linux-kernel - Re: [RESEND PATCH v2 07/15] ASoC: qcom: q6asm: Add support to memory map and unmap

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Message-ID: <20180103193916.GZ478@tuxbook>
Date:   Wed, 3 Jan 2018 11:39:16 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        Mark Brown <broonie@...nel.org>, linux-arm-msm@...r.kernel.org,
        alsa-devel@...a-project.org, Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org,
        Banajit Goswami <bgoswami@...eaurora.org>,
        linux-kernel@...r.kernel.org, Patrick Lai <plai@...eaurora.org>,
        Takashi Iwai <tiwai@...e.com>, sboyd@...eaurora.org,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        David Brown <david.brown@...aro.org>,
        Rob Herring <robh+dt@...nel.org>, linux-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RESEND PATCH v2 07/15] ASoC: qcom: q6asm: Add support to memory
 map and unmap

On Wed 03 Jan 08:26 PST 2018, Srinivas Kandagatla wrote:

> Thanks for your review comments.
> 
> On 02/01/18 05:48, Bjorn Andersson wrote:
> > On Thu 14 Dec 09:33 PST 2017, srinivas.kandagatla@...aro.org wrote:
[..]
> > > +int q6asm_unmap_memory_regions(unsigned int dir, struct audio_client *ac)
> > > +{
> > > +	struct audio_port_data *port;
> > > +	int cnt = 0;
> > > +	int rc = 0;
> > > +
> > > +	mutex_lock(&ac->cmd_lock);
> > > +	port = &ac->port[dir];
> > > +	if (!port->buf) {
> > > +		mutex_unlock(&ac->cmd_lock);
> > > +		return 0;
> > 
> > Put a label right before the mutex_unlock below and return rc instead of
> > 0, then you can replace these two lines with "goto unlock"
> > 
> > > +	}
> > > +	cnt = port->max_buf_cnt - 1;
> > 
> > What if we mapped 1 period? Why shouldn't we enter the unmap path?
> > 
> It would enter into unmap path, as cnt  would be 0 for 1 period.
> 

You're right, I missed the = in the comparison, but I don't see a reason
to subtract 1. It seems like the max_buf_cnt might have been used
differently in the past?

I suggest that you drop the - 1 and change the comparison to cnt > 0, if
nothing else to not confuse me if I read this code again ;)

> > > +	if (cnt >= 0) {
[..]
> > > +int q6asm_map_memory_regions(unsigned int dir, struct audio_client *ac,
> > > +			     dma_addr_t phys,
> > > +			     unsigned int period_sz, unsigned int periods)
[..]
> > > +		ac->port[dir].max_buf_cnt = 0;
> > > +		kfree(buf);
> > > +		ac->port[dir].buf = NULL;
> > 
> > These operations are done without holding cmd_lock.
> > 
> I will revisit such instances where the buf is not protected.
> 

NB. I got the impression that cmd_lock was actually the port_lock in
most places.

Regards,
Bjorn