FROMLIST: PCI: Prevent LS7A Bus Master clearing on kexec

This is similar to commit 62b6dee ("PCI/portdrv: Prevent LS7A Bus
Master clearing on shutdown"), which prevents LS7A Bus Master clearing
on kexec.

The key point of this is to work around the LS7A defect that clearing
PCI_COMMAND_MASTER prevents MMIO requests from going downstream, and
we may need to do that even after .shutdown(), e.g., to print console
messages. And in this case we rely on .shutdown() for the downstream
devices to disable interrupts and DMA.

Only skip Bus Master clearing on bridges because endpoint devices still
need it.

Cc: [email protected]
Signed-off-by: Ming Wang <[email protected]>
Signed-off-by: Huacai Chen <[email protected]>

Link: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Kexy Biscuit <[email protected]>

Author: chenhuacai

drivers/pci/pci-driver.c

@@ -517,7 +517,7 @@ static void pci_device_shutdown(struct device *dev)
 	 * If it is not a kexec reboot, firmware will hit the PCI
 	 * devices with big hammer and stop their DMA any way.
 	 */
-	if (kexec_in_progress && (pci_dev->current_state <= PCI_D3hot))
+	if (kexec_in_progress && !pci_is_bridge(pci_dev) && (pci_dev->current_state <= PCI_D3hot))
 		pci_clear_master(pci_dev);
 }