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

[Praveen Talari]

Hi Bjorn,

Thank you for review.

On 6/17/2025 9:23 PM, Bjorn Andersson wrote:
> 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?
There is no impact on functionality and behavior with this change.

The transition is purely refactor.

Using PM runtime APIs such as
pm_runtime_resume_and_get() and pm_runtime_put_sync() to manage resource 
both locally and firmware.

> Seems like this deserves to not be hidden in a middle of a patch series.
This depends on refactored patches.
> > 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.
Sure, will update commit text.
> 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@xxxxxxxxxx>
> > Signed-off-by: Praveen Talari <quic_ptalari@xxxxxxxxxxx>
> > ---
> > 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?

I agree, will update in next patch-set.
> 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