linux-kernel - Re: [alsa-devel] [PATCH 04/14] soundwire: Add MIPI DisCo property helpers

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Date:   Fri, 20 Oct 2017 10:55:18 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        ALSA <alsa-devel@...a-project.org>,
        Charles Keepax <ckeepax@...nsource.cirrus.com>,
        Sudheer Papothi <spapothi@...eaurora.org>, plai@...eaurora.org,
        LKML <linux-kernel@...r.kernel.org>,
        Pierre <pierre-louis.bossart@...ux.intel.com>,
        patches.audio@...el.com, Mark <broonie@...nel.org>,
        srinivas.kandagatla@...aro.org, Shreyas NC <shreyas.nc@...el.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        Sagar Dharia <sdharia@...eaurora.org>, alan@...ux.intel.com
Subject: Re: [alsa-devel] [PATCH 04/14] soundwire: Add MIPI DisCo property
 helpers

On Thu, Oct 19, 2017 at 11:02:02AM +0200, Takashi Iwai wrote:
> On Thu, 19 Oct 2017 05:03:20 +0200,
> Vinod Koul wrote:
> >  
> > +	slave->ops = drv->ops;
> > +
> >  	ret = drv->probe(slave, id);
> >  	if (ret) {
> >  		dev_err(dev, "Probe of %s failed: %d\n", drv->name, ret);
> >  		return ret;
> >  	}
> >  
> > +	/* device is probed so let's read the properties now */
> > +	if (slave->ops && slave->ops->read_prop)
> > +		slave->ops->read_prop(slave);
> > +
> > +	/*
> > +	 * Check for valid clk_stop_timeout, use DisCo worst case value of
> > +	 * 300ms
> > +	 */
> > +	if (slave->prop.clk_stop_timeout == 0)
> > +		slave->prop.clk_stop_timeout = 300;
> > +
> > +	slave->bus->clk_stop_timeout = max_t(u32, slave->bus->clk_stop_timeout,
> > +					slave->prop.clk_stop_timeout);
> 
> Isn't it racy?
> Also what happens after removing a driver?  The clk_stop_timeout is
> kept high?

Well the spec mandates 300 as worst case, in practice this _should_ be
lesser. I need to double check on behaviour of clock stop on driver removal.
We need to keep in mind that multiple Slaves can be on a bus and removal
maybe from one of them, so we may not do clock stop.

> > +
> > +int sdw_slave_read_dpn(struct sdw_slave *slave,
> > +		struct sdw_dpn_prop *dpn, int count, int ports, char *type)
> 
> Missing comment for a public API function.

Ah missed this one. It was made public for debug, lets make it static now :)

-- 
~Vinod