linux-kernel - Re: [PATCH v6 7/8] serial: qcom-geni: Enable PM runtime for serial driver

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Message-ID: <d6cr4elhrbh27lmlcv5xzuel75uvsgi7klxjkevm7vg4jcbawe@5ojgetrxkag5>
Date: Tue, 17 Jun 2025 10:53:54 -0500
From: Bjorn Andersson <andersson@...nel.org>
To: Praveen Talari <quic_ptalari@...cinc.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Jiri Slaby <jirislaby@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Konrad Dybcio <konradybcio@...nel.org>, linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-serial@...r.kernel.org, devicetree@...r.kernel.org, psodagud@...cinc.com, 
	djaggi@...cinc.com, quic_msavaliy@...cinc.com, quic_vtanuku@...cinc.com, 
	quic_arandive@...cinc.com, quic_mnaresh@...cinc.com, quic_shazhuss@...cinc.com
Subject: Re: [PATCH v6 7/8] serial: qcom-geni: Enable PM runtime for serial
 driver

On Fri, Jun 06, 2025 at 10:51:13PM +0530, Praveen Talari wrote:
> Add Power Management (PM) runtime support to Qualcomm GENI
> serial driver.
> 

Doesn't this have impact on the behavior outside of your
project? Or is the transition from qcom_geni_serial_pm() to explicit
RPM merely moving code around?

Seems like this deserves to not be hidden in a middle of a patch series.

> Introduce necessary callbacks and updates to ensure seamless
> transitions between power states, enhancing overall power
> efficiency.
> 

This commit message fails to state why we need runtime PM support in the
driver.

Also, start your commit message with a problem description, per
https://docs.kernel.org/process/submitting-patches.html#describe-your-changes

> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
> Signed-off-by: Praveen Talari <quic_ptalari@...cinc.com>
> ---
> v5 -> v6
> - added reviewed-by tag in commit
> - added __maybe_unused to PM callback functions to avoid
>   warnings of defined but not used
> ---
>  drivers/tty/serial/qcom_geni_serial.c | 33 +++++++++++++++++++++++----
>  1 file changed, 29 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
> index b6fa7dc9b1fb..3691340ce7e8 100644
> --- a/drivers/tty/serial/qcom_geni_serial.c
> +++ b/drivers/tty/serial/qcom_geni_serial.c
> @@ -1686,10 +1686,10 @@ static void qcom_geni_serial_pm(struct uart_port *uport,
>  		old_state = UART_PM_STATE_OFF;
>  
>  	if (new_state == UART_PM_STATE_ON && old_state == UART_PM_STATE_OFF)
> -		geni_serial_resources_on(uport);
> +		pm_runtime_resume_and_get(uport->dev);
>  	else if (new_state == UART_PM_STATE_OFF &&
>  		 old_state == UART_PM_STATE_ON)
> -		geni_serial_resources_off(uport);
> +		pm_runtime_put_sync(uport->dev);
>  
>  }
>  
> @@ -1827,9 +1827,11 @@ static int qcom_geni_serial_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> +	pm_runtime_enable(port->se.dev);

Any reason not to use devm_pm_runtime_enable() and avoid the
two pm_runtime_disable() below?

Regards,
Bjorn

> +
>  	ret = uart_add_one_port(drv, uport);
>  	if (ret)
> -		return ret;
> +		goto error;
>  
>  	if (port->wakeup_irq > 0) {
>  		device_init_wakeup(&pdev->dev, true);
> @@ -1839,11 +1841,15 @@ static int qcom_geni_serial_probe(struct platform_device *pdev)
>  			device_init_wakeup(&pdev->dev, false);
>  			ida_free(&port_ida, uport->line);
>  			uart_remove_one_port(drv, uport);
> -			return ret;
> +			goto error;
>  		}
>  	}
>  
>  	return 0;
> +
> +error:
> +	pm_runtime_disable(port->se.dev);
> +	return ret;
>  }
>  
>  static void qcom_geni_serial_remove(struct platform_device *pdev)
> @@ -1855,9 +1861,26 @@ static void qcom_geni_serial_remove(struct platform_device *pdev)
>  	dev_pm_clear_wake_irq(&pdev->dev);
>  	device_init_wakeup(&pdev->dev, false);
>  	ida_free(&port_ida, uport->line);
> +	pm_runtime_disable(port->se.dev);
>  	uart_remove_one_port(drv, &port->uport);
>  }
>  
> +static int __maybe_unused qcom_geni_serial_runtime_suspend(struct device *dev)
> +{
> +	struct qcom_geni_serial_port *port = dev_get_drvdata(dev);
> +	struct uart_port *uport = &port->uport;
> +
> +	return geni_serial_resources_off(uport);
> +}
> +
> +static int __maybe_unused qcom_geni_serial_runtime_resume(struct device *dev)
> +{
> +	struct qcom_geni_serial_port *port = dev_get_drvdata(dev);
> +	struct uart_port *uport = &port->uport;
> +
> +	return geni_serial_resources_on(uport);
> +}
> +
>  static int qcom_geni_serial_suspend(struct device *dev)
>  {
>  	struct qcom_geni_serial_port *port = dev_get_drvdata(dev);
> @@ -1901,6 +1924,8 @@ static const struct qcom_geni_device_data qcom_geni_uart_data = {
>  };
>  
>  static const struct dev_pm_ops qcom_geni_serial_pm_ops = {
> +	SET_RUNTIME_PM_OPS(qcom_geni_serial_runtime_suspend,
> +			   qcom_geni_serial_runtime_resume, NULL)
>  	SYSTEM_SLEEP_PM_OPS(qcom_geni_serial_suspend, qcom_geni_serial_resume)
>  };
>  
> -- 
> 2.17.1
>