diff mbox series

[v4,4/7] pmdomain: core: Introduce dev_pm_genpd_rpm_always_on()

Message ID 1730705521-23081-5-git-send-email-shawn.lin@rock-chips.com (mailing list archive)
State New
Headers show
Series Initial support for RK3576 UFS controller | expand

Commit Message

Shawn Lin Nov. 4, 2024, 7:31 a.m. UTC 
From: Ulf Hansson <ulf.hansson@linaro.org>

For some usecases a consumer driver requires its device to remain power-on
from the PM domain perspective during runtime. Using dev PM qos along with
the genpd governors, doesn't work for this case as would potentially
prevent the device from being runtime suspended too.

To support these usecases, let's introduce dev_pm_genpd_rpm_always_on() to
allow consumers drivers to dynamically control the behaviour in genpd for a
device that is attached to it.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---

Changes in v4: None
Changes in v3: None
Changes in v2: None

 drivers/pmdomain/core.c   | 34 ++++++++++++++++++++++++++++++++++
 include/linux/pm_domain.h |  7 +++++++
 2 files changed, 41 insertions(+)

Comments

kernel test robot Nov. 4, 2024, 7:04 p.m. UTC | #1 
Hi Shawn,

kernel test robot noticed the following build warnings:

[auto build test WARNING on jejb-scsi/for-next]
[also build test WARNING on robh/for-next linus/master v6.12-rc6]
[cannot apply to mkp-scsi/for-next next-20241104]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Shawn-Lin/dt-bindings-ufs-Document-Rockchip-UFS-host-controller/20241104-191810
base:   https://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi.git for-next
patch link:    https://lore.kernel.org/r/1730705521-23081-5-git-send-email-shawn.lin%40rock-chips.com
patch subject: [PATCH v4 4/7] pmdomain: core: Introduce dev_pm_genpd_rpm_always_on()
config: x86_64-buildonly-randconfig-003-20241104 (https://download.01.org/0day-ci/archive/20241105/202411050203.kPDzy0bS-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-12) 11.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241105/202411050203.kPDzy0bS-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202411050203.kPDzy0bS-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/pmdomain/core.c: In function 'genpd_power_off':
>> drivers/pmdomain/core.c:893:17: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
     893 |                 if (!pm_runtime_suspended(pdd->dev) ||
         |                 ^~
   drivers/pmdomain/core.c:898:25: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
     898 |                         if (to_gpd_data(pdd)->rpm_always_on)
         |                         ^~


vim +/if +893 drivers/pmdomain/core.c

29e47e2173349e drivers/base/power/domain.c Ulf Hansson     2015-09-02  837  
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  838  /**
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  839   * genpd_power_off - Remove power from a given PM domain.
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  840   * @genpd: PM domain to power down.
3c64649d1cf9f3 drivers/base/power/domain.c Ulf Hansson     2017-02-17  841   * @one_dev_on: If invoked from genpd's ->runtime_suspend|resume() callback, the
3c64649d1cf9f3 drivers/base/power/domain.c Ulf Hansson     2017-02-17  842   * RPM status of the releated device is in an intermediate state, not yet turned
3c64649d1cf9f3 drivers/base/power/domain.c Ulf Hansson     2017-02-17  843   * into RPM_SUSPENDED. This means genpd_power_off() must allow one device to not
3c64649d1cf9f3 drivers/base/power/domain.c Ulf Hansson     2017-02-17  844   * be RPM_SUSPENDED, while it tries to power off the PM domain.
763663c9715f5f drivers/base/power/domain.c Yang Yingliang  2021-05-12  845   * @depth: nesting count for lockdep.
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  846   *
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  847   * If all of the @genpd's devices have been suspended and all of its subdomains
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  848   * have been powered down, remove power from @genpd.
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  849   */
2da835452a0875 drivers/base/power/domain.c Ulf Hansson     2017-02-17  850  static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
2da835452a0875 drivers/base/power/domain.c Ulf Hansson     2017-02-17  851  			   unsigned int depth)
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  852  {
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  853  	struct pm_domain_data *pdd;
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  854  	struct gpd_link *link;
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  855  	unsigned int not_suspended = 0;
f63816e43d9044 drivers/base/power/domain.c Ulf Hansson     2020-09-24  856  	int ret;
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  857  
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  858  	/*
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  859  	 * Do not try to power off the domain in the following situations:
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  860  	 * (1) The domain is already in the "power off" state.
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  861  	 * (2) System suspend is in progress.
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  862  	 */
41e2c8e0060db2 drivers/base/power/domain.c Ulf Hansson     2017-03-20  863  	if (!genpd_status_on(genpd) || genpd->prepared_count > 0)
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  864  		return 0;
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  865  
ffaa42e8a40b7f drivers/base/power/domain.c Ulf Hansson     2017-03-20  866  	/*
ffaa42e8a40b7f drivers/base/power/domain.c Ulf Hansson     2017-03-20  867  	 * Abort power off for the PM domain in the following situations:
ffaa42e8a40b7f drivers/base/power/domain.c Ulf Hansson     2017-03-20  868  	 * (1) The domain is configured as always on.
ffaa42e8a40b7f drivers/base/power/domain.c Ulf Hansson     2017-03-20  869  	 * (2) When the domain has a subdomain being powered on.
ffaa42e8a40b7f drivers/base/power/domain.c Ulf Hansson     2017-03-20  870  	 */
ed61e18a4b4e44 drivers/base/power/domain.c Leonard Crestez 2019-04-30  871  	if (genpd_is_always_on(genpd) ||
ed61e18a4b4e44 drivers/base/power/domain.c Leonard Crestez 2019-04-30  872  			genpd_is_rpm_always_on(genpd) ||
ed61e18a4b4e44 drivers/base/power/domain.c Leonard Crestez 2019-04-30  873  			atomic_read(&genpd->sd_count) > 0)
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  874  		return -EBUSY;
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  875  
e7d90cfac5510f drivers/base/power/domain.c Ulf Hansson     2022-02-17  876  	/*
e7d90cfac5510f drivers/base/power/domain.c Ulf Hansson     2022-02-17  877  	 * The children must be in their deepest (powered-off) states to allow
e7d90cfac5510f drivers/base/power/domain.c Ulf Hansson     2022-02-17  878  	 * the parent to be powered off. Note that, there's no need for
e7d90cfac5510f drivers/base/power/domain.c Ulf Hansson     2022-02-17  879  	 * additional locking, as powering on a child, requires the parent's
e7d90cfac5510f drivers/base/power/domain.c Ulf Hansson     2022-02-17  880  	 * lock to be acquired first.
e7d90cfac5510f drivers/base/power/domain.c Ulf Hansson     2022-02-17  881  	 */
e7d90cfac5510f drivers/base/power/domain.c Ulf Hansson     2022-02-17  882  	list_for_each_entry(link, &genpd->parent_links, parent_node) {
e7d90cfac5510f drivers/base/power/domain.c Ulf Hansson     2022-02-17  883  		struct generic_pm_domain *child = link->child;
e7d90cfac5510f drivers/base/power/domain.c Ulf Hansson     2022-02-17  884  		if (child->state_idx < child->state_count - 1)
e7d90cfac5510f drivers/base/power/domain.c Ulf Hansson     2022-02-17  885  			return -EBUSY;
e7d90cfac5510f drivers/base/power/domain.c Ulf Hansson     2022-02-17  886  	}
e7d90cfac5510f drivers/base/power/domain.c Ulf Hansson     2022-02-17  887  
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  888  	list_for_each_entry(pdd, &genpd->dev_list, list_node) {
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  889  		/*
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  890  		 * Do not allow PM domain to be powered off, when an IRQ safe
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  891  		 * device is part of a non-IRQ safe domain.
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  892  		 */
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17 @893  		if (!pm_runtime_suspended(pdd->dev) ||
7a02444b8fc25a drivers/base/power/domain.c Ulf Hansson     2022-05-11  894  			irq_safe_dev_in_sleep_domain(pdd->dev, genpd))
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  895  			not_suspended++;
f0f6da10152fb8 drivers/pmdomain/core.c     Ulf Hansson     2024-11-04  896  
f0f6da10152fb8 drivers/pmdomain/core.c     Ulf Hansson     2024-11-04  897  			/* The device may need its PM domain to stay powered on. */
f0f6da10152fb8 drivers/pmdomain/core.c     Ulf Hansson     2024-11-04  898  			if (to_gpd_data(pdd)->rpm_always_on)
f0f6da10152fb8 drivers/pmdomain/core.c     Ulf Hansson     2024-11-04  899  				return -EBUSY;
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  900  	}
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  901  
3c64649d1cf9f3 drivers/base/power/domain.c Ulf Hansson     2017-02-17  902  	if (not_suspended > 1 || (not_suspended == 1 && !one_dev_on))
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  903  		return -EBUSY;
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  904  
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  905  	if (genpd->gov && genpd->gov->power_down_ok) {
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  906  		if (!genpd->gov->power_down_ok(&genpd->domain))
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  907  			return -EAGAIN;
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  908  	}
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  909  
2c9b7f8772033c drivers/base/power/domain.c Ulf Hansson     2018-10-03  910  	/* Default to shallowest state. */
2c9b7f8772033c drivers/base/power/domain.c Ulf Hansson     2018-10-03  911  	if (!genpd->gov)
2c9b7f8772033c drivers/base/power/domain.c Ulf Hansson     2018-10-03  912  		genpd->state_idx = 0;
2c9b7f8772033c drivers/base/power/domain.c Ulf Hansson     2018-10-03  913  
f63816e43d9044 drivers/base/power/domain.c Ulf Hansson     2020-09-24  914  	/* Don't power off, if a child domain is waiting to power on. */
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  915  	if (atomic_read(&genpd->sd_count) > 0)
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  916  		return -EBUSY;
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  917  
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  918  	ret = _genpd_power_off(genpd, true);
c6a113b52302ad drivers/base/power/domain.c Lina Iyer       2020-10-15  919  	if (ret) {
c6a113b52302ad drivers/base/power/domain.c Lina Iyer       2020-10-15  920  		genpd->states[genpd->state_idx].rejected++;
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  921  		return ret;
c6a113b52302ad drivers/base/power/domain.c Lina Iyer       2020-10-15  922  	}
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  923  
49f618e1b669ef drivers/base/power/domain.c Ulf Hansson     2020-09-24  924  	genpd->status = GENPD_STATE_OFF;
afece3ab9a3640 drivers/base/power/domain.c Thara Gopinath  2017-07-14  925  	genpd_update_accounting(genpd);
c6a113b52302ad drivers/base/power/domain.c Lina Iyer       2020-10-15  926  	genpd->states[genpd->state_idx].usage++;
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  927  
8d87ae48ced2df drivers/base/power/domain.c Kees Cook       2020-07-08  928  	list_for_each_entry(link, &genpd->child_links, child_node) {
8d87ae48ced2df drivers/base/power/domain.c Kees Cook       2020-07-08  929  		genpd_sd_counter_dec(link->parent);
8d87ae48ced2df drivers/base/power/domain.c Kees Cook       2020-07-08  930  		genpd_lock_nested(link->parent, depth + 1);
8d87ae48ced2df drivers/base/power/domain.c Kees Cook       2020-07-08  931  		genpd_power_off(link->parent, false, depth + 1);
8d87ae48ced2df drivers/base/power/domain.c Kees Cook       2020-07-08  932  		genpd_unlock(link->parent);
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  933  	}
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  934  
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  935  	return 0;
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  936  }
1f8728b7adc4c2 drivers/base/power/domain.c Ulf Hansson     2017-02-17  937
kernel test robot Nov. 4, 2024, 8:17 p.m. UTC | #2 
Hi Shawn,

kernel test robot noticed the following build warnings:

[auto build test WARNING on jejb-scsi/for-next]
[also build test WARNING on robh/for-next linus/master v6.12-rc6]
[cannot apply to mkp-scsi/for-next next-20241104]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Shawn-Lin/dt-bindings-ufs-Document-Rockchip-UFS-host-controller/20241104-191810
base:   https://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi.git for-next
patch link:    https://lore.kernel.org/r/1730705521-23081-5-git-send-email-shawn.lin%40rock-chips.com
patch subject: [PATCH v4 4/7] pmdomain: core: Introduce dev_pm_genpd_rpm_always_on()
config: x86_64-buildonly-randconfig-002-20241104 (https://download.01.org/0day-ci/archive/20241105/202411050317.abJatSkD-lkp@intel.com/config)
compiler: clang version 19.1.3 (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b254b6afab99)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241105/202411050317.abJatSkD-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202411050317.abJatSkD-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from drivers/pmdomain/core.c:21:
   In file included from include/linux/suspend.h:5:
   In file included from include/linux/swap.h:9:
   In file included from include/linux/memcontrol.h:21:
   In file included from include/linux/mm.h:2213:
   include/linux/vmstat.h:518:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
     518 |         return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
         |                               ~~~~~~~~~~~ ^ ~~~
>> drivers/pmdomain/core.c:898:4: warning: misleading indentation; statement is not part of the previous 'if' [-Wmisleading-indentation]
     898 |                         if (to_gpd_data(pdd)->rpm_always_on)
         |                         ^
   drivers/pmdomain/core.c:893:3: note: previous statement is here
     893 |                 if (!pm_runtime_suspended(pdd->dev) ||
         |                 ^
   2 warnings generated.


vim +/if +898 drivers/pmdomain/core.c

   837	
   838	/**
   839	 * genpd_power_off - Remove power from a given PM domain.
   840	 * @genpd: PM domain to power down.
   841	 * @one_dev_on: If invoked from genpd's ->runtime_suspend|resume() callback, the
   842	 * RPM status of the releated device is in an intermediate state, not yet turned
   843	 * into RPM_SUSPENDED. This means genpd_power_off() must allow one device to not
   844	 * be RPM_SUSPENDED, while it tries to power off the PM domain.
   845	 * @depth: nesting count for lockdep.
   846	 *
   847	 * If all of the @genpd's devices have been suspended and all of its subdomains
   848	 * have been powered down, remove power from @genpd.
   849	 */
   850	static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
   851				   unsigned int depth)
   852	{
   853		struct pm_domain_data *pdd;
   854		struct gpd_link *link;
   855		unsigned int not_suspended = 0;
   856		int ret;
   857	
   858		/*
   859		 * Do not try to power off the domain in the following situations:
   860		 * (1) The domain is already in the "power off" state.
   861		 * (2) System suspend is in progress.
   862		 */
   863		if (!genpd_status_on(genpd) || genpd->prepared_count > 0)
   864			return 0;
   865	
   866		/*
   867		 * Abort power off for the PM domain in the following situations:
   868		 * (1) The domain is configured as always on.
   869		 * (2) When the domain has a subdomain being powered on.
   870		 */
   871		if (genpd_is_always_on(genpd) ||
   872				genpd_is_rpm_always_on(genpd) ||
   873				atomic_read(&genpd->sd_count) > 0)
   874			return -EBUSY;
   875	
   876		/*
   877		 * The children must be in their deepest (powered-off) states to allow
   878		 * the parent to be powered off. Note that, there's no need for
   879		 * additional locking, as powering on a child, requires the parent's
   880		 * lock to be acquired first.
   881		 */
   882		list_for_each_entry(link, &genpd->parent_links, parent_node) {
   883			struct generic_pm_domain *child = link->child;
   884			if (child->state_idx < child->state_count - 1)
   885				return -EBUSY;
   886		}
   887	
   888		list_for_each_entry(pdd, &genpd->dev_list, list_node) {
   889			/*
   890			 * Do not allow PM domain to be powered off, when an IRQ safe
   891			 * device is part of a non-IRQ safe domain.
   892			 */
   893			if (!pm_runtime_suspended(pdd->dev) ||
   894				irq_safe_dev_in_sleep_domain(pdd->dev, genpd))
   895				not_suspended++;
   896	
   897				/* The device may need its PM domain to stay powered on. */
 > 898				if (to_gpd_data(pdd)->rpm_always_on)
   899					return -EBUSY;
   900		}
   901	
   902		if (not_suspended > 1 || (not_suspended == 1 && !one_dev_on))
   903			return -EBUSY;
   904	
   905		if (genpd->gov && genpd->gov->power_down_ok) {
   906			if (!genpd->gov->power_down_ok(&genpd->domain))
   907				return -EAGAIN;
   908		}
   909	
   910		/* Default to shallowest state. */
   911		if (!genpd->gov)
   912			genpd->state_idx = 0;
   913	
   914		/* Don't power off, if a child domain is waiting to power on. */
   915		if (atomic_read(&genpd->sd_count) > 0)
   916			return -EBUSY;
   917	
   918		ret = _genpd_power_off(genpd, true);
   919		if (ret) {
   920			genpd->states[genpd->state_idx].rejected++;
   921			return ret;
   922		}
   923	
   924		genpd->status = GENPD_STATE_OFF;
   925		genpd_update_accounting(genpd);
   926		genpd->states[genpd->state_idx].usage++;
   927	
   928		list_for_each_entry(link, &genpd->child_links, child_node) {
   929			genpd_sd_counter_dec(link->parent);
   930			genpd_lock_nested(link->parent, depth + 1);
   931			genpd_power_off(link->parent, false, depth + 1);
   932			genpd_unlock(link->parent);
   933		}
   934	
   935		return 0;
   936	}
   937
diff mbox series

Patch

diff --git a/drivers/pmdomain/core.c b/drivers/pmdomain/core.c
index 5ede0f7..02bb5c8 100644
--- a/drivers/pmdomain/core.c
+++ b/drivers/pmdomain/core.c
@@ -692,6 +692,36 @@  bool dev_pm_genpd_get_hwmode(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(dev_pm_genpd_get_hwmode);
 
+/**
+ * dev_pm_genpd_rpm_always_on() - Control if the PM domain can be powered off.
+ *
+ * @dev: Device for which the PM domain may need to stay on for.
+ * @on: Value to set or unset for the condition.
+ *
+ * For some usecases a consumer driver requires its device to remain power-on
+ * from the PM domain perspective during runtime. This function allows the
+ * behaviour to be dynamically controlled for a device attached to a genpd.
+ *
+ * It is assumed that the users guarantee that the genpd wouldn't be detached
+ * while this routine is getting called.
+ *
+ * Return: Returns 0 on success and negative error values on failures.
+ */
+int dev_pm_genpd_rpm_always_on(struct device *dev, bool on)
+{
+	struct generic_pm_domain *genpd;
+
+	genpd = dev_to_genpd_safe(dev);
+	if (!genpd)
+		return -ENODEV;
+
+	genpd_lock(genpd);
+	dev_gpd_data(dev)->rpm_always_on = on;
+	genpd_unlock(genpd);
+
+	return 0;
+}
+
 static int _genpd_power_on(struct generic_pm_domain *genpd, bool timed)
 {
 	unsigned int state_idx = genpd->state_idx;
@@ -863,6 +893,10 @@  static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
 		if (!pm_runtime_suspended(pdd->dev) ||
 			irq_safe_dev_in_sleep_domain(pdd->dev, genpd))
 			not_suspended++;
+
+			/* The device may need its PM domain to stay powered on. */
+			if (to_gpd_data(pdd)->rpm_always_on)
+				return -EBUSY;
 	}
 
 	if (not_suspended > 1 || (not_suspended == 1 && !one_dev_on))
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index b637ec1..30186ad 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -245,6 +245,7 @@  struct generic_pm_domain_data {
 	unsigned int default_pstate;
 	unsigned int rpm_pstate;
 	bool hw_mode;
+	bool rpm_always_on;
 	void *data;
 };
 
@@ -277,6 +278,7 @@  ktime_t dev_pm_genpd_get_next_hrtimer(struct device *dev);
 void dev_pm_genpd_synced_poweroff(struct device *dev);
 int dev_pm_genpd_set_hwmode(struct device *dev, bool enable);
 bool dev_pm_genpd_get_hwmode(struct device *dev);
+int dev_pm_genpd_rpm_always_on(struct device *dev, bool on);
 
 extern struct dev_power_governor simple_qos_governor;
 extern struct dev_power_governor pm_domain_always_on_gov;
@@ -360,6 +362,11 @@  static inline bool dev_pm_genpd_get_hwmode(struct device *dev)
 	return false;
 }
 
+static inline int dev_pm_genpd_rpm_always_on(struct device *dev, bool on)
+{
+	return -EOPNOTSUPP;
+}
+
 #define simple_qos_governor		(*(struct dev_power_governor *)(NULL))
 #define pm_domain_always_on_gov		(*(struct dev_power_governor *)(NULL))
 #endif