Hi Stephen,
On Fri, Oct 14, 2022 at 05:49:33PM -0700, Stephen Boyd wrote:
> This driver purely exposes information from memory to the kernel. Let's
> mark it as not having any device PM functionality, so that during
> suspend we skip even trying to call a suspend function on this device.
> This clears up suspend logs more than anything else, but it also shaves
> a few cycles off suspend.
>
> Cc: Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxx>
> Signed-off-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
> ---
>
> Resend to fix Bjorn's email.
>
> drivers/soc/qcom/cmd-db.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/soc/qcom/cmd-db.c b/drivers/soc/qcom/cmd-db.c
> index 629a7188b576..33856abd560c 100644
> --- a/drivers/soc/qcom/cmd-db.c
> +++ b/drivers/soc/qcom/cmd-db.c
> @@ -338,6 +338,8 @@ static int cmd_db_dev_probe(struct platform_device *pdev)
>
> debugfs_create_file("cmd-db", 0400, NULL, NULL, &cmd_db_debugfs_ops);
>
> + device_set_pm_not_required(&pdev->dev);
> +
> return 0;
> }
>
>
Sorry for asking this question here, thought it would be easy for you to
get the context.
I was recently reading this driver and learned about
device_set_pm_not_required() API. However, it is not clear how this is
working in practice?
The driver is calling device_set_pm_not_required() in probe(), however
all the checks for device_pm_not_required() happen before probe() is
called. For ex: dpm_sysfs_add() and device_pm_add() both happens before
probe(). I was expecting not to see
/sys/bus/platform/devices/XXXXXX.aop-cmd-db/power directory but it is
still present.
Also, I believe once driver set this flag, the device clean up might not
remove sysfs entries as we have device_pm_not_required() checks active
by that time.
Would it make sense to add code after probe() and take some action if
device_pm_not_required() returns true?
Thanks,
Pavan
