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Date:   Tue, 5 May 2020 07:51:11 +0200
From:   Alain Volmat <alain.volmat@...com>
To:     <wsa@...nel.org>, <robh+dt@...nel.org>
CC:     <mark.rutland@....com>, <pierre-yves.mordret@...com>,
        <mcoquelin.stm32@...il.com>, <alexandre.torgue@...com>,
        <linux-i2c@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <fabrice.gasnier@...com>,
        <alain.volmat@...com>
Subject: [PATCH 4/4] i2c: stm32f7: Add SMBus-specific protocols support

This patch adds the support for SMBus Host notify and SMBus Alert
extensions protocols

Signed-off-by: Alain Volmat <alain.volmat@...com>
---
 drivers/i2c/busses/Kconfig       |   1 +
 drivers/i2c/busses/i2c-stm32f7.c | 198 +++++++++++++++++++++++++++++--
 2 files changed, 189 insertions(+), 10 deletions(-)

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 2f6e39b41e6c..b82c2f7d7d50 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -1024,6 +1024,7 @@ config I2C_STM32F7
 	tristate "STMicroelectronics STM32F7 I2C support"
 	depends on ARCH_STM32 || COMPILE_TEST
 	select I2C_SLAVE
+	select I2C_SMBUS
 	help
 	  Enable this option to add support for STM32 I2C controller embedded
 	  in STM32F7 SoCs.
diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
index 9c9e10ea9199..6d02ddbc1ab4 100644
--- a/drivers/i2c/busses/i2c-stm32f7.c
+++ b/drivers/i2c/busses/i2c-stm32f7.c
@@ -14,10 +14,12 @@
  * This driver is based on i2c-stm32f4.c
  *
  */
+#include <linux/atomic.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/i2c.h>
+#include <linux/i2c-smbus.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>
@@ -50,6 +52,8 @@
 
 /* STM32F7 I2C control 1 */
 #define STM32F7_I2C_CR1_PECEN			BIT(23)
+#define STM32F7_I2C_CR1_ALERTEN			BIT(22)
+#define STM32F7_I2C_CR1_SMBHEN			BIT(20)
 #define STM32F7_I2C_CR1_WUPEN			BIT(18)
 #define STM32F7_I2C_CR1_SBC			BIT(16)
 #define STM32F7_I2C_CR1_RXDMAEN			BIT(15)
@@ -121,6 +125,7 @@
 				(((n) & STM32F7_I2C_ISR_ADDCODE_MASK) >> 17)
 #define STM32F7_I2C_ISR_DIR			BIT(16)
 #define STM32F7_I2C_ISR_BUSY			BIT(15)
+#define STM32F7_I2C_ISR_ALERT			BIT(13)
 #define STM32F7_I2C_ISR_PECERR			BIT(11)
 #define STM32F7_I2C_ISR_ARLO			BIT(9)
 #define STM32F7_I2C_ISR_BERR			BIT(8)
@@ -134,6 +139,7 @@
 #define STM32F7_I2C_ISR_TXE			BIT(0)
 
 /* STM32F7 I2C Interrupt Clear */
+#define STM32F7_I2C_ICR_ALERTCF			BIT(13)
 #define STM32F7_I2C_ICR_PECCF			BIT(11)
 #define STM32F7_I2C_ICR_ARLOCF			BIT(9)
 #define STM32F7_I2C_ICR_BERRCF			BIT(8)
@@ -150,7 +156,7 @@
 
 #define STM32F7_I2C_MAX_LEN			0xff
 #define STM32F7_I2C_DMA_LEN_MIN			0x16
-#define STM32F7_I2C_MAX_SLAVE			0x2
+#define STM32F7_I2C_MAX_SLAVE			0x3
 
 #define STM32F7_I2C_DNF_DEFAULT			0
 #define STM32F7_I2C_DNF_MAX			16
@@ -274,6 +280,29 @@ struct stm32f7_i2c_msg {
 	u8 smbus_buf[I2C_SMBUS_BLOCK_MAX + 3] __aligned(4);
 };
 
+/**
+ * struct stm32f7_i2c_host - SMBus host specific data
+ * @client: I2C slave device that represents SMBus host
+ * @notify_start: indicate that this is the start of the notify transaction
+ * @addr: device address of SMBus device that initiate SMBus host protocol
+ */
+struct stm32f7_i2c_host {
+	struct i2c_client *client;
+	bool notify_start;
+	u8 addr;
+};
+
+/**
+ * struct stm32f7_i2c_alert - SMBus alert specific data
+ * @setup: platform data for the smbus_alert i2c client
+ * @ara: I2C slave device used to respond to the SMBus Alert with Alert
+ * Response Address
+ */
+struct stm32f7_i2c_alert {
+	struct i2c_smbus_alert_setup setup;
+	struct i2c_client *ara;
+};
+
 /**
  * struct stm32f7_i2c_dev - private data of the controller
  * @adap: I2C adapter for this controller
@@ -301,6 +330,9 @@ struct stm32f7_i2c_msg {
  * @fmp_creg: register address for clearing Fast Mode Plus bits
  * @fmp_mask: mask for Fast Mode Plus bits in set register
  * @wakeup_src: boolean to know if the device is a wakeup source
+ * @host_notify_cnt: atomic to know number of host_notify enabled clients
+ * @host_notify_client: SMBus host-notify client
+ * @alert: SMBus alert specific data
  */
 struct stm32f7_i2c_dev {
 	struct i2c_adapter adap;
@@ -327,6 +359,9 @@ struct stm32f7_i2c_dev {
 	u32 fmp_creg;
 	u32 fmp_mask;
 	bool wakeup_src;
+	atomic_t host_notify_cnt;
+	struct i2c_client *host_notify_client;
+	struct stm32f7_i2c_alert *alert;
 };
 
 /*
@@ -1321,10 +1356,20 @@ static int stm32f7_i2c_get_free_slave_id(struct stm32f7_i2c_dev *i2c_dev,
 	int i;
 
 	/*
-	 * slave[0] supports 7-bit and 10-bit slave address
-	 * slave[1] supports 7-bit slave address only
+	 * slave[0] support only SMBus Host address (0x8)
+	 * slave[1] supports 7-bit and 10-bit slave address
+	 * slave[2] supports 7-bit slave address only
 	 */
-	for (i = STM32F7_I2C_MAX_SLAVE - 1; i >= 0; i--) {
+	if (atomic_read(&i2c_dev->host_notify_cnt)) {
+		if (slave->addr == 0x08) {
+			if (i2c_dev->slave[0])
+				goto fail;
+			*id = 0;
+			return 0;
+		}
+	}
+
+	for (i = STM32F7_I2C_MAX_SLAVE - 1; i > 0; i--) {
 		if (i == 1 && (slave->flags & I2C_CLIENT_TEN))
 			continue;
 		if (!i2c_dev->slave[i]) {
@@ -1333,6 +1378,7 @@ static int stm32f7_i2c_get_free_slave_id(struct stm32f7_i2c_dev *i2c_dev,
 		}
 	}
 
+fail:
 	dev_err(dev, "Slave 0x%x could not be registered\n", slave->addr);
 
 	return -EINVAL;
@@ -1586,6 +1632,13 @@ static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data)
 		f7_msg->result = -EINVAL;
 	}
 
+	if (status & STM32F7_I2C_ISR_ALERT) {
+		dev_dbg(dev, "<%s>: SMBus alert received\n", __func__);
+		writel_relaxed(STM32F7_I2C_ICR_ALERTCF, base + STM32F7_I2C_ICR);
+		i2c_handle_smbus_alert(i2c_dev->alert->ara);
+		return IRQ_HANDLED;
+	}
+
 	if (!i2c_dev->slave_running) {
 		u32 mask;
 		/* Disable interrupts */
@@ -1776,7 +1829,13 @@ static int stm32f7_i2c_reg_slave(struct i2c_client *slave)
 	if (!stm32f7_i2c_is_slave_registered(i2c_dev))
 		stm32f7_i2c_enable_wakeup(i2c_dev, true);
 
-	if (id == 0) {
+	switch (id) {
+	case 0:
+		/* Slave SMBus Host */
+		i2c_dev->slave[id] = slave;
+		break;
+
+	case 1:
 		/* Configure Own Address 1 */
 		oar1 = readl_relaxed(i2c_dev->base + STM32F7_I2C_OAR1);
 		oar1 &= ~STM32F7_I2C_OAR1_MASK;
@@ -1789,7 +1848,9 @@ static int stm32f7_i2c_reg_slave(struct i2c_client *slave)
 		oar1 |= STM32F7_I2C_OAR1_OA1EN;
 		i2c_dev->slave[id] = slave;
 		writel_relaxed(oar1, i2c_dev->base + STM32F7_I2C_OAR1);
-	} else if (id == 1) {
+		break;
+
+	case 2:
 		/* Configure Own Address 2 */
 		oar2 = readl_relaxed(i2c_dev->base + STM32F7_I2C_OAR2);
 		oar2 &= ~STM32F7_I2C_OAR2_MASK;
@@ -1802,7 +1863,10 @@ static int stm32f7_i2c_reg_slave(struct i2c_client *slave)
 		oar2 |= STM32F7_I2C_OAR2_OA2EN;
 		i2c_dev->slave[id] = slave;
 		writel_relaxed(oar2, i2c_dev->base + STM32F7_I2C_OAR2);
-	} else {
+		break;
+
+	default:
+		dev_err(dev, "I2C slave id not supported\n");
 		ret = -ENODEV;
 		goto pm_free;
 	}
@@ -1843,10 +1907,10 @@ static int stm32f7_i2c_unreg_slave(struct i2c_client *slave)
 	if (ret < 0)
 		return ret;
 
-	if (id == 0) {
+	if (id == 1) {
 		mask = STM32F7_I2C_OAR1_OA1EN;
 		stm32f7_i2c_clr_bits(base + STM32F7_I2C_OAR1, mask);
-	} else {
+	} else if (id == 2) {
 		mask = STM32F7_I2C_OAR2_OA2EN;
 		stm32f7_i2c_clr_bits(base + STM32F7_I2C_OAR2, mask);
 	}
@@ -1911,6 +1975,103 @@ static int stm32f7_i2c_setup_fm_plus_bits(struct platform_device *pdev,
 					  &i2c_dev->fmp_mask);
 }
 
+static int stm32f7_i2c_enable_smbus_host(struct stm32f7_i2c_dev *i2c_dev)
+{
+	struct i2c_adapter *adap = &i2c_dev->adap;
+	void __iomem *base = i2c_dev->base;
+	struct i2c_client *client;
+
+	client = i2c_new_smbus_host_notify_device(adap);
+	if (IS_ERR(client))
+		return PTR_ERR(client);
+
+	i2c_dev->host_notify_client = client;
+
+	/* Enable SMBus Host address */
+	stm32f7_i2c_set_bits(base + STM32F7_I2C_CR1, STM32F7_I2C_CR1_SMBHEN);
+
+	return 0;
+}
+
+static void stm32f7_i2c_disable_smbus_host(struct stm32f7_i2c_dev *i2c_dev)
+{
+	void __iomem *base = i2c_dev->base;
+
+	if (i2c_dev->host_notify_client) {
+		/* Disable SMBus Host address */
+		stm32f7_i2c_clr_bits(base + STM32F7_I2C_CR1,
+				     STM32F7_I2C_CR1_SMBHEN);
+		i2c_free_smbus_host_notify_device(i2c_dev->host_notify_client);
+	}
+}
+
+static int stm32f7_i2c_reg_client(struct i2c_client *client)
+{
+	struct stm32f7_i2c_dev *i2c_dev = i2c_get_adapdata(client->adapter);
+	int ret;
+
+	if (client->flags & I2C_CLIENT_HOST_NOTIFY) {
+		/* Only enable on the first device registration */
+		if (atomic_inc_return(&i2c_dev->host_notify_cnt) == 1) {
+			ret = stm32f7_i2c_enable_smbus_host(i2c_dev);
+			if (ret) {
+				dev_err(i2c_dev->dev,
+					"failed to enable SMBus host notify (%d)\n",
+					ret);
+				return ret;
+			}
+		}
+	}
+
+	return 0;
+}
+
+static void stm32f7_i2c_unreg_client(struct i2c_client *client)
+{
+	struct stm32f7_i2c_dev *i2c_dev = i2c_get_adapdata(client->adapter);
+
+	if (client->flags & I2C_CLIENT_HOST_NOTIFY) {
+		if (atomic_dec_return(&i2c_dev->host_notify_cnt) == 0)
+			stm32f7_i2c_disable_smbus_host(i2c_dev);
+	}
+}
+
+static int stm32f7_i2c_enable_smbus_alert(struct stm32f7_i2c_dev *i2c_dev)
+{
+	struct stm32f7_i2c_alert *alert;
+	struct i2c_adapter *adap = &i2c_dev->adap;
+	struct device *dev = i2c_dev->dev;
+	void __iomem *base = i2c_dev->base;
+
+	alert = devm_kzalloc(dev, sizeof(*alert), GFP_KERNEL);
+	if (!alert)
+		return -ENOMEM;
+
+	alert->ara = i2c_new_smbus_alert_device(adap, &alert->setup);
+	if (IS_ERR(alert->ara))
+		return PTR_ERR(alert->ara);
+
+	i2c_dev->alert = alert;
+
+	/* Enable SMBus Alert */
+	stm32f7_i2c_set_bits(base + STM32F7_I2C_CR1, STM32F7_I2C_CR1_ALERTEN);
+
+	return 0;
+}
+
+static void stm32f7_i2c_disable_smbus_alert(struct stm32f7_i2c_dev *i2c_dev)
+{
+	struct stm32f7_i2c_alert *alert = i2c_dev->alert;
+	void __iomem *base = i2c_dev->base;
+
+	if (alert) {
+		/* Disable SMBus Alert */
+		stm32f7_i2c_clr_bits(base + STM32F7_I2C_CR1,
+				     STM32F7_I2C_CR1_ALERTEN);
+		i2c_unregister_device(alert->ara);
+	}
+}
+
 static u32 stm32f7_i2c_func(struct i2c_adapter *adap)
 {
 	return I2C_FUNC_I2C | I2C_FUNC_10BIT_ADDR | I2C_FUNC_SLAVE |
@@ -1918,7 +2079,7 @@ static u32 stm32f7_i2c_func(struct i2c_adapter *adap)
 		I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA |
 		I2C_FUNC_SMBUS_BLOCK_DATA | I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
 		I2C_FUNC_SMBUS_PROC_CALL | I2C_FUNC_SMBUS_PEC |
-		I2C_FUNC_SMBUS_I2C_BLOCK;
+		I2C_FUNC_SMBUS_I2C_BLOCK | I2C_FUNC_SMBUS_HOST_NOTIFY;
 }
 
 static const struct i2c_algorithm stm32f7_i2c_algo = {
@@ -1927,6 +2088,8 @@ static const struct i2c_algorithm stm32f7_i2c_algo = {
 	.functionality = stm32f7_i2c_func,
 	.reg_slave = stm32f7_i2c_reg_slave,
 	.unreg_slave = stm32f7_i2c_unreg_slave,
+	.reg_client = stm32f7_i2c_reg_client,
+	.unreg_client = stm32f7_i2c_unreg_client,
 };
 
 static int stm32f7_i2c_probe(struct platform_device *pdev)
@@ -2088,6 +2251,16 @@ static int stm32f7_i2c_probe(struct platform_device *pdev)
 	if (ret)
 		goto pm_disable;
 
+	if (device_property_read_bool(&pdev->dev, "st,smbus-alert")) {
+		ret = stm32f7_i2c_enable_smbus_alert(i2c_dev);
+		if (ret) {
+			dev_err(i2c_dev->dev,
+				"failed to enable SMBus alert protocol (%d)\n",
+				ret);
+			goto i2c_adapter_remove;
+		}
+	}
+
 	dev_info(i2c_dev->dev, "STM32F7 I2C-%d bus adapter\n", adap->nr);
 
 	pm_runtime_mark_last_busy(i2c_dev->dev);
@@ -2095,6 +2268,9 @@ static int stm32f7_i2c_probe(struct platform_device *pdev)
 
 	return 0;
 
+i2c_adapter_remove:
+	i2c_del_adapter(adap);
+
 pm_disable:
 	pm_runtime_put_noidle(i2c_dev->dev);
 	pm_runtime_disable(i2c_dev->dev);
@@ -2126,6 +2302,8 @@ static int stm32f7_i2c_remove(struct platform_device *pdev)
 {
 	struct stm32f7_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
 
+	stm32f7_i2c_disable_smbus_alert(i2c_dev);
+
 	i2c_del_adapter(&i2c_dev->adap);
 	pm_runtime_get_sync(i2c_dev->dev);
 
-- 
2.17.1

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