linux-kernel - Re: [alsa-devel] [PATCH v5 2/2] soundwire: qcom: add support for SoundWire controller

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Message-ID: <4dab7ee8-dc0e-bf61-24db-3e227c459575@linaro.org>
Date:   Fri, 10 Jan 2020 12:12:31 +0000
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        vkoul@...nel.org
Cc:     robh@...nel.org, bgoswami@...eaurora.org, broonie@...nel.org,
        lgirdwood@...il.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, spapothi@...eaurora.org
Subject: Re: [alsa-devel] [PATCH v5 2/2] soundwire: qcom: add support for
 SoundWire controller



On 19/12/2019 17:14, Srinivas Kandagatla wrote:
>>> +
>>> +    if (sts & SWRM_INTERRUPT_STATUS_CMD_ERROR) {
>>> +        ctrl->reg_read(ctrl, SWRM_CMD_FIFO_STATUS, &value);
>>> +        dev_err_ratelimited(ctrl->dev,
>>> +                    "CMD error, fifo status 0x%x\n",
>>> +                     value);
>>> +        ctrl->reg_write(ctrl, SWRM_CMD_FIFO_CMD, 0x1);
>>> +    }
>>> +
>>> +    if ((sts & SWRM_INTERRUPT_STATUS_NEW_SLAVE_ATTACHED) ||
>>> +        sts & SWRM_INTERRUPT_STATUS_CHANGE_ENUM_SLAVE_STATUS)
>>> +        schedule_work(&ctrl->slave_work);
>>> +
>>> +    ctrl->reg_write(ctrl, SWRM_INTERRUPT_CLEAR, sts);
>>
>> is it intentional to clear the interrupts first, before doing 
>> additional checks?
>>
> 
> No, I can move it to right to the end!

Reason why I did this was that if we run complete() before irq is 
cleared complete might trigger another read/write which can raise an 
interrupt. And with interrupt status not cleared we might miss it. This 
is very much timing dependent specially with the threaded irq.

So code needs no change atm!

> 
>> Or could it be done immediately after reading the status. It's not 
>> clear to me if the position of this clear matters, and if yes you 
>> should probably add a comment?
> 
> Am not 100% if it matters, but Ideally I would like clear the interrupt 
> source before clearing the interrupt.
> 
> 
>>
>>> +
>>> +    if (sts & SWRM_INTERRUPT_STATUS_SPECIAL_CMD_ID_FINISHED) {
>>> +        spin_lock_irqsave(&ctrl->comp_lock, flags);
>>> +        if (ctrl->comp)
>>> +            complete(ctrl->comp);
>>> +        spin_unlock_irqrestore(&ctrl->comp_lock, flags);
>>> +    }
>>> +
>>> +    return IRQ_HANDLED;
>> The rest looks fine. nice work. 

Thanks,
srini