Date:	Thu, 19 Dec 2013 23:01:44 -0800
From:	"David E. Box" <david.e.box@...ux.intel.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	mjg59@...f.ucam.org, linux-kernel@...r.kernel.org,
	platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH v5][RESEND] X86 platform: New BayTrail IOSF-SB MBI driver

On Fri, Dec 20, 2013 at 02:59:29AM +0100, Rafael J. Wysocki wrote:
> On Thursday, December 19, 2013 02:37:46 PM David E. Box wrote:
> > From: "David E. Box" <david.e.box@...ux.intel.com>
> > 
> > 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@...ux.intel.com>
> > ---
> > v5: Converted from pnpacpi/mmio driver to pci/config_space driver as
> >     necessitated by firmware change.
> > 
> > v4: Define driver as platform specific to BayTrail as some platforms cannot
> >     enumerate the MBI using ACPI as noted by Bin Gao <bin.gao@...ux.intel.com>
> >     Renamed register macros and API funcitons to platform specific names.
> >     Changed dependency to PNPACPI as sugessted by Rafael Wysocki <rjw@...ysocki.net>
> > 
> > v3: Converted to PNP ACPI driver as sugessted by Rafael Wysocki <rjw@...ysocki.net>
> >     Removed config visibility to user as suggested by Andi Kleen <andi@...stfloor.org>
> > 
> > v2: Made modular since there was no longer a reason not to
> >     Moved to x86 platform as suggested by Mathhew Garrett <mjg59@...f.ucam.org>
> >     Added probe to init to cause driver load to fail if device not detected.
> > 
> >  drivers/platform/x86/Kconfig          |    8 ++
> >  drivers/platform/x86/Makefile         |    1 +
> >  drivers/platform/x86/intel_baytrail.c |  224 +++++++++++++++++++++++++++++++++
> >  drivers/platform/x86/intel_baytrail.h |   90 +++++++++++++
> >  4 files changed, 323 insertions(+)
> >  create mode 100644 drivers/platform/x86/intel_baytrail.c
> >  create mode 100644 drivers/platform/x86/intel_baytrail.h
> > 
> > diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> > index b51a746..b482e22 100644
> > --- a/drivers/platform/x86/Kconfig
> > +++ b/drivers/platform/x86/Kconfig
> > @@ -819,4 +819,12 @@ 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
> > diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
> > index 5dbe193..b3d4cfd 100644
> > --- a/drivers/platform/x86/Makefile
> > +++ b/drivers/platform/x86/Makefile
> > @@ -55,3 +55,4 @@ 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
> > diff --git a/drivers/platform/x86/intel_baytrail.c b/drivers/platform/x86/intel_baytrail.c
> > new file mode 100644
> > index 0000000..f96626b
> > --- /dev/null
> > +++ b/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 */
> 
> Which lock?
>
> > +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;
> 
> Why not to call the label just err?
> 

I like the clarity since there are multiple goto labels

> > +	}
> > +
> > +	result = pci_write_config_dword(mbi_pdev,
> > +					BT_MBI_MCR_OFFSET, mcr);
> 
> Doesn't that fit into 80 chars?
> 

ok

> > +	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);
> 
> If you said "PCI config access failed with %d\n", you wouldn't need the "error:" thing.
> 

ok

> > +	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);
> 
> Is that a good enough reason to crash the kernel?  Maybe WARN_ON() + return error
> would be sufficient?
> 

Ok.

> > +
> > +	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);
> 
> Same comment here.
> 
> > +
> > +	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);
> 
> And here.
> 
> > +
> > +	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@...ux.intel.com>");
> > +MODULE_DESCRIPTION("BayTrail Mailbox Interface accessor");
> > +MODULE_LICENSE("GPL v2");
> > diff --git a/drivers/platform/x86/intel_baytrail.h b/drivers/platform/x86/intel_baytrail.h
> > new file mode 100644
> > index 0000000..8bcc311
> > --- /dev/null
> > +++ b/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 */
> 
> Are the users of the interface supposed to include this file?
>

Only for the macro definitions.

> Rafael

- Dave
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