linux-kernel - [PATCH v2 2/2] powerpc/pci: Prefer PCI domain assignment via DT 'linux,pci-domain' and alias

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Date:   Wed,  6 Jul 2022 12:21:48 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        "Guilherme G. Piccoli" <gpiccoli@...lia.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Guowen Shan <gshan@...hat.com>,
        Tyrel Datwyler <tyreld@...ux.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/2] powerpc/pci: Prefer PCI domain assignment via DT 'linux,pci-domain' and alias

Other Linux architectures use DT property 'linux,pci-domain' for specifying
fixed PCI domain of PCI controller specified in Device-Tree.

And lot of Freescale powerpc boards have defined numbered pci alias in
Device-Tree for every PCIe controller which number specify preferred PCI
domain.

So prefer usage of DT property 'linux,pci-domain' (via function
of_get_pci_domain_nr()) and DT pci alias (via function of_alias_get_id())
on powerpc architecture for assigning PCI domain to PCI controller.

Fixes: 63a72284b159 ("powerpc/pci: Assign fixed PHB number based on device-tree properties")
Signed-off-by: Pali Rohár <pali@...nel.org>
---
Changes in v2:
* New patch
---
 arch/powerpc/kernel/pci-common.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
index 7f959df34833..0715d74855b3 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c
@@ -78,10 +78,25 @@ static int get_phb_number(struct device_node *dn)
 
 	/*
 	 * Try fixed PHB numbering first, by checking archs and reading
-	 * the respective device-tree properties. Firstly, try powernv by
-	 * reading "ibm,opal-phbid", only present in OPAL environment.
+	 * the respective device-tree properties. Firstly, try reading
+	 * standard "linux,pci-domain", then try reading "ibm,opal-phbid"
+	 * (only present in powernv OPAL environment), then try device-tree
+	 * alias and as the last try to use lower bits of "reg" property
+	 * (only if CONFIG_PPC_PCI_DOMAIN_FROM_OF_REG is enabled).
 	 */
-	ret = of_property_read_u64(dn, "ibm,opal-phbid", &prop);
+	ret = of_get_pci_domain_nr(dn);
+	if (ret >= 0) {
+		prop = ret;
+		ret = 0;
+	}
+	if (ret)
+		ret = of_property_read_u64(dn, "ibm,opal-phbid", &prop);
+	if (ret)
+		ret = of_alias_get_id(dn, "pci");
+	if (ret >= 0) {
+		prop = ret;
+		ret = 0;
+	}
 	if (ret && IS_ENABLED(CONFIG_PPC_PCI_DOMAIN_FROM_OF_REG)) {
 		u32 prop_32;
 		ret = of_property_read_u32_index(dn, "reg", 1, &prop_32);
@@ -95,10 +110,7 @@ static int get_phb_number(struct device_node *dn)
 	if ((phb_id >= 0) && !test_and_set_bit(phb_id, phb_bitmap))
 		return phb_id;
 
-	/*
-	 * If not pseries nor powernv, or if fixed PHB numbering tried to add
-	 * the same PHB number twice, then fallback to dynamic PHB numbering.
-	 */
+	/* If everything fails then fallback to dynamic PHB numbering. */
 	phb_id = find_first_zero_bit(phb_bitmap, MAX_PHBS);
 	BUG_ON(phb_id >= MAX_PHBS);
 	set_bit(phb_id, phb_bitmap);
-- 
2.20.1