From: Rob Herring <robh@kernel.org>
Date: Thu, 20 Aug 2020 21:53:41 -0600
Subject: PCI: Allow root and child buses to have different pci_ops

Git-commit: 07e292950b9368518c659c4d5f1dca4bf55779bd
Patch-mainline: v5.10-rc1
References: bsc#1179344

PCI host bridges often have different ways to access the root and child
bus config spaces. The host bridge drivers have invented their own
abstractions to handle this. Let's support having different root and
child bus pci_ops so these per driver abstractions can be removed.

Link: https://lore.kernel.org/r/20200821035420.380495-2-robh@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
---
 drivers/pci/probe.c | 8 +++++++-
 include/linux/pci.h | 1 +
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 03d37128a24f..0c9ebc72532e 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1036,6 +1036,7 @@ static struct pci_bus *pci_alloc_child_bus(struct pci_bus *parent,
 					   struct pci_dev *bridge, int busnr)
 {
 	struct pci_bus *child;
+	struct pci_host_bridge *host;
 	int i;
 	int ret;
 
@@ -1045,11 +1046,16 @@ static struct pci_bus *pci_alloc_child_bus(struct pci_bus *parent,
 		return NULL;
 
 	child->parent = parent;
-	child->ops = parent->ops;
 	child->msi = parent->msi;
 	child->sysdata = parent->sysdata;
 	child->bus_flags = parent->bus_flags;
 
+	host = pci_find_host_bridge(parent);
+	if (host->child_ops)
+		child->ops = host->child_ops;
+	else
+		child->ops = parent->ops;
+
 	/*
 	 * Initialize some portions of the bus device, but don't register
 	 * it now as the parent is not properly set up yet.
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 835530605c0d..1fbe95a7d386 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -523,6 +523,7 @@ struct pci_host_bridge {
 	struct device	dev;
 	struct pci_bus	*bus;		/* Root bus */
 	struct pci_ops	*ops;
+	struct pci_ops	*child_ops;
 	void		*sysdata;
 	int		busnr;
 	struct list_head windows;	/* resource_entry */
-- 
2.26.2