linux-kernel - [v3 PATCH 1/2] PCI: read fixed bus numbers in EA for type 1 functions

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Message-Id: <1548249481-24645-1-git-send-email-sundeep.lkml@gmail.com>
Date:   Wed, 23 Jan 2019 18:48:00 +0530
From:   sundeep.lkml@...il.com
To:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     sean.stalley@...el.com, sgoutham@...vell.com, helgaas@...nel.org,
        Subbaraya Sundeep <sbhatta@...vell.com>
Subject: [v3 PATCH 1/2] PCI: read fixed bus numbers in EA for type 1 functions

From: Subbaraya Sundeep <sbhatta@...vell.com>

As per the spec - ECN_Enhanced_Allocation_23_Oct_2014_Final
and section 6.9.1.2, EA capability contains fixed secondary
and subordinate bus numbers for type 1 functions.
This patch adds support to read the fixed bus numbers
from EA capability for bridge.

Signed-off-by: Subbaraya Sundeep <sbhatta@...vell.com>
---
v3:
  As per Bjorn's suggestion placed EA stuff in pci_ea_init and
  captured bus numbers in pci_dev
v2:
  None just added Sean

 drivers/pci/pci.c             | 10 ++++++++--
 include/linux/pci.h           |  4 ++++
 include/uapi/linux/pci_regs.h |  4 ++++
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index c25acac..484b63e 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2909,6 +2909,7 @@ void pci_ea_init(struct pci_dev *dev)
 	u8 num_ent;
 	int offset;
 	int i;
+	u32 dw;
 
 	/* find PCI EA capability in list */
 	ea = pci_find_capability(dev, PCI_CAP_ID_EA);
@@ -2922,9 +2923,14 @@ void pci_ea_init(struct pci_dev *dev)
 
 	offset = ea + PCI_EA_FIRST_ENT;
 
-	/* Skip DWORD 2 for type 1 functions */
-	if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE)
+	/* Note fixed bus numbers for type 1 functions */
+	if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
+		pci_read_config_dword(dev, offset, &dw);
+		dev->fixed_sec_busnr = dw & PCI_EA_FIXED_SEC_BUS;
+		dev->fixed_sub_busnr = (dw & PCI_EA_FIXED_SUB_BUS) >>
+					PCI_EA_FIXED_SUB_SHIFT;
 		offset += 4;
+	}
 
 	/* parse each EA entry */
 	for (i = 0; i < num_ent; ++i)
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 65f1d8c..3e9a3ae 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -459,6 +459,10 @@ struct pci_dev {
 	char		*driver_override; /* Driver name to force a match */
 
 	unsigned long	priv_flags;	/* Private flags for the PCI driver */
+
+	/* bus numbers from EA capability if this device is a bridge */
+	u8 fixed_sec_busnr; /* Fixed Secondary Bus number */
+	u8 fixed_sub_busnr; /* Fixed Subordinate Bus number */
 };
 
 static inline struct pci_dev *pci_physfn(struct pci_dev *dev)
diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index e1e9888..51e9ac0 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -372,6 +372,10 @@
 #define PCI_EA_FIRST_ENT_BRIDGE	8	/* First EA Entry for Bridges */
 #define  PCI_EA_ES		0x00000007 /* Entry Size */
 #define  PCI_EA_BEI		0x000000f0 /* BAR Equivalent Indicator */
+/* Fixed Secondary and Subordinate bus numbers in EA for Bridge */
+#define   PCI_EA_FIXED_SEC_BUS		0xff
+#define   PCI_EA_FIXED_SUB_BUS		0xff00
+#define   PCI_EA_FIXED_SUB_SHIFT	8
 /* 0-5 map to BARs 0-5 respectively */
 #define   PCI_EA_BEI_BAR0		0
 #define   PCI_EA_BEI_BAR5		5
-- 
1.8.3.1