X86 platform: New BayTrail IOSF-SB MBI driver

Current Intel SOC cores use a MailBox Interface (MBI) to provide access to unit
devices connected to the system fabric. This driver implements access to this
interface on BayTrail platforms. This is a requirement for drivers that need
access to unit registers on the platform (e.g. accessing the PUNIT for power
management features such as RAPL). Serialized access is handled by all exported
routines with spinlocks.

The API includes 3 functions for access to unit registers:

int bt_mbi_read(u8 port, u8 opcode, u32 offset, u32 *mdr)
int bt_mbi_write(u8 port, u8 opcode, u32 offset, u32 mdr)
int bt_mbi_modify(u8 port, u8 opcode, u32 offset, u32 mdr, u32 mask)

port:	indicating the unit being accessed
opcode:	the read or write port specific opcode
offset:	the register offset within the port
mdr:	the register data to be read, written, or modified
mask:	bit locations in mdr to change

Returns nonzero on error

Note: GPU code handles access to the GFX unit. Therefore access to that unit
with this driver is disallowed to avoid conflicts.

Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>

drivers/platform/x86/Kconfig

@@ -808,4 +808,12 @@ config PVPANIC
 	  a paravirtualized device provided by QEMU; it lets a virtual machine
 	  (guest) communicate panic events to the host.
 
+config INTEL_BAYTRAIL_MBI
+	tristate
+	depends on PCI
+	---help---
+	  Needed on Baytrail platforms for access to the IOSF Sideband Mailbox
+	  Interface. This is a requirement for systems that need to configure
+	  the PUNIT for power management features such as RAPL.
+
 endif # X86_PLATFORM_DEVICES

drivers/platform/x86/Makefile

@@ -54,3 +54,4 @@ obj-$(CONFIG_INTEL_RST)		+= intel-rst.o
 obj-$(CONFIG_INTEL_SMARTCONNECT)	+= intel-smartconnect.o
 
 obj-$(CONFIG_PVPANIC)           += pvpanic.o
+obj-$(CONFIG_INTEL_BAYTRAIL_MBI)	+= intel_baytrail.o

drivers/platform/x86/intel_baytrail.c

@@ -0,0 +1,224 @@
+/*
+ * Baytrail IOSF-SB MailBox Interface Driver
+ * Copyright (c) 2013, Intel Corporation.
+ *
+ * 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.
+ *
+ *
+ * The IOSF-SB is a fabric bus available on Atom based SOC's that uses a
+ * mailbox interface (MBI) to communicate with mutiple devices. This
+ * driver implements BayTrail-specific access to this interface.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/spinlock.h>
+#include <linux/pci.h>
+
+#include "intel_baytrail.h"
+
+static DEFINE_SPINLOCK(iosf_mbi_lock);
+
+static inline u32 iosf_mbi_form_mcr(u8 op, u8 port, u8 offset)
+{
+	return (op << 24) | (port << 16) | (offset << 8) | BT_MBI_ENABLE;
+}
+
+static struct pci_dev *mbi_pdev;	/* one mbi device */
+
+/* Hold lock before calling */
+static int iosf_mbi_pci_read_mdr(u32 mcrx, u32 mcr, u32 *mdr)
+{
+	int result;
+
+	if (!mbi_pdev)
+		return -ENODEV;
+
+	if (mcrx) {
+		result = pci_write_config_dword(mbi_pdev,
+						BT_MBI_MCRX_OFFSET, mcrx);
+		if (result < 0)
+			goto iosf_mbi_read_err;
+	}
+
+	result = pci_write_config_dword(mbi_pdev,
+					BT_MBI_MCR_OFFSET, mcr);
+	if (result < 0)
+		goto iosf_mbi_read_err;
+
+	result = pci_read_config_dword(mbi_pdev,
+				       BT_MBI_MDR_OFFSET, mdr);
+	if (result < 0)
+		goto iosf_mbi_read_err;
+
+	return 0;
+
+iosf_mbi_read_err:
+	dev_err(&mbi_pdev->dev, "error: PCI config operation returned %d\n",
+		result);
+	return result;
+}
+
+/* Hold lock before calling */
+static int iosf_mbi_pci_write_mdr(u32 mcrx, u32 mcr, u32 mdr)
+{
+	int result;
+
+	if (!mbi_pdev)
+		return -ENODEV;
+
+	result = pci_write_config_dword(mbi_pdev,
+					BT_MBI_MDR_OFFSET, mdr);
+	if (result < 0)
+		goto iosf_mbi_write_err;
+
+	if (mcrx) {
+		result = pci_write_config_dword(mbi_pdev,
+			 BT_MBI_MCRX_OFFSET, mcrx);
+		if (result < 0)
+			goto iosf_mbi_write_err;
+	}
+
+	result = pci_write_config_dword(mbi_pdev,
+					BT_MBI_MCR_OFFSET, mcr);
+	if (result < 0)
+		goto iosf_mbi_write_err;
+
+	return 0;
+
+iosf_mbi_write_err:
+	dev_err(&mbi_pdev->dev, "error: PCI config operation returned %d\n",
+		result);
+	return result;
+}
+
+int bt_mbi_read(u8 port, u8 opcode, u32 offset, u32 *mdr)
+{
+	u32 mcr, mcrx;
+	unsigned long flags;
+	int ret;
+
+	/*Access to the GFX unit is handled by GPU code */
+	BUG_ON(port == BT_MBI_UNIT_GFX);
+
+	mcr = iosf_mbi_form_mcr(opcode, port, offset & BT_MBI_MASK_LO);
+	mcrx = offset & BT_MBI_MASK_HI;
+
+	spin_lock_irqsave(&iosf_mbi_lock, flags);
+	ret = iosf_mbi_pci_read_mdr(mcrx, mcr, mdr);
+	spin_unlock_irqrestore(&iosf_mbi_lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL(bt_mbi_read);
+
+int bt_mbi_write(u8 port, u8 opcode, u32 offset, u32 mdr)
+{
+	u32 mcr, mcrx;
+	unsigned long flags;
+	int ret;
+
+	/*Access to the GFX unit is handled by GPU code */
+	BUG_ON(port == BT_MBI_UNIT_GFX);
+
+	mcr = iosf_mbi_form_mcr(opcode, port, offset & BT_MBI_MASK_LO);
+	mcrx = offset & BT_MBI_MASK_HI;
+
+	spin_lock_irqsave(&iosf_mbi_lock, flags);
+	ret = iosf_mbi_pci_write_mdr(mcrx, mcr, mdr);
+	spin_unlock_irqrestore(&iosf_mbi_lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL(bt_mbi_write);
+
+int bt_mbi_modify(u8 port, u8 opcode, u32 offset, u32 mdr, u32 mask)
+{
+	u32 mcr, mcrx;
+	u32 value;
+	unsigned long flags;
+	int ret;
+
+	/*Access to the GFX unit is handled by GPU code */
+	BUG_ON(port == BT_MBI_UNIT_GFX);
+
+	mcr = iosf_mbi_form_mcr(opcode, port, offset & BT_MBI_MASK_LO);
+	mcrx = offset & BT_MBI_MASK_HI;
+
+	spin_lock_irqsave(&iosf_mbi_lock, flags);
+
+	/* Read current mdr value */
+	ret = iosf_mbi_pci_read_mdr(mcrx, mcr & BT_MBI_RD_MASK, &value);
+	if (ret < 0) {
+		spin_unlock_irqrestore(&iosf_mbi_lock, flags);
+		return ret;
+	}
+
+	/* Apply mask */
+	value &= ~mask;
+	mdr &= mask;
+	value |= mdr;
+
+	/* Write back */
+	ret = iosf_mbi_pci_write_mdr(mcrx, mcr | BT_MBI_WR_MASK, value);
+
+	spin_unlock_irqrestore(&iosf_mbi_lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL(bt_mbi_modify);
+
+static int iosf_mbi_probe(struct pci_dev *pdev,
+			  const struct pci_device_id *unused)
+{
+	int ret;
+
+	ret = pci_enable_device(pdev);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "error: could not enable device\n");
+		return ret;
+	}
+
+	mbi_pdev = pci_dev_get(pdev);
+	return 0;
+}
+
+static DEFINE_PCI_DEVICE_TABLE(iosf_mbi_pci_ids) = {
+	{ PCI_DEVICE(PCI_VENDOR_ID_INTEL, 0x0F00) },
+	{ 0, },
+};
+MODULE_DEVICE_TABLE(pci, iosf_mbi_pci_ids);
+
+static struct pci_driver iosf_mbi_pci_driver = {
+	.name		= "iosf_mbi_pci",
+	.probe		= iosf_mbi_probe,
+	.id_table	= iosf_mbi_pci_ids,
+};
+
+static int __init bt_mbi_init(void)
+{
+	return pci_register_driver(&iosf_mbi_pci_driver);
+}
+
+static void __exit bt_mbi_exit(void)
+{
+	pci_unregister_driver(&iosf_mbi_pci_driver);
+	if (mbi_pdev) {
+		pci_dev_put(mbi_pdev);
+		mbi_pdev = NULL;
+	}
+}
+
+module_init(bt_mbi_init);
+module_exit(bt_mbi_exit);
+
+MODULE_AUTHOR("David E. Box <david.e.box@linux.intel.com>");
+MODULE_DESCRIPTION("BayTrail Mailbox Interface accessor");
+MODULE_LICENSE("GPL v2");

drivers/platform/x86/intel_baytrail.h

@@ -0,0 +1,90 @@
+/*
+ * intel_baytrail.h: MailBox access support for Intel BayTrail platforms
+ */
+
+#ifndef INTEL_BAYTRAIL_MBI_SYMS_H
+#define INTEL_BAYTRAIL_MBI_SYMS_H
+
+#define BT_MBI_MCR_OFFSET	0xD0
+#define BT_MBI_MDR_OFFSET	0xD4
+#define BT_MBI_MCRX_OFFSET	0xD8
+
+#define BT_MBI_RD_MASK		0xFEFFFFFF
+#define BT_MBI_WR_MASK		0X01000000
+
+#define BT_MBI_MASK_HI		0xFFFFFF00
+#define BT_MBI_MASK_LO		0x000000FF
+#define BT_MBI_ENABLE		0xF0
+
+/* BT-SB unit access methods */
+#define BT_MBI_UNIT_AUNIT	0x00
+#define BT_MBI_UNIT_SMC		0x01
+#define BT_MBI_UNIT_CPU		0x02
+#define BT_MBI_UNIT_BUNIT	0x03
+#define BT_MBI_UNIT_PMC		0x04
+#define BT_MBI_UNIT_GFX		0x06
+#define BT_MBI_UNIT_SMI		0x0C
+#define BT_MBI_UNIT_USB		0x43
+#define BT_MBI_UNIT_SATA	0xA3
+#define BT_MBI_UNIT_PCIE	0xA6
+
+/* Read/write opcodes */
+#define BT_MBI_AUNIT_READ	0x10
+#define BT_MBI_AUNIT_WRITE	0x11
+#define BT_MBI_SMC_READ		0x10
+#define BT_MBI_SMC_WRITE	0x11
+#define BT_MBI_CPU_READ		0x10
+#define BT_MBI_CPU_WRITE	0x11
+#define BT_MBI_BUNIT_READ	0x10
+#define BT_MBI_BUNIT_WRITE	0x11
+#define BT_MBI_PMC_READ		0x06
+#define BT_MBI_PMC_WRITE	0x07
+#define BT_MBI_GFX_READ		0x00
+#define BT_MBI_GFX_WRITE	0x01
+#define BT_MBI_SMIO_READ	0x06
+#define BT_MBI_SMIO_WRITE	0x07
+#define BT_MBI_USB_READ		0x06
+#define BT_MBI_USB_WRITE	0x07
+#define BT_MBI_SATA_READ	0x00
+#define BT_MBI_SATA_WRITE	0x01
+#define BT_MBI_PCIE_READ	0x00
+#define BT_MBI_PCIE_WRITE	0x01
+
+/**
+ * bt_mbi_read() - MailBox Interface read command
+ * @port:	port indicating subunit being accessed
+ * @opcode:	port specific read or write opcode
+ * @offset:	register address offset
+ * @mdr:	register data to be read
+ *
+ * Locking is handled by spinlock - cannot sleep.
+ * Return: Nonzero on error
+ */
+int bt_mbi_read(u8 port, u8 opcode, u32 offset, u32 *mdr);
+
+/**
+ * bt_mbi_write() - MailBox unmasked write command
+ * @port:	port indicating subunit being accessed
+ * @opcode:	port specific read or write opcode
+ * @offset:	register address offset
+ * @mdr:	register data to be written
+ *
+ * Locking is handled by spinlock - cannot sleep.
+ * Return: Nonzero on error
+ */
+int bt_mbi_write(u8 port, u8 opcode, u32 offset, u32 mdr);
+
+/**
+ * bt_mbi_modify() - MailBox masked write command
+ * @port:	port indicating subunit being accessed
+ * @opcode:	port specific read or write opcode
+ * @offset:	register address offset
+ * @mdr:	register data being modified
+ * @mask:	mask indicating bits in mdr to be modified
+ *
+ * Locking is handled by spinlock - cannot sleep.
+ * Return: Nonzero on error
+ */
+int bt_mbi_modify(u8 port, u8 opcode, u32 offset, u32 mdr, u32 mask);
+
+#endif /* INTEL_BAYTRAIL_MBI_SYMS_H */