linux-kernel - Re: [PATCH v3 3/3] soundwire: qcom: add in-band wake up interrupt support

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Date:   Mon, 28 Feb 2022 12:01:21 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        robh+dt@...nel.org, vkoul@...nel.org,
        yung-chuan.liao@...ux.intel.com
Cc:     devicetree@...r.kernel.org, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, quic_srivasam@...cinc.com
Subject: Re: [PATCH v3 3/3] soundwire: qcom: add in-band wake up interrupt
 support


> @@ -1424,6 +1464,11 @@ static int swrm_runtime_resume(struct device *dev)
>  	struct qcom_swrm_ctrl *ctrl = dev_get_drvdata(dev);
>  	int ret;
>  
> +	if (ctrl->wake_irq > 0) {
> +		if (!irqd_irq_disabled(irq_get_irq_data(ctrl->wake_irq)))
> +			disable_irq_nosync(ctrl->wake_irq);
> +	}
> +
>  	clk_prepare_enable(ctrl->hclk);

This one is quite interesting. If you disable the IRQ mechanism but
haven't yet resumed the clock, that leaves a time window where the
peripheral could attempt to drive the line high. what happens in that case?

>  
>  	if (ctrl->clock_stop_not_supported) {
> @@ -1491,6 +1536,11 @@ static int __maybe_unused swrm_runtime_suspend(struct device *dev)
>  
>  	usleep_range(300, 305);
>  
> +	if (ctrl->wake_irq > 0) {
> +		if (irqd_irq_disabled(irq_get_irq_data(ctrl->wake_irq)))
> +			enable_irq(ctrl->wake_irq);
> +	}
> +

and this one is similar, you could have a case where the peripheral
signals a wake immediately after the ClockStopNow frame, but you may not
yet have enabled the wake detection interrupt.

Would that imply that the wake is missed?



>  	return 0;
>  }
>