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

[Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>]

On Mon, 14 Jul 2025 at 19:21, Praveen Talari <quic_ptalari@quicinc.com> wrote:
>
> Hi Dmitry/Bjorn/Krzysztof,
>
> Thank you for review.
>
> On 7/1/2025 4:42 PM, Dmitry Baryshkov wrote:
> > On Mon, Jun 30, 2025 at 10:40:25AM +0530, Praveen Talari wrote:
> >> 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?
> >>>
> >>> 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.
> >>
> >> Introduce PM runtime support to the Qualcomm GENI serial driver to enable
> >> better power efficiency and modularity across diverse resource control
> >> mechanisms, including Linux and firmware-managed systems.
> >>
> >> As part of this enhancement, the existing qcom_geni_serial_pm() logic to
> >> use standard PM runtime APIs such as pm_runtime_resume_and_get() and
> >> pm_runtime_put_sync(). Power state transitions are now handled through
> >> the geni_serial_resources_on() and geni_serial_resources_off() functions.
> >>
> >> Is it fine?
> >> Please guide me/correct me if needed
> >
> > Please start by stating out the problem that you are trying to solve.
> > There is no actual issue description in your patch.
>
> I hope this commit describes the actual problem.
>
> The GENI serial driver currently handles power resource management
> through calls to the statically defined geni_serial_resources_on() and
> geni_serial_resources_off() functions. This approach reduces modularity
> and limits support for platforms with diverse power management
> mechanisms, including resource managed by firmware.
>
> Improve modularity and enable better integration with platform-specific
> power management, introduce support for runtime PM. Use
> pm_runtime_resume_and_get() and pm_runtime_put_sync() within the
> qcom_geni_serial_pm() callback to control resource power state
> transitions based on UART power state changes.

LGTM

>
> Thanks,
> Praveen Talari
> >
> >>
> >> Thanks,
> >> Praveen Talari
> >>>
> >>> 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@linaro.org>
> >>>> Signed-off-by: Praveen Talari <quic_ptalari@quicinc.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
> >>>>
> >



-- 
With best wishes
Dmitry