[PATCH v2 2/3] x86/platform/p2sb: New Primary to Sideband bridge support driver for Intel SOC's

[Tan Jui Nee]

From: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>

There is already one and at least one more user coming which
require an access to Primary to Sideband bridge (P2SB) in order
to get IO or MMIO bar hidden by BIOS.
Create a driver to access P2SB for x86 devices.

Signed-off-by: Yong, Jonathan <jonathan.yong@xxxxxxxxx>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
 arch/x86/Kconfig                 | 14 ++++++
 arch/x86/include/asm/p2sb.h      | 27 +++++++++++
 arch/x86/platform/intel/Makefile |  1 +
 arch/x86/platform/intel/p2sb.c   | 99 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 141 insertions(+)
 create mode 100644 arch/x86/include/asm/p2sb.h
 create mode 100644 arch/x86/platform/intel/p2sb.c

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2dc18605..589045e 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -606,6 +606,20 @@ config IOSF_MBI_DEBUG
 
 	  If you don't require the option or are in doubt, say N.
 
+config X86_INTEL_NON_ACPI
+	bool "Enable support non-ACPI Intel platforms"
+	select PINCTRL
+	---help---
+	  Select this option to enables MMIO BAR access over the P2SB for
+	  non-ACPI Intel SoC platforms. This driver uses the P2SB hide/unhide
+	  mechanism cooperatively to pass the PCI BAR address to the platform
+	  driver, currently GPIO on the following SoC products.
+	   - Apollo Lake
+
+config P2SB
+	tristate
+	depends on PCI
+
 config X86_RDC321X
 	bool "RDC R-321x SoC"
 	depends on X86_32
diff --git a/arch/x86/include/asm/p2sb.h b/arch/x86/include/asm/p2sb.h
new file mode 100644
index 0000000..686e07b
--- /dev/null
+++ b/arch/x86/include/asm/p2sb.h
@@ -0,0 +1,27 @@
+/*
+ * Primary to Sideband bridge (P2SB) access support
+ */
+
+#ifndef P2SB_SYMS_H
+#define P2SB_SYMS_H
+
+#include <linux/ioport.h>
+#include <linux/pci.h>
+
+#if IS_ENABLED(CONFIG_P2SB)
+
+int p2sb_bar(struct pci_dev *pdev, unsigned int devfn,
+	struct resource *res);
+
+#else /* CONFIG_P2SB is not set */
+
+static inline
+int p2sb_bar(struct pci_dev *pdev, unsigned int devfn,
+	struct resource *res)
+{
+	return -ENODEV;
+}
+
+#endif /* CONFIG_P2SB */
+
+#endif /* P2SB_SYMS_H */
diff --git a/arch/x86/platform/intel/Makefile b/arch/x86/platform/intel/Makefile
index b878032..dbf9f10 100644
--- a/arch/x86/platform/intel/Makefile
+++ b/arch/x86/platform/intel/Makefile
@@ -1 +1,2 @@
 obj-$(CONFIG_IOSF_MBI)			+= iosf_mbi.o
+obj-$(CONFIG_P2SB)			+= p2sb.o
diff --git a/arch/x86/platform/intel/p2sb.c b/arch/x86/platform/intel/p2sb.c
new file mode 100644
index 0000000..8be47a4
--- /dev/null
+++ b/arch/x86/platform/intel/p2sb.c
@@ -0,0 +1,99 @@
+/*
+ * Primary to Sideband bridge (P2SB) driver
+ *
+ * Copyright (c) 2016, Intel Corporation.
+ *
+ * Authors: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
+ *			Jonathan Yong <jonathan.yong@xxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ */
+
+#include <linux/ioport.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/spinlock.h>
+
+#include <asm/p2sb.h>
+
+#define SBREG_BAR	0x10
+#define SBREG_HIDE	0xe1
+
+static DEFINE_SPINLOCK(p2sb_spinlock);
+
+/*
+ * p2sb_bar - Get Primary to Sideband bridge (P2SB) BAR
+ * @pdev:	PCI device to get PCI bus to communicate with
+ * @devfn:	PCI device and function to communicate with
+ * @res:	resources to be filled in
+ *
+ * The BIOS prevents the P2SB device from being enumerated by the PCI
+ * subsystem, so we need to unhide and hide it back to lookup the P2SB BAR.
+ *
+ * Locking is handled by spinlock - cannot sleep.
+ *
+ * Return:
+ * 0 on success or appropriate errno value on error.
+ */
+int p2sb_bar(struct pci_dev *pdev, unsigned int devfn,
+	struct resource *res)
+{
+	u32 base_addr;
+	u64 base64_addr;
+	unsigned long flags;
+
+	if (!res)
+		return -EINVAL;
+
+	spin_lock(&p2sb_spinlock);
+
+	/* Unhide the P2SB device */
+	pci_bus_write_config_byte(pdev->bus, devfn, SBREG_HIDE, 0x00);
+
+	/* Check if device present */
+	pci_bus_read_config_dword(pdev->bus, devfn, 0, &base_addr);
+	if (base_addr == 0xffffffff || base_addr == 0x00000000) {
+		spin_unlock(&p2sb_spinlock);
+		dev_warn(&pdev->dev, "P2SB device access disabled by BIOS?\n");
+		return -ENODEV;
+	}
+
+	/* Get IO or MMIO BAR */
+	pci_bus_read_config_dword(pdev->bus, devfn, SBREG_BAR, &base_addr);
+	if ((base_addr & PCI_BASE_ADDRESS_SPACE) == PCI_BASE_ADDRESS_SPACE_IO) {
+		flags = IORESOURCE_IO;
+		base64_addr = base_addr & PCI_BASE_ADDRESS_IO_MASK;
+	} else {
+		flags = IORESOURCE_MEM;
+		base64_addr = base_addr & PCI_BASE_ADDRESS_MEM_MASK;
+		if (base_addr & PCI_BASE_ADDRESS_MEM_TYPE_64) {
+			flags |= IORESOURCE_MEM_64;
+			pci_bus_read_config_dword(pdev->bus, devfn,
+				SBREG_BAR + 4, &base_addr);
+			base64_addr |= (u64)base_addr << 32;
+		}
+	}
+
+	/* Hide the P2SB device */
+	pci_bus_write_config_byte(pdev->bus, devfn, SBREG_HIDE, 0x01);
+
+	spin_unlock(&p2sb_spinlock);
+
+	/* User provides prefilled resources */
+	res->start += (resource_size_t)base64_addr;
+	res->end += (resource_size_t)base64_addr;
+	res->flags = flags;
+
+	return 0;
+}
+EXPORT_SYMBOL(p2sb_bar);
+
+MODULE_LICENSE("GPL");
-- 
1.9.1