1 files changed, 101 insertions, 59 deletions

diff --git a/drivers/staging/axis-fifo/axis-fifo.c b/drivers/staging/axis-fifo/axis-fifo.c
index 39e6c59df1e9..5801067e7c1b 100644
--- a/drivers/staging/axis-fifo/axis-fifo.c
+++ b/drivers/staging/axis-fifo/axis-fifo.c
@@ -16,7 +16,7 @@
 
 #include <linux/kernel.h>
 #include <linux/wait.h>
-#include <linux/spinlock_types.h>
+#include <linux/mutex.h>
 #include <linux/device.h>
 #include <linux/cdev.h>
 #include <linux/init.h>
@@ -133,9 +133,9 @@ struct axis_fifo {
 	int has_tx_fifo; /* whether the IP has the tx fifo enabled */
 
 	wait_queue_head_t read_queue; /* wait queue for asynchronos read */
-	spinlock_t read_queue_lock; /* lock for reading waitqueue */
+	struct mutex read_lock; /* lock for reading */
 	wait_queue_head_t write_queue; /* wait queue for asynchronos write */
-	spinlock_t write_queue_lock; /* lock for writing waitqueue */
+	struct mutex write_lock; /* lock for writing */
 	unsigned int write_flags; /* write file flags */
 	unsigned int read_flags; /* read file flags */
 
@@ -336,7 +336,21 @@ static void reset_ip_core(struct axis_fifo *fifo)
 	iowrite32(XLLF_INT_ALL_MASK, fifo->base_addr + XLLF_ISR_OFFSET);
 }
 
-/* reads a single packet from the fifo as dictated by the tlast signal */
+/**
+ * axis_fifo_write() - Read a packet from AXIS-FIFO character device.
+ * @f Open file.
+ * @buf User space buffer to read to.
+ * @len User space buffer length.
+ * @off Buffer offset.
+ *
+ * As defined by the device's documentation, we need to check the device's
+ * occupancy before reading the length register and then the data. All these
+ * operations must be executed atomically, in order and one after the other
+ * without missing any.
+ *
+ * Returns the number of bytes read from the device or negative error code
+ *	on failure.
+ */
 static ssize_t axis_fifo_read(struct file *f, char __user *buf,
 			      size_t len, loff_t *off)
 {
@@ -350,36 +364,37 @@ static ssize_t axis_fifo_read(struct file *f, char __user *buf,
 	u32 tmp_buf[READ_BUF_SIZE];
 
 	if (fifo->read_flags & O_NONBLOCK) {
-		/* opened in non-blocking mode
-		 * return if there are no packets available
+		/*
+		 * Device opened in non-blocking mode. Try to lock it and then
+		 * check if any packet is available.
 		 */
-		if (!ioread32(fifo->base_addr + XLLF_RDFO_OFFSET))
+		if (!mutex_trylock(&fifo->read_lock))
 			return -EAGAIN;
+
+		if (!ioread32(fifo->base_addr + XLLF_RDFO_OFFSET)) {
+			ret = -EAGAIN;
+			goto end_unlock;
+		}
 	} else {
 		/* opened in blocking mode
 		 * wait for a packet available interrupt (or timeout)
 		 * if nothing is currently available
 		 */
-		spin_lock_irq(&fifo->read_queue_lock);
-		ret = wait_event_interruptible_lock_irq_timeout
-			(fifo->read_queue,
-			 ioread32(fifo->base_addr + XLLF_RDFO_OFFSET),
-			 fifo->read_queue_lock,
-			 (read_timeout >= 0) ? msecs_to_jiffies(read_timeout) :
+		mutex_lock(&fifo->read_lock);
+		ret = wait_event_interruptible_timeout(fifo->read_queue,
+			ioread32(fifo->base_addr + XLLF_RDFO_OFFSET),
+			(read_timeout >= 0) ? msecs_to_jiffies(read_timeout) :
 				MAX_SCHEDULE_TIMEOUT);
-		spin_unlock_irq(&fifo->read_queue_lock);
 
-		if (ret == 0) {
-			/* timeout occurred */
-			dev_dbg(fifo->dt_device, "read timeout");
-			return -EAGAIN;
-		} else if (ret == -ERESTARTSYS) {
-			/* signal received */
-			return -ERESTARTSYS;
-		} else if (ret < 0) {
-			dev_err(fifo->dt_device, "wait_event_interruptible_timeout() error in read (ret=%i)\n",
-				ret);
-			return ret;
+		if (ret <= 0) {
+			if (ret == 0) {
+				ret = -EAGAIN;
+			} else if (ret != -ERESTARTSYS) {
+				dev_err(fifo->dt_device, "wait_event_interruptible_timeout() error in read (ret=%i)\n",
+					ret);
+			}
+
+			goto end_unlock;
 		}
 	}
 
@@ -387,14 +402,16 @@ static ssize_t axis_fifo_read(struct file *f, char __user *buf,
 	if (!bytes_available) {
 		dev_err(fifo->dt_device, "received a packet of length 0 - fifo core will be reset\n");
 		reset_ip_core(fifo);
-		return -EIO;
+		ret = -EIO;
+		goto end_unlock;
 	}
 
 	if (bytes_available > len) {
 		dev_err(fifo->dt_device, "user read buffer too small (available bytes=%zu user buffer bytes=%zu) - fifo core will be reset\n",
 			bytes_available, len);
 		reset_ip_core(fifo);
-		return -EINVAL;
+		ret = -EINVAL;
+		goto end_unlock;
 	}
 
 	if (bytes_available % sizeof(u32)) {
@@ -403,7 +420,8 @@ static ssize_t axis_fifo_read(struct file *f, char __user *buf,
 		 */
 		dev_err(fifo->dt_device, "received a packet that isn't word-aligned - fifo core will be reset\n");
 		reset_ip_core(fifo);
-		return -EIO;
+		ret = -EIO;
+		goto end_unlock;
 	}
 
 	words_available = bytes_available / sizeof(u32);
@@ -423,16 +441,37 @@ static ssize_t axis_fifo_read(struct file *f, char __user *buf,
 		if (copy_to_user(buf + copied * sizeof(u32), tmp_buf,
 				 copy * sizeof(u32))) {
 			reset_ip_core(fifo);
-			return -EFAULT;
+			ret = -EFAULT;
+			goto end_unlock;
 		}
 
 		copied += copy;
 		words_available -= copy;
 	}
 
-	return bytes_available;
+	ret = bytes_available;
+
+end_unlock:
+	mutex_unlock(&fifo->read_lock);
+
+	return ret;
 }
 
+/**
+ * axis_fifo_write() - Write buffer to AXIS-FIFO character device.
+ * @f Open file.
+ * @buf User space buffer to write to the device.
+ * @len User space buffer length.
+ * @off Buffer offset.
+ *
+ * As defined by the device's documentation, we need to write to the device's
+ * data buffer then to the device's packet length register atomically. Also,
+ * we need to lock before checking if the device has available space to avoid
+ * any concurrency issue.
+ *
+ * Returns the number of bytes written to the device or negative error code
+ *	on failure.
+ */
 static ssize_t axis_fifo_write(struct file *f, const char __user *buf,
 			       size_t len, loff_t *off)
 {
@@ -465,12 +504,17 @@ static ssize_t axis_fifo_write(struct file *f, const char __user *buf,
 	}
 
 	if (fifo->write_flags & O_NONBLOCK) {
-		/* opened in non-blocking mode
-		 * return if there is not enough room available in the fifo
+		/*
+		 * Device opened in non-blocking mode. Try to lock it and then
+		 * check if there is any room to write the given buffer.
 		 */
+		if (!mutex_trylock(&fifo->write_lock))
+			return -EAGAIN;
+
 		if (words_to_write > ioread32(fifo->base_addr +
 					      XLLF_TDFV_OFFSET)) {
-			return -EAGAIN;
+			ret = -EAGAIN;
+			goto end_unlock;
 		}
 	} else {
 		/* opened in blocking mode */
@@ -478,30 +522,22 @@ static ssize_t axis_fifo_write(struct file *f, const char __user *buf,
 		/* wait for an interrupt (or timeout) if there isn't
 		 * currently enough room in the fifo
 		 */
-		spin_lock_irq(&fifo->write_queue_lock);
-		ret = wait_event_interruptible_lock_irq_timeout
-			(fifo->write_queue,
-			 ioread32(fifo->base_addr + XLLF_TDFV_OFFSET)
+		mutex_lock(&fifo->write_lock);
+		ret = wait_event_interruptible_timeout(fifo->write_queue,
+			ioread32(fifo->base_addr + XLLF_TDFV_OFFSET)
 				>= words_to_write,
-			 fifo->write_queue_lock,
-			 (write_timeout >= 0) ?
-				msecs_to_jiffies(write_timeout) :
+			(write_timeout >= 0) ? msecs_to_jiffies(write_timeout) :
 				MAX_SCHEDULE_TIMEOUT);
-		spin_unlock_irq(&fifo->write_queue_lock);
 
-		if (ret == 0) {
-			/* timeout occurred */
-			dev_dbg(fifo->dt_device, "write timeout\n");
-			return -EAGAIN;
-		} else if (ret == -ERESTARTSYS) {
-			/* signal received */
-			return -ERESTARTSYS;
-		} else if (ret < 0) {
-			/* unknown error */
-			dev_err(fifo->dt_device,
-				"wait_event_interruptible_timeout() error in write (ret=%i)\n",
-				ret);
-			return ret;
+		if (ret <= 0) {
+			if (ret == 0) {
+				ret = -EAGAIN;
+			} else if (ret != -ERESTARTSYS) {
+				dev_err(fifo->dt_device, "wait_event_interruptible_timeout() error in write (ret=%i)\n",
+					ret);
+			}
+
+			goto end_unlock;
 		}
 	}
 
@@ -515,7 +551,8 @@ static ssize_t axis_fifo_write(struct file *f, const char __user *buf,
 		if (copy_from_user(tmp_buf, buf + copied * sizeof(u32),
 				   copy * sizeof(u32))) {
 			reset_ip_core(fifo);
-			return -EFAULT;
+			ret = -EFAULT;
+			goto end_unlock;
 		}
 
 		for (i = 0; i < copy; i++)
@@ -526,10 +563,15 @@ static ssize_t axis_fifo_write(struct file *f, const char __user *buf,
 		words_to_write -= copy;
 	}
 
+	ret = copied * sizeof(u32);
+
 	/* write packet size to fifo */
-	iowrite32(copied * sizeof(u32), fifo->base_addr + XLLF_TLR_OFFSET);
+	iowrite32(ret, fifo->base_addr + XLLF_TLR_OFFSET);
+
+end_unlock:
+	mutex_unlock(&fifo->write_lock);
 
-	return (ssize_t)copied * sizeof(u32);
+	return ret;
 }
 
 static irqreturn_t axis_fifo_irq(int irq, void *dw)
@@ -789,8 +831,8 @@ static int axis_fifo_probe(struct platform_device *pdev)
 	init_waitqueue_head(&fifo->read_queue);
 	init_waitqueue_head(&fifo->write_queue);
 
-	spin_lock_init(&fifo->read_queue_lock);
-	spin_lock_init(&fifo->write_queue_lock);
+	mutex_init(&fifo->read_lock);
+	mutex_init(&fifo->write_lock);
 
 	/* ----------------------------
 	 *   init device memory space