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

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Date:   Thu, 3 Jan 2019 23:18:39 +0530
From:   Arun Kumar Neelakantam <aneela@...eaurora.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.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 12/27/2018 1:58 AM, Bjorn Andersson wrote:
> 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?
I prefer we can just remove this check and keep writel() below same as 
down stream.
>
>>> +		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