[PATCH v2 1/2] bus: mhi: pci_generic: Prevent MHI from aborting system suspend

[Len Brown <lenb@kernel.org>]

From: Len Brown <len.brown@intel.com>

mhi sometimes aborts system suspend on the thinkpad T16 gen3:

mhi-pci-generic 0000:08:00.0:
... failed to suspend device: -16
... PM: pci_pm_suspend(): mhi_pci_suspend [mhi_pci_generic] returns -16
... PM: dpm_run_callback(): pci_pm_suspend returns -16
... PM: pci_pm_suspend returned -16 after 15145 usecs
... PM: failed to suspend async: error -16

Prevent MHI from spreading this device-specific failure
to the rest of the system.  I.e. "Why is a modem that I don't use
preventing me from suspending my laptop?"

This change does not comprehend the internal root cause of the
mhi failure, which should be found and fixed.

There is also a risk that ignoring the MHI error and continuing
to put the device into PCI D3 will leave it in an error state.

Fixes: d3800c1dce24 ("bus: mhi: pci_generic: Add support for runtime PM")
Signed-off-by: Len Brown <len.brown@intel.com>
---
 drivers/bus/mhi/host/pci_generic.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/bus/mhi/host/pci_generic.c b/drivers/bus/mhi/host/pci_generic.c
index 7193a384cca4..343d1046a25e 100644
--- a/drivers/bus/mhi/host/pci_generic.c
+++ b/drivers/bus/mhi/host/pci_generic.c
@@ -1727,7 +1727,12 @@ static int __maybe_unused mhi_pci_runtime_resume(struct device *dev)
 static int  __maybe_unused mhi_pci_suspend(struct device *dev)
 {
 	pm_runtime_disable(dev);
-	return mhi_pci_runtime_suspend(dev);
+
+	/* Ignore errors (e.g. -EBUSY); a failed modem suspend must not abort system suspend */
+	mhi_pci_runtime_suspend(dev);
+
+	/* Must return 0 to allow system suspend to continue */
+	return 0;
 }
 
 static int __maybe_unused mhi_pci_resume(struct device *dev)
-- 
2.45.2