Hi reviewers,

I suggest to backport commit "887371066039011144b4a94af97d9328df6869a2 PM: runtime: Fix supplier device management during consumer probe" to linux-5.15 tree.

This patch fix device link of runtime pm issue.

commit: 887371066039011144b4a94af97d9328df6869a2 subject: PM: runtime: Fix supplier device management during consumer probe

Thanks. BR Peter

-----Original Message----- From: gregkh@linuxfoundation.org gregkh@linuxfoundation.org Sent: Saturday, July 9, 2022 4:22 PM To: rafael.j.wysocki@intel.com; gregkh@linuxfoundation.org; Peter Wang (王信友) peter.wang@mediatek.com; stable@vger.kernel.org Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] PM: runtime: Fix supplier device management during consumer" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 887371066039011144b4a94af97d9328df6869a2 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" rafael.j.wysocki@intel.com Date: Thu, 30 Jun 2022 21:16:41 +0200 Subject: [PATCH] PM: runtime: Fix supplier device management during consumer probe

Because pm_runtime_get_suppliers() bumps up the rpm_active counter of each device link to a supplier of the given device in addition to bumping up the supplier's PM-runtime usage counter, a runtime suspend of the consumer device may case the latter to go down to 0 when pm_runtime_put_suppliers() is running on a remote CPU. If that happens after pm_runtime_put_suppliers() has released power.lock for the consumer device, and a runtime resume of that device takes place immediately after it, before pm_runtime_put() is called for the supplier, that pm_runtime_put() call may cause the supplier to be suspended even though the consumer is active.

To prevent that from happening, modify pm_runtime_get_suppliers() to call pm_runtime_get_sync() for the given device's suppliers without touching the rpm_active counters of the involved device links Accordingly, modify pm_runtime_put_suppliers() to call pm_runtime_put() for the given device's suppliers without looking at the rpm_active counters of the device links at hand. [This is analogous to what happened before commit 4c06c4e6cf63 ("driver core: Fix possible supplier PM-usage counter imbalance").]

Since pm_runtime_get_suppliers() sets supplier_preactivated for each device link where the supplier's PM-runtime usage counter has been incremented and pm_runtime_put_suppliers() calls pm_runtime_put() for the suppliers whose device links have supplier_preactivated set, the PM-runtime usage counter is balanced for each supplier and this is independent of the runtime suspend and resume of the consumer device.

However, in case a device link with DL_FLAG_PM_RUNTIME set is dropped during the consumer device probe, so pm_runtime_get_suppliers() bumps up the supplier's PM-runtime usage counter, but it cannot be dropped by pm_runtime_put_suppliers(), make device_link_release_fn() take care of that.

Fixes: 4c06c4e6cf63 ("driver core: Fix possible supplier PM-usage counter imbalance") Reported-by: Peter Wang peter.wang@mediatek.com Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Reviewed-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Reviewed-by: Peter Wang peter.wang@mediatek.com Cc: 5.1+ stable@vger.kernel.org # 5.1+

diff --git a/drivers/base/core.c b/drivers/base/core.c index 58aa49527d3a..460d6f163e41 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -487,6 +487,16 @@ static void device_link_release_fn(struct work_struct *work) device_link_synchronize_removal();

pm_runtime_release_supplier(link); + /* + * If supplier_preactivated is set, the link has been dropped between + * the pm_runtime_get_suppliers() and pm_runtime_put_suppliers() calls + * in __driver_probe_device(). In that case, drop the supplier's + * PM-runtime usage counter to remove the reference taken by + * pm_runtime_get_suppliers(). + */ + if (link->supplier_preactivated) + pm_runtime_put_noidle(link->supplier); + pm_request_idle(link->supplier);

put_device(link->consumer); diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 23cc4c377d77..949907e2e242 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -1768,7 +1768,6 @@ void pm_runtime_get_suppliers(struct device *dev) if (link->flags & DL_FLAG_PM_RUNTIME) { link->supplier_preactivated = true; pm_runtime_get_sync(link->supplier); - refcount_inc(&link->rpm_active); }

device_links_read_unlock(idx); @@ -1788,19 +1787,8 @@ void pm_runtime_put_suppliers(struct device *dev) list_for_each_entry_rcu(link, &dev->links.suppliers, c_node, device_links_read_lock_held()) if (link->supplier_preactivated) { - bool put; - link->supplier_preactivated = false; - - spin_lock_irq(&dev->power.lock); - - put = pm_runtime_status_suspended(dev) && - refcount_dec_not_one(&link->rpm_active); - - spin_unlock_irq(&dev->power.lock); - - if (put) - pm_runtime_put(link->supplier); + pm_runtime_put(link->supplier); }

device_links_read_unlock(idx);