Liao wrote:
>> From: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
>>
>> When a Slave device is resumed, it may resume the bus and restart the
>> enumeration. During that process, we absolutely don't want to call
>> regular read/write routines which will wait for the resume to
>> complete, otherwise a deadlock occurs.
>>
>> Fixes: 60ee9be25571 ('soundwire: bus: add PM/no-PM versions of read/write functions')
> 
> Change looks okay, but not sure why this is a fix for adding no pm
> version?

when we added the no_pm version, we missed the two cases below where 
sdw_update() was used and that creates a deadlock. To me that's a 
conceptual bug, we didn't fully use the no_pm versions, hence the Fixes tag.

It's ok to remove the tag if you don't think it's useful/relevant, what 
matters is that we agree on the content.

>> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
>> Reviewed-by: Rander Wang <rander.wang@...ux.intel.com>
>> Signed-off-by: Bard Liao <yung-chuan.liao@...ux.intel.com>
>> ---
>>   drivers/soundwire/bus.c | 16 ++++++++++++++--
>>   1 file changed, 14 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
>> index d1e8c3a54976..60c42508c6c6 100644
>> --- a/drivers/soundwire/bus.c
>> +++ b/drivers/soundwire/bus.c
>> @@ -489,6 +489,18 @@ sdw_read_no_pm(struct sdw_slave *slave, u32 addr)
>>   		return buf;
>>   }
>>   
>> +static int sdw_update_no_pm(struct sdw_slave *slave, u32 addr, u8 mask, u8 val)
>> +{
>> +	int tmp;
>> +
>> +	tmp = sdw_read_no_pm(slave, addr);
>> +	if (tmp < 0)
>> +		return tmp;
>> +
>> +	tmp = (tmp & ~mask) | val;
>> +	return sdw_write_no_pm(slave, addr, tmp);
>> +}
>> +
>>   /**
>>    * sdw_nread() - Read "n" contiguous SDW Slave registers
>>    * @slave: SDW Slave
>> @@ -1256,7 +1268,7 @@ static int sdw_initialize_slave(struct sdw_slave *slave)
>>   	val = slave->prop.scp_int1_mask;
>>   
>>   	/* Enable SCP interrupts */
>> -	ret = sdw_update(slave, SDW_SCP_INTMASK1, val, val);
>> +	ret = sdw_update_no_pm(slave, SDW_SCP_INTMASK1, val, val);
>>   	if (ret < 0) {
>>   		dev_err(slave->bus->dev,
>>   			"SDW_SCP_INTMASK1 write failed:%d\n", ret);
>> @@ -1271,7 +1283,7 @@ static int sdw_initialize_slave(struct sdw_slave *slave)
>>   	val = prop->dp0_prop->imp_def_interrupts;
>>   	val |= SDW_DP0_INT_PORT_READY | SDW_DP0_INT_BRA_FAILURE;
>>   
>> -	ret = sdw_update(slave, SDW_DP0_INTMASK, val, val);
>> +	ret = sdw_update_no_pm(slave, SDW_DP0_INTMASK, val, val);
>>   	if (ret < 0)
>>   		dev_err(slave->bus->dev,
>>   			"SDW_DP0_INTMASK read failed:%d\n", ret);
>> -- 
>> 2.17.1
>