Re: [PATCH v2] bus: mhi: host: pci_generic: Add missing poweroff() PM callback

From: Bhaumik Vasav Bhatt
Date: Tue Apr 05 2022 - 22:27:20 EST

On 4/5/2022 5:59 AM, Manivannan Sadhasivam wrote:
During hibernation process, once thaw() stage completes, the MHI endpoint
devices will be in M0 state post recovery. After that, the devices will be
powered down so that the system can enter the target sleep state. During
this stage, the PCI core will put the devices in D3hot. But this transition
is allowed by the MHI spec. The devices can only enter D3hot when it is in
M3 state.

So for fixing this issue, let's add the poweroff() callback that will get
executed before putting the system in target sleep state during
hibernation. This callback will power down the device properly so that it
could be restored during restore() or thaw() stage.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 5f0c2ee1fe8d ("bus: mhi: pci-generic: Fix hibernation")
Reported-by: Hemant Kumar <quic_hemantk@xxxxxxxxxxx>
Suggested-by: Hemant Kumar <quic_hemantk@xxxxxxxxxxx>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>

Changes in v2:

* Hemant suggested to use restore function for poweroff() callback as we can
make sure that the device gets powered down properly.

drivers/bus/mhi/host/pci_generic.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/bus/mhi/host/pci_generic.c b/drivers/bus/mhi/host/pci_generic.c
index 9527b7d63840..ef85dbfb3216 100644
--- a/drivers/bus/mhi/host/pci_generic.c
+++ b/drivers/bus/mhi/host/pci_generic.c
@@ -1085,6 +1085,7 @@ static const struct dev_pm_ops mhi_pci_pm_ops = {
.resume = mhi_pci_resume,
.freeze = mhi_pci_freeze,
.thaw = mhi_pci_restore,
+ .poweroff = mhi_pci_freeze,

It is possible that .thaw() queues recovery work and recovery work is still running

while .poweroff() is called. I would suggest adding a flush_work() in freeze such that

we don't try to power off while we're also trying to power on MHI from recovery work.

.restore = mhi_pci_restore,