i2c: tegra: Making proper synchronization between isr and caller

Following are the changes:
- Added a mechanism to handle synchronization between caller thread
  and isr so that isr should not get called when clock is disable or
  controller is in reset state.
- Handling tx fifo overflow error.
- Added delay before resetting the controller which is required if
  there is any error in previous transaction so proper stop signal
  will be generated.

Change-Id: I7ac121e056193cd4601f032cdabab59e7e0946ea
Reviewed-on: http://git-master/r/30457
Reviewed-by: Laxman Dewangan <ldewangan@nvidia.com>
Reviewed-by: Alok Chauhan <alokc@nvidia.com>
Tested-by: Alok Chauhan <alokc@nvidia.com>
Tested-by: Laxman Dewangan <ldewangan@nvidia.com>
Reviewed-by: Danielle Sun <dsun@nvidia.com>
Tested-by: Danielle Sun <dsun@nvidia.com>
Reviewed-by: Bo Yan <byan@nvidia.com>
Reviewed-by: Scott Williams <scwilliams@nvidia.com>

1 files changed, 51 insertions, 9 deletions

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 08d0a7f0a8b9..f9a14a75563c 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -31,6 +31,7 @@
 #include <linux/delay.h>
 #include <linux/slab.h>
 #include <linux/i2c-tegra.h>
+#include <linux/spinlock.h>
 
 #include <asm/unaligned.h>
 
@@ -125,10 +126,12 @@ struct tegra_i2c_dev {
 	struct clk *clk;
 	struct resource *iomem;
 	struct rt_mutex dev_lock;
+	spinlock_t clk_lock;
 	void __iomem *base;
 	int cont_id;
 	int irq;
 	bool irq_disabled;
+	bool controller_enabled;
 	int is_dvc;
 	bool is_slave;
 	struct completion msg_complete;
@@ -343,6 +346,10 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
 	if (!i2c_dev->is_clkon_always)
 		clk_enable(i2c_dev->clk);
 
+	/* Interrupt generated before sending stop signal so
+	* wait for some time so that stop signal can be send proerly */
+	udelay(100);
+
 	tegra_periph_reset_assert(i2c_dev->clk);
 	udelay(2);
 	tegra_periph_reset_deassert(i2c_dev->clk);
@@ -379,8 +386,16 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
 static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
 {
 	u32 status;
-	const u32 status_err = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST;
+	const u32 status_err = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST | I2C_INT_TX_FIFO_OVERFLOW;
 	struct tegra_i2c_dev *i2c_dev = dev_id;
+	unsigned long flags;
+
+	spin_lock_irqsave(&i2c_dev->clk_lock, flags);
+	if (!i2c_dev->controller_enabled) {
+		dev_warn(i2c_dev->dev, "Controller not enabled\n");
+		spin_unlock_irqrestore(&i2c_dev->clk_lock, flags);
+		return IRQ_NONE;
+	}
 
 	status = i2c_readl(i2c_dev, I2C_INT_STATUS);
 
@@ -394,7 +409,6 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
 			i2c_dev->irq_disabled = 1;
 		}
 
-		complete(&i2c_dev->msg_complete);
 		goto err;
 	}
 
@@ -416,7 +430,13 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
 				i2c_readl(i2c_dev, I2C_PACKET_TRANSFER_STATUS));
 		}
 
-		complete(&i2c_dev->msg_complete);
+		if (status & I2C_INT_TX_FIFO_OVERFLOW) {
+			i2c_dev->msg_err |= I2C_INT_TX_FIFO_OVERFLOW;
+			dev_warn(i2c_dev->dev, "Tx fifo overflow during "
+				" communicate to add 0x%x\n", i2c_dev->msg_add);
+			dev_warn(i2c_dev->dev, "Packet status 0x%08x\n",
+				i2c_readl(i2c_dev, I2C_PACKET_TRANSFER_STATUS));
+		}
 		goto err;
 	}
 
@@ -432,7 +452,6 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
 			i2c_dev->irq_disabled = 1;
 		}
 
-		complete(&i2c_dev->msg_complete);
 		goto err;
 	}
 
@@ -453,14 +472,15 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
 	if (status & I2C_INT_PACKET_XFER_COMPLETE)
 		i2c_dev->msg_transfer_complete = 1;
 
-	if (i2c_dev->msg_transfer_complete && !i2c_dev->msg_buf_remaining)
-		complete(&i2c_dev->msg_complete);
-
 	i2c_writel(i2c_dev, status, I2C_INT_STATUS);
 
 	if (i2c_dev->is_dvc)
 		dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS);
 
+	if (i2c_dev->msg_transfer_complete && !i2c_dev->msg_buf_remaining)
+		complete(&i2c_dev->msg_complete);
+
+	spin_unlock_irqrestore(&i2c_dev->clk_lock, flags);
 	return IRQ_HANDLED;
 
 err:
@@ -487,13 +507,15 @@ err:
 	/* An error occured, mask all interrupts */
 	tegra_i2c_mask_irq(i2c_dev, I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST |
 		I2C_INT_PACKET_XFER_COMPLETE | I2C_INT_TX_FIFO_DATA_REQ |
-		I2C_INT_RX_FIFO_DATA_REQ);
+		I2C_INT_RX_FIFO_DATA_REQ | I2C_INT_TX_FIFO_OVERFLOW);
 
 	i2c_writel(i2c_dev, status, I2C_INT_STATUS);
 
 	if (i2c_dev->is_dvc)
 		dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS);
 
+	complete(&i2c_dev->msg_complete);
+	spin_unlock_irqrestore(&i2c_dev->clk_lock, flags);
 	return IRQ_HANDLED;
 }
 
@@ -503,6 +525,7 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_bus *i2c_bus,
 	struct tegra_i2c_dev *i2c_dev = i2c_bus->dev;
 	u32 int_mask;
 	int ret;
+	unsigned long flags;
 
 	tegra_i2c_flush_fifos(i2c_dev);
 
@@ -542,7 +565,7 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_bus *i2c_bus,
 	if (!(msg->flags & I2C_M_RD))
 		tegra_i2c_fill_tx_fifo(i2c_dev);
 
-	int_mask = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST;
+	int_mask = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST | I2C_INT_TX_FIFO_OVERFLOW;
 	if (msg->flags & I2C_M_RD)
 		int_mask |= I2C_INT_RX_FIFO_DATA_REQ;
 	else if (i2c_dev->msg_buf_remaining)
@@ -559,7 +582,10 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_bus *i2c_bus,
 			"i2c transfer timed out, addr 0x%04x, data 0x%02x\n",
 			msg->addr, msg->buf[0]);
 
+		spin_lock_irqsave(&i2c_dev->clk_lock, flags);
+		i2c_dev->controller_enabled = false;
 		tegra_i2c_init(i2c_dev);
+		spin_unlock_irqrestore(&i2c_dev->clk_lock, flags);
 		return -ETIMEDOUT;
 	}
 
@@ -569,7 +595,11 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_bus *i2c_bus,
 	if (likely(i2c_dev->msg_err == I2C_ERR_NONE))
 		return 0;
 
+	spin_lock_irqsave(&i2c_dev->clk_lock, flags);
+	i2c_dev->controller_enabled = false;
 	tegra_i2c_init(i2c_dev);
+	spin_unlock_irqrestore(&i2c_dev->clk_lock, flags);
+
 	if (i2c_dev->msg_err == I2C_ERR_NO_ACK) {
 		if (msg->flags & I2C_M_IGNORE_NAK)
 			return 0;
@@ -589,6 +619,7 @@ static int tegra_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 	struct tegra_i2c_dev *i2c_dev = i2c_bus->dev;
 	int i;
 	int ret = 0;
+	unsigned long flags;
 
 	if (i2c_dev->is_suspended)
 		return -EBUSY;
@@ -614,6 +645,11 @@ static int tegra_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 
 	if (!i2c_dev->is_clkon_always)
 		clk_enable(i2c_dev->clk);
+
+	spin_lock_irqsave(&i2c_dev->clk_lock, flags);
+	i2c_dev->controller_enabled = true;
+	spin_unlock_irqrestore(&i2c_dev->clk_lock, flags);
+
 	for (i = 0; i < num; i++) {
 		int stop = (i == (num - 1)) ? 1  : 0;
 		ret = tegra_i2c_xfer_msg(i2c_bus, &msgs[i], stop);
@@ -623,6 +659,10 @@ static int tegra_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 	ret = i;
 
 out:
+	spin_lock_irqsave(&i2c_dev->clk_lock, flags);
+	i2c_dev->controller_enabled = false;
+	spin_unlock_irqrestore(&i2c_dev->clk_lock, flags);
+
 	if (!i2c_dev->is_clkon_always)
 		clk_disable(i2c_dev->clk);
 
@@ -720,7 +760,9 @@ static int tegra_i2c_probe(struct platform_device *pdev)
 	i2c_dev->last_bus_clk = plat->bus_clk_rate[0] ?: 100000;
 	i2c_dev->msgs = NULL;
 	i2c_dev->msgs_num = 0;
+	i2c_dev->controller_enabled = false;
 	rt_mutex_init(&i2c_dev->dev_lock);
+	spin_lock_init(&i2c_dev->clk_lock);
 
 	i2c_dev->slave_addr = plat->slave_addr;
 	i2c_dev->is_dvc = plat->is_dvc;