Re: [PATCH v7 7/8] serial: qcom-geni: Enable PM runtime for serial driver

[Praveen Talari <quic_ptalari@quicinc.com>]

Hi Alexey.

Thank you for your patience,

On 8/12/2025 3:35 PM, Alexey Klimov wrote:
> (c/c Neil and Srini)
> 
> On Mon Jul 21, 2025 at 6:45 PM BST, Praveen Talari wrote:
>> 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.
>>
>> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
>> Signed-off-by: Praveen Talari <quic_ptalari@quicinc.com>
> 
> 
> This breaks at least RB1 (QRB2210), maybe others.
> Currently broken on -master and on linux-next.
> 
> Upon login prompt random parts of kernel seems to be off/failed and
> debugging led to udev being stuck:
> 
> [   85.369834] INFO: task kworker/u16:0:12 blocked for more than 42 seconds.
> [   85.376699]       Not tainted 6.17.0-rc1-00004-g53e760d89498 #9
> [   85.382660] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [   85.390547] task:kworker/u16:0   state:D stack:0     pid:12    tgid:12    ppid:2      task_flags:0x4208060 flags:0x00000010
> [   85.401748] Workqueue: async async_run_entry_fn
> [   85.406349] Call trace:
> [   85.408828]  __switch_to+0xe8/0x1a0 (T)
> [   85.412724]  __schedule+0x290/0x7c0
> [   85.416275]  schedule+0x34/0x118
> [   85.419554]  rpm_resume+0x14c/0x66c
> [   85.423111]  rpm_resume+0x2a4/0x66c
> [   85.426647]  rpm_resume+0x2a4/0x66c
> [   85.430188]  rpm_resume+0x2a4/0x66c
> [   85.433722]  __pm_runtime_resume+0x50/0x9c
> [   85.437869]  __driver_probe_device+0x58/0x120
> [   85.442287]  driver_probe_device+0x3c/0x154
> [   85.446523]  __driver_attach_async_helper+0x4c/0xc0
> [   85.451446]  async_run_entry_fn+0x34/0xe0
> [   85.455504]  process_one_work+0x148/0x290
> [   85.459565]  worker_thread+0x2c4/0x3e0
> [   85.463368]  kthread+0x118/0x1c0
> [   85.466651]  ret_from_fork+0x10/0x20
> [   85.470337] INFO: task irq/92-4a8c000.:71 blocked for more than 42 seconds.
> [   85.477351]       Not tainted 6.17.0-rc1-00004-g53e760d89498 #9
> [   85.483323] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [   85.491195] task:irq/92-4a8c000. state:D stack:0     pid:71    tgid:71    ppid:2      task_flags:0x208040 flags:0x00000010
> [   85.502290] Call trace:
> [   85.504786]  __switch_to+0xe8/0x1a0 (T)
> [   85.508687]  __schedule+0x290/0x7c0
> [   85.512231]  schedule+0x34/0x118
> [   85.515504]  __synchronize_irq+0x60/0xa0
> [   85.519483]  disable_irq+0x3c/0x4c
> [   85.522929]  msm_pinmux_set_mux+0x3a8/0x44c
> [   85.527167]  pinmux_enable_setting+0x1c4/0x28c
> [   85.531665]  pinctrl_commit_state+0xa0/0x260
> [   85.535989]  pinctrl_pm_select_default_state+0x4c/0xa0
> [   85.541182]  geni_se_resources_on+0xd0/0x15c
> [   85.545522]  geni_serial_resource_state+0x8c/0xbc
> [   85.550282]  qcom_geni_serial_runtime_resume+0x24/0x3c
> [   85.555470]  pm_generic_runtime_resume+0x2c/0x44
> [   85.560139]  __rpm_callback+0x48/0x1e0
> [   85.563949]  rpm_callback+0x74/0x80
> [   85.567494]  rpm_resume+0x39c/0x66c
> [   85.571040]  __pm_runtime_resume+0x50/0x9c
> [   85.575193]  handle_threaded_wake_irq+0x30/0x80
> [   85.579771]  irq_thread_fn+0x2c/0xb0
> [   85.583443]  irq_thread+0x16c/0x278
> [   85.587003]  kthread+0x118/0x1c0
> [   85.590283]  ret_from_fork+0x10/0x20
> [   85.593943] INFO: task (udev-worker):228 blocked for more than 42 seconds.
> [   85.600873]       Not tainted 6.17.0-rc1-00004-g53e760d89498 #9
> [   85.606846] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [   85.614717] task:(udev-worker)   state:D stack:0     pid:228   tgid:228   ppid:222    task_flags:0x400140 flags:0x00000818
> [   85.625823] Call trace:
> [   85.628316]  __switch_to+0xe8/0x1a0 (T)
> [   85.632217]  __schedule+0x290/0x7c0
> [   85.635765]  schedule+0x34/0x118
> [   85.639044]  async_synchronize_cookie_domain.part.0+0x50/0xa4
> [   85.644854]  async_synchronize_full+0x78/0xa0
> [   85.649270]  do_init_module+0x190/0x23c
> [   85.653154]  load_module+0x1708/0x1ca0
> [   85.656952]  init_module_from_file+0x74/0xa0
> [   85.661273]  __arm64_sys_finit_module+0x130/0x2f8
> [   85.666023]  invoke_syscall+0x48/0x104
> [   85.669842]  el0_svc_common.constprop.0+0xc0/0xe0
> [   85.674604]  do_el0_svc+0x1c/0x28
> [   85.677973]  el0_svc+0x2c/0x84
> [   85.681078]  el0t_64_sync_handler+0xa0/0xe4
> [   85.685316]  el0t_64_sync+0x198/0x19c
> [   85.689032] INFO: task (udev-worker):229 blocked for more than 42 seconds.
> 
> 
> Usually wifi, all remoteprocs and anything that depends on lpass/pinctrl fail to probe.

May i know what is testcase which you are running on target?
what is target?
Which usecase is this issue occurring in?

Thanks,
Praveen Talari
> 
> Reverting these:
> 86fa39dd6fb7 serial: qcom-geni: Enable Serial on SA8255p Qualcomm platforms
> 1afa70632c39 serial: qcom-geni: Enable PM runtime for serial driver
> 
> resolves the regression. Couldn't say if we should go with reverting since 86fa39dd6fb7
> adds support of serial on SA8255p and for clean revert both have to be reverted.
> 
> Any thoughts?
> 
> Best regards,
> Alexey
> 
> 
> 
> 
> 
>> ---
>> v6 -> v7
>>  From Bjorn:
>> - used devm_pm_runtime_enable() instead of pm_runtime_enable()
>> - updated commit text.
>>
>> 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 | 24 ++++++++++++++++++++++--
>>   1 file changed, 22 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
>> index 81f385d900d0..aa08de659e34 100644
>> --- a/drivers/tty/serial/qcom_geni_serial.c
>> +++ b/drivers/tty/serial/qcom_geni_serial.c
>> @@ -1713,10 +1713,10 @@ 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);
>>   
>>   }
>>   
>> @@ -1878,6 +1878,8 @@ static int qcom_geni_serial_probe(struct platform_device *pdev)
>>   	if (ret)
>>   		return ret;
>>   
>> +	devm_pm_runtime_enable(port->se.dev);
>> +
>>   	ret = uart_add_one_port(drv, uport);
>>   	if (ret)
>>   		return ret;
>> @@ -1909,6 +1911,22 @@ static void qcom_geni_serial_remove(struct platform_device *pdev)
>>   	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);
>> @@ -1952,6 +1970,8 @@ 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)
>>   };
>>   
>