linux-kernel - Re: [PATCH 2/3] soc: qcom: Add AOSS QMP communication driver

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Message-ID: <20181226202830.GE9704@minitux>
Date:   Wed, 26 Dec 2018 12:28:30 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Arun Kumar Neelakantam <aneela@...eaurora.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] soc: qcom: Add AOSS QMP communication driver

On Tue 20 Nov 04:22 PST 2018, Arun Kumar Neelakantam wrote:

Thanks for the review Arun.

> On 11/12/2018 1:35 PM, Bjorn Andersson wrote:
[..]
> > +int qmp_send(struct qmp *qmp, const void *data, size_t len)
> > +{
> > +	int ret;
> > +
> > +	if (WARN_ON(len + sizeof(u32) > qmp->size)) {
> > +		dev_err(qmp->dev, "message too long\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	if (WARN_ON(len % sizeof(u32))) {
> > +		dev_err(qmp->dev, "message not 32-bit aligned\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	mutex_lock(&qmp->tx_lock);
> > +
> > +	if (!qmp_message_empty(qmp)) {
> > +		dev_err(qmp->dev, "mailbox left busy\n");
> > +		ret = -EINVAL;
> should it be -EBUSY ?

That makes more sense.

> And qmp_messge_empty will be done either by remote if it process the data
> else by this driver in TIMEOUT case, so does we need this check for every TX
> ? I think we can just reset to Zero once in open time.

Didn't think about that, should we really make the QMP link ready again
when we get a timeout? Can we expect that the firmware of the remote
side is ready to serve future messages?


Should we keep this check and remove the writel() below?

> > +		goto out_unlock;
> > +	}
> > +
> > +	/* The message RAM only implements 32-bit accesses */
> > +	__iowrite32_copy(qmp->msgram + qmp->offset + sizeof(u32),
> > +			 data, len / sizeof(u32));
> > +	writel(len, qmp->msgram + qmp->offset);
> > +	qmp_kick(qmp);
> > +
> > +	ret = wait_event_interruptible_timeout(qmp->event,
> > +					       qmp_message_empty(qmp), HZ);
> > +	if (!ret) {
> > +		dev_err(qmp->dev, "ucore did not ack channel\n");
> > +		ret = -ETIMEDOUT;
> > +
> > +		writel(0, qmp->msgram + qmp->offset);
> > +	} else {
> > +		ret = 0;
> > +	}
> > +
> > +out_unlock:
> > +	mutex_unlock(&qmp->tx_lock);
> > +
> > +	return ret;
> > +}

Regards,
Bjorn