Commit 894acb2f authored by David Box's avatar David Box Committed by Wolfram Sang
Browse files

i2c: designware: Add Intel Baytrail PMIC I2C bus support 



This patch implements an I2C bus sharing mechanism between the host and platform
hardware on select Intel BayTrail SoC platforms using the X-Powers AXP288 PMIC.

On these platforms access to the PMIC must be shared with platform hardware. The
hardware unit assumes full control of the I2C bus and the host must request
access through a special semaphore. Hardware control of the bus also makes it
necessary to disable runtime pm to avoid interfering with hardware transactions.

Signed-off-by: default avatarDavid E. Box <david.e.box@linux.intel.com>
Reviewed-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent c0601d28

drivers/i2c/busses/Kconfig

+11 −0
Original line number Diff line number Diff line
@@ -465,6 +465,17 @@ config I2C_DESIGNWARE_PCI 
	  This driver can also be built as a module.  If so, the module

	  will be called i2c-designware-pci.



config I2C_DESIGNWARE_BAYTRAIL

	bool "Intel Baytrail I2C semaphore support"

	depends on I2C_DESIGNWARE_PLATFORM

	select IOSF_MBI

	help

	  This driver enables managed host access to the PMIC I2C bus on select

	  Intel BayTrail platforms using the X-Powers AXP288 PMIC. It allows

	  the host to request uninterrupted access to the PMIC's I2C bus from

	  the platform firmware controlling it. You should say Y if running on

	  a BayTrail system using the AXP288.



config I2C_EFM32

	tristate "EFM32 I2C controller"

	depends on ARCH_EFM32 || COMPILE_TEST

drivers/i2c/busses/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -41,6 +41,7 @@ obj-$(CONFIG_I2C_DAVINCI) += i2c-davinci.o 
obj-$(CONFIG_I2C_DESIGNWARE_CORE)	+= i2c-designware-core.o

obj-$(CONFIG_I2C_DESIGNWARE_PLATFORM)	+= i2c-designware-platform.o

i2c-designware-platform-objs := i2c-designware-platdrv.o

i2c-designware-platform-$(CONFIG_I2C_DESIGNWARE_BAYTRAIL) += i2c-designware-baytrail.o

obj-$(CONFIG_I2C_DESIGNWARE_PCI)	+= i2c-designware-pci.o

i2c-designware-pci-objs := i2c-designware-pcidrv.o

obj-$(CONFIG_I2C_EFM32)		+= i2c-efm32.o

drivers/i2c/busses/i2c-designware-baytrail.c

0 → 100644
+160 −0
Original line number Diff line number Diff line 
/*

 * Intel BayTrail PMIC I2C bus semaphore implementaion

 * Copyright (c) 2014, 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.

 */

#include <linux/module.h>

#include <linux/delay.h>

#include <linux/device.h>

#include <linux/acpi.h>

#include <linux/i2c.h>

#include <linux/interrupt.h>

#include <asm/iosf_mbi.h>

#include "i2c-designware-core.h"



#define SEMAPHORE_TIMEOUT	100

#define PUNIT_SEMAPHORE		0x7



static unsigned long acquired;



static int get_sem(struct device *dev, u32 *sem)

{

	u32 reg_val;

	int ret;



	ret = iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ, PUNIT_SEMAPHORE,

			    &reg_val);

	if (ret) {

		dev_err(dev, "iosf failed to read punit semaphore\n");

		return ret;

	}



	*sem = reg_val & 0x1;



	return 0;

}



static void reset_semaphore(struct device *dev)

{

	u32 data;



	if (iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ,

				PUNIT_SEMAPHORE, &data)) {

		dev_err(dev, "iosf failed to reset punit semaphore during read\n");

		return;

	}



	data = data & 0xfffffffe;

	if (iosf_mbi_write(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_WRITE,

				 PUNIT_SEMAPHORE, data))

		dev_err(dev, "iosf failed to reset punit semaphore during write\n");

}



int baytrail_i2c_acquire(struct dw_i2c_dev *dev)

{

	u32 sem = 0;

	int ret;

	unsigned long start, end;



	if (!dev || !dev->dev)

		return -ENODEV;



	if (!dev->acquire_lock)

		return 0;



	/* host driver writes 0x2 to side band semaphore register */

	ret = iosf_mbi_write(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_WRITE,

				 PUNIT_SEMAPHORE, 0x2);

	if (ret) {

		dev_err(dev->dev, "iosf punit semaphore request failed\n");

		return ret;

	}



	/* host driver waits for bit 0 to be set in semaphore register */

	start = jiffies;

	end = start + msecs_to_jiffies(SEMAPHORE_TIMEOUT);

	while (!time_after(jiffies, end)) {

		ret = get_sem(dev->dev, &sem);

		if (!ret && sem) {

			acquired = jiffies;

			dev_dbg(dev->dev, "punit semaphore acquired after %ums\n",

				jiffies_to_msecs(jiffies - start));

			return 0;

		}



		usleep_range(1000, 2000);

	}



	dev_err(dev->dev, "punit semaphore timed out, resetting\n");

	reset_semaphore(dev->dev);



	ret = iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ,

		PUNIT_SEMAPHORE, &sem);

	if (!ret)

		dev_err(dev->dev, "iosf failed to read punit semaphore\n");

	else

		dev_err(dev->dev, "PUNIT SEM: %d\n", sem);



	WARN_ON(1);



	return -ETIMEDOUT;

}

EXPORT_SYMBOL(baytrail_i2c_acquire);



void baytrail_i2c_release(struct dw_i2c_dev *dev)

{

	if (!dev || !dev->dev)

		return;



	if (!dev->acquire_lock)

		return;



	reset_semaphore(dev->dev);

	dev_dbg(dev->dev, "punit semaphore held for %ums\n",

		jiffies_to_msecs(jiffies - acquired));

}

EXPORT_SYMBOL(baytrail_i2c_release);



int i2c_dw_eval_lock_support(struct dw_i2c_dev *dev)

{

	acpi_status status;

	unsigned long long shared_host = 0;

	acpi_handle handle;



	if (!dev || !dev->dev)

		return 0;



	handle = ACPI_HANDLE(dev->dev);

	if (!handle)

		return 0;



	status = acpi_evaluate_integer(handle, "_SEM", NULL, &shared_host);



	if (ACPI_FAILURE(status))

		return 0;



	if (shared_host) {

		dev_info(dev->dev, "I2C bus managed by PUNIT\n");

		dev->acquire_lock = baytrail_i2c_acquire;

		dev->release_lock = baytrail_i2c_release;

		dev->pm_runtime_disabled = true;

	}



	if (!iosf_mbi_available())

		return -EPROBE_DEFER;



	return 0;

}

EXPORT_SYMBOL(i2c_dw_eval_lock_support);



MODULE_AUTHOR("David E. Box <david.e.box@linux.intel.com>");

MODULE_DESCRIPTION("Baytrail I2C Semaphore driver");

MODULE_LICENSE("GPL v2");

drivers/i2c/busses/i2c-designware-core.h

+6 −0
Original line number Diff line number Diff line
@@ -125,3 +125,9 @@ extern void i2c_dw_disable(struct dw_i2c_dev *dev); 
extern void i2c_dw_clear_int(struct dw_i2c_dev *dev);

extern void i2c_dw_disable_int(struct dw_i2c_dev *dev);

extern u32 i2c_dw_read_comp_param(struct dw_i2c_dev *dev);



#if IS_ENABLED(CONFIG_I2C_DESIGNWARE_BAYTRAIL)

extern int i2c_dw_eval_lock_support(struct dw_i2c_dev *dev);

#else

static inline int i2c_dw_eval_lock_support(struct dw_i2c_dev *dev) { return 0; }

#endif

drivers/i2c/busses/i2c-designware-platdrv.c

+15 −5
Original line number Diff line number Diff line
@@ -195,6 +195,10 @@ static int dw_i2c_probe(struct platform_device *pdev) 
			clk_freq = pdata->i2c_scl_freq;

	}



	r = i2c_dw_eval_lock_support(dev);

	if (r)

		return r;



	dev->functionality =

		I2C_FUNC_I2C |

		I2C_FUNC_10BIT_ADDR |
@@ -257,10 +261,14 @@ static int dw_i2c_probe(struct platform_device *pdev) 
		return r;

	}



	if (dev->pm_runtime_disabled) {

		pm_runtime_forbid(&pdev->dev);

	} else {

		pm_runtime_set_autosuspend_delay(&pdev->dev, 1000);

		pm_runtime_use_autosuspend(&pdev->dev);

		pm_runtime_set_active(&pdev->dev);

		pm_runtime_enable(&pdev->dev);

	}



	return 0;

}
@@ -310,6 +318,8 @@ static int dw_i2c_resume(struct device *dev) 
	struct dw_i2c_dev *i_dev = platform_get_drvdata(pdev);



	clk_prepare_enable(i_dev->clk);



	if (!i_dev->pm_runtime_disabled)

		i2c_dw_init(i_dev);



	return 0;

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