On 4/17/2018 12:17 AM, Stephen Boyd wrote:
> Quoting Matthias Kaehlcke (2018-04-12 14:41:02)
>> On Mon, Apr 09, 2018 at 01:38:34PM -0600, Karthikeyan Ramasubramanian wrote:
>>> @@ -1103,6 +1107,14 @@ static int __maybe_unused qcom_geni_serial_sys_resume_noirq(struct device *dev)
>>>
>>> if (console_suspend_enabled && uport->suspended) {
>>> uart_resume_port(uport->private_data, uport);
>>> + /*
>>> + * uart_suspend_port() invokes port shutdown which in turn
>>> + * frees the irq. uart_resume_port invokes port startup which
>>> + * performs request_irq. The request_irq auto-enables the IRQ.
>>> + * In addition, resume_noirq implicitly enables the IRQ and
>>> + * leads to an unbalanced IRQ enable warning. Disable the IRQ
>>> + * before returning so that the warning is suppressed.
>>> + */
>>
>> For the record, the noirq flow is:
>>
>> dpm_resume_noirq()
>> dpm_noirq_resume_devices()
>> for each dev
>> device_resume_noirq()
>>
>> dpm_noirq_end()
>> resume_irqs()
>> for_each_irq_desc
>> resume_irq()
>>
>>
>
> I'm still curious why we use the noirq variants of the suspend/resume
> hooks. Why not use the normal suspend/resume hooks here and then drop
> the whole disable_irq() dance?
In the non-console use-cases, RX line can be used as a wake-up
interrupt. Using no_irq variant helps with turning on the serial engine
resources quickly and in turn help with reducing the RX latency.
>
>>> disable_irq(uport->irq);
>>> }
>>> return 0;
Regards,
Karthik.
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