Re: [PATCH 1/7] soundwire: bus: use sdw_update_no_pm when initializing a device

[Pierre-Louis Bossart]

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@xxxxxxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxxxxxx>
> > Reviewed-by: Rander Wang <rander.wang@xxxxxxxxxxxxxxx>
> > Signed-off-by: Bard Liao <yung-chuan.liao@xxxxxxxxxxxxxxx>
> > ---
> >   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