[PATCH v2 02/12] arm_mpam: Restore the error interrupt enable from mpam_cpu_online()

[Ben Horgan <ben.horgan@arm.com>]

When all the associated CPUs to an MSC are offline, possibly caused by
PSCI_CPU_OFF, the power supply to the MSC can be cut off and all the
registers that are unknown out of reset, including MPAMF_ECR.INTEN, are
lost. Afterwards, we need to explicitly set MPAMF_ECR.INTEN when the first
associated CPU becomes online and the power supply to the MSC is recovered.

Restore MPAMF_ECR.INTEN in mpam_cpu_online() when the first associated CPU
of the MSC becomes online.

Fixes: 49aa621c4dca ("arm_mpam: Register and enable IRQs")
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Tested-by: Gavin Shan <gshan@redhat.com>
---
Changes since v1:
Update the commit message (Gavin)
---
 drivers/resctrl/mpam_devices.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 580d7ed38569..32bde94dfbc3 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -1856,8 +1856,14 @@ static int mpam_cpu_online(unsigned int cpu)
 		if (msc->reenable_error_ppi)
 			_enable_percpu_irq(&msc->reenable_error_ppi);
 
-		if (atomic_fetch_inc(&msc->online_refs) == 0)
+		if (atomic_fetch_inc(&msc->online_refs) == 0) {
+			mutex_lock(&msc->error_irq_lock);
+			if (msc->error_irq_hw_enabled)
+				mpam_touch_msc(msc, mpam_enable_msc_ecr, msc);
+			mutex_unlock(&msc->error_irq_lock);
+
 			mpam_reprogram_msc(msc);
+		}
 	}
 
 	if (mpam_resctrl_enabled)
-- 
2.43.0