Re: [v2, 1/8] tty: serial: qcom_geni_serial: Add comments for clarification

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On Mon, Apr 09, 2018 at 01:38:34PM -0600, Karthikeyan Ramasubramanian wrote:
> * Document reason for newline character counting in console_write
> * Document reason for disabling IRQ in the system resume operation
> 
> Signed-off-by: Karthikeyan Ramasubramanian <kramasub@xxxxxxxxxxxxxx>
> ---
>  drivers/tty/serial/qcom_geni_serial.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
> index a1b3eb0..1652b1f 100644
> --- a/drivers/tty/serial/qcom_geni_serial.c
> +++ b/drivers/tty/serial/qcom_geni_serial.c
> @@ -286,6 +286,10 @@ static void qcom_geni_serial_wr_char(struct uart_port *uport, int ch)
>  	u32 bytes_to_send = count;
>  
>  	for (i = 0; i < count; i++) {
> +		/*
> +		 * uart_console_write() adds a carriage return for each newline.
> +		 * Account for additional bytes to be written.
> +		 */
>  		if (s[i] == '\n')
>  			bytes_to_send++;
>  	}
> @@ -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()


>  		disable_irq(uport->irq);
>  	}
>  	return 0;

Reviewed-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
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