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Date: Wed, 8 May 2019 23:11:57 -0700
From: Furquan Shaikh <furquan@...gle.com>
To: "Rafael J . Wysocki" <rjw@...ysocki.net>,
Len Brown <lenb@...nel.org>
Cc: ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Rajat Jain <rajatja@...gle.com>,
Duncan Laurie <dlaurie@...gle.com>,
Todd Broch <tbroch@...gle.com>
Subject: Re: [PATCH] drivers/acpi: Turn off power resources while entering S5
On Tue, Apr 23, 2019 at 4:39 PM Furquan Shaikh <furquan@...gle.com> wrote:
>
> During boot-up, ACPI bus scan enables all power resources so that
> respective device drivers can talk to their device. This causes acpi
> ref_count for the power resource to be incremented to 1. When system
> suspends (S3/S0ix) or hibernates(S4), DPM is responsible for calling
> power off on all power resources whose ref_count is 1 i.e. no other
> user of this power resource and thus resulting in _OFF routine being
> called for it.
>
> However, in case of poweroff, DPM is not involved and so the power
> resources are left on when the system is entering S5. This results in
> the violation of power down sequencing for certain devices
> e.g. touchscreen or digitizer I2C devices. In order to ensure that the
> power down sequencing does the right thing, it is necessary for ACPI
> to disable all power resources while preparing for S5.
>
> This change updates the function acpi_turn_off_unused_power_resources
> to accept a parameter acpi_system_state, This function turns off power
> resources according to the targeted system ACPI state:
> 1. For S0: Unused power resources are turned off i.e. power resources
> whose ref_count is already 0.
> 2. For S5: ref_count is decremented first to undo the increment
> performed during ACPI bus scan and then power resources with ref_count
> 0 are turned off.
> 3. All other suspend/hibernate states: No action is required since DPM
> takes care of turning off power resources.
>
> This change should not affect the wake capable devices since:
> 1. If wake capable devices are enabled before this call, their
> refcount should be greater than 1. Thus, they won't be turned off.
> 2. If wake capable devices are not enabled yet when this call is made,
> they would eventually get turned on by call to
> acpi_enable_wakeup_devices.
>
> Signed-off-by: Furquan Shaikh <furquan@...gle.com>
> ---
> drivers/acpi/power.c | 47 ++++++++++++++++++++++++++++++++++++++------
> drivers/acpi/sleep.c | 5 ++++-
> drivers/acpi/sleep.h | 2 +-
> 3 files changed, 46 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/acpi/power.c b/drivers/acpi/power.c
> index 665e93ca0b40f..945db762861a3 100644
> --- a/drivers/acpi/power.c
> +++ b/drivers/acpi/power.c
> @@ -889,10 +889,42 @@ void acpi_resume_power_resources(void)
>
> mutex_unlock(&power_resource_list_lock);
> }
> +#endif
>
> -void acpi_turn_off_unused_power_resources(void)
> +/**
> + * acpi_turn_off_power_resources: This function is used to turn off power
> + * resources in provided ACPI system state.
> + *
> + * Behavior differs based on the target system state:
> + * ACPI_STATE_S0: Turn off unused power resources i.e. turn off power resources
> + * with ref_count zero.
> + * ACPI_STATE_S5: Decrement ref_count first and turn off power resources with
> + * ref_count zero. This is done to ensure that the ref_count
> + * incremented during ACPI bus scan is undone and any power
> + * resources that are not required during S5 are turned off.
> + * ACPI_STATE_Sx: No action required. DPM is responsible for turning off power
> + * resources while suspending/hibernating.
> + */
> +void acpi_turn_off_power_resources(int acpi_system_state)
> {
> struct acpi_power_resource *resource;
> + int decrement;
> +
> + if (acpi_system_state == ACPI_STATE_S0) {
> + /*
> + * In case of ACPI_STATE_S0, turn off only unused power
> + * resources. So, no need to decrement ref_count.
> + */
> + decrement = 0;
> + } else if (acpi_system_state == ACPI_STATE_S5) {
> + /*
> + * In case of ACPI_STATE_S5, ref_count needs to be decremented
> + * first before checking if it is okay to power off the
> + * resource.
> + */
> + decrement = 1;
> + } else
> + return;
>
> mutex_lock(&power_resource_list_lock);
>
> @@ -907,10 +939,14 @@ void acpi_turn_off_unused_power_resources(void)
> continue;
> }
>
> - if (state == ACPI_POWER_RESOURCE_STATE_ON
> - && !resource->ref_count) {
> - dev_info(&resource->device.dev, "Turning OFF\n");
> - __acpi_power_off(resource);
> + if (state == ACPI_POWER_RESOURCE_STATE_ON) {
> + if (resource->ref_count)
> + resource->ref_count -= decrement;
> +
> + if (!resource->ref_count) {
> + dev_info(&resource->device.dev, "Turning OFF\n");
> + __acpi_power_off(resource);
> + }
> }
>
> mutex_unlock(&resource->resource_lock);
> @@ -918,4 +954,3 @@ void acpi_turn_off_unused_power_resources(void)
>
> mutex_unlock(&power_resource_list_lock);
> }
> -#endif
> diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
> index 403c4ff153498..fb6b3ca0eeb91 100644
> --- a/drivers/acpi/sleep.c
> +++ b/drivers/acpi/sleep.c
> @@ -75,6 +75,9 @@ static int acpi_sleep_prepare(u32 acpi_state)
> printk(KERN_INFO PREFIX "Preparing to enter system sleep state S%d\n",
> acpi_state);
> acpi_enable_wakeup_devices(acpi_state);
> +
> + acpi_turn_off_power_resources(acpi_state);
> +
> acpi_enter_sleep_state_prep(acpi_state);
> return 0;
> }
> @@ -524,7 +527,7 @@ static void acpi_pm_start(u32 acpi_state)
> */
> static void acpi_pm_end(void)
> {
> - acpi_turn_off_unused_power_resources();
> + acpi_turn_off_power_resources(ACPI_STATE_S0);
> acpi_scan_lock_release();
> /*
> * This is necessary in case acpi_pm_finish() is not called during a
> diff --git a/drivers/acpi/sleep.h b/drivers/acpi/sleep.h
> index 41675d24a9bc0..a495c91e2bf3b 100644
> --- a/drivers/acpi/sleep.h
> +++ b/drivers/acpi/sleep.h
> @@ -7,7 +7,7 @@ extern struct list_head acpi_wakeup_device_list;
> extern struct mutex acpi_device_lock;
>
> extern void acpi_resume_power_resources(void);
> -extern void acpi_turn_off_unused_power_resources(void);
> +extern void acpi_turn_off_power_resources(int acpi_system_state);
>
> static inline acpi_status acpi_set_waking_vector(u32 wakeup_address)
> {
> --
> 2.21.0.593.g511ec345e18-goog
>
Hi Rafael,
Gentle ping. Just checking if you got a chance to look at this one. It
is actually causing problems in one of our devices since power off
sequencing is not honored when entering S5.
Thanks,
Furquan
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