[V4,2/2] i2c-designware: Add Intel Baytrail PMIC I2C bus support

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 917c358..9a83c46 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -464,6 +464,17 @@  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
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 78d56c5..15b2965 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -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
diff --git a/drivers/i2c/busses/i2c-designware-baytrail.c b/drivers/i2c/busses/i2c-designware-baytrail.c
new file mode 100644
index 0000000..5f1ff4c
--- /dev/null
+++ b/drivers/i2c/busses/i2c-designware-baytrail.c
@@ -0,0 +1,160 @@ 
+/*
+ * 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");
diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
index a472c91..92ceb65 100644
--- a/drivers/i2c/busses/i2c-designware-core.h
+++ b/drivers/i2c/busses/i2c-designware-core.h
@@ -129,3 +129,9 @@  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
diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index a743115..ac32414 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -199,6 +199,10 @@  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 |
@@ -261,10 +265,14 @@  static int dw_i2c_probe(struct platform_device *pdev)
 		return r;
 	}
 
-	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);
+	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;
 }
@@ -314,7 +322,9 @@  static int dw_i2c_resume(struct device *dev)
 	struct dw_i2c_dev *i_dev = platform_get_drvdata(pdev);
 
 	clk_prepare_enable(i_dev->clk);
-	i2c_dw_init(i_dev);
+
+	if (!i_dev->pm_runtime_disabled)
+		i2c_dw_init(i_dev);
 
 	return 0;
 }