[RFC PATCH] Let device drivers disable msi on shutdown

[Keith Busch <keith.busch@intel.com>]

I'd like to do shutdowns asynchronously so I can shutdown multiple
devices in parallel, but the pci-driver disables interrupts after my
driver returns from its '.shutdown', though it needs to rely on these
interrupts in its asynchronously scheduled shutdown.

I tracked the reason for pci disabling msi to ...

| commit d52877c7b1afb8c37ebe17e2005040b79cb618b0
| Author: Yinghai Lu <yhlu.kernel.send@gmail.com>
| Date:   Wed Apr 23 14:58:09 2008 -0700
|
|     pci/irq: let pci_device_shutdown to call pci_msi_shutdown v2

... because mptfusion doesn't disable msi in its shutdown path.

Any reason we can't let the drivers do this instead?

To provide context why I want to do this asynchronously, NVM-Express has
one PCI device per controller, of which there could be dozens in a system,
and each one may take many seconds (I've heard over ten in some cases)
to safely shutdown.

In this patch, mptfusion was compile tested only; I didn't observe any
adverse affects from running the pci portion.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Cc: Nagalakshmi Nandigama <Nagalakshmi.Nandigama@lsi.com>
Cc: Sreekanth Reddy <Sreekanth.Reddy@lsi.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
---
 drivers/message/fusion/mptscsih.c |    3 +++
 drivers/pci/pci-driver.c          |    2 --
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/message/fusion/mptscsih.c b/drivers/message/fusion/mptscsih.c
index 2a1c6f2..3186e17 100644
--- a/drivers/message/fusion/mptscsih.c
+++ b/drivers/message/fusion/mptscsih.c
@@ -1215,6 +1215,9 @@ mptscsih_remove(struct pci_dev *pdev)
 void
 mptscsih_shutdown(struct pci_dev *pdev)
 {
+	MPT_ADAPTER *ioc = pci_get_drvdata(pdev);
+	if (ioc->msi_enable)
+		pci_disable_msi(pdev);
 }
 
 #ifdef CONFIG_PM
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 3f8e3db..8079d98 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -453,8 +453,6 @@ static void pci_device_shutdown(struct device *dev)
 
 	if (drv && drv->shutdown)
 		drv->shutdown(pci_dev);
-	pci_msi_shutdown(pci_dev);
-	pci_msix_shutdown(pci_dev);
 
 #ifdef CONFIG_KEXEC
 	/*
-- 
1.7.10.4