2 files changed, 204 insertions, 33 deletions

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index b3a1f9259b62..fdde7061ef58 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -527,6 +527,10 @@ int spi_register_master(struct spi_master *master)
                 dynamic = 1;
         }
 
+        spin_lock_init(&master->bus_lock_spinlock);
+        mutex_init(&master->bus_lock_mutex);
+        master->bus_lock_flag = 0;
+
         /* register the device, then userspace will see it.
          * registration fails if the bus ID is in use.
          */
@@ -666,6 +670,35 @@ int spi_setup(struct spi_device *spi)
 }
 EXPORT_SYMBOL_GPL(spi_setup);
 
+static int __spi_async(struct spi_device *spi, struct spi_message *message)
+{
+        struct spi_master *master = spi->master;
+
+        /* Half-duplex links include original MicroWire, and ones with
+         * only one data pin like SPI_3WIRE (switches direction) or where
+         * either MOSI or MISO is missing.  They can also be caused by
+         * software limitations.
+         */
+        if ((master->flags & SPI_MASTER_HALF_DUPLEX)
+                        || (spi->mode & SPI_3WIRE)) {
+                struct spi_transfer *xfer;
+                unsigned flags = master->flags;
+
+                list_for_each_entry(xfer, &message->transfers, transfer_list) {
+                        if (xfer->rx_buf && xfer->tx_buf)
+                                return -EINVAL;
+                        if ((flags & SPI_MASTER_NO_TX) && xfer->tx_buf)
+                                return -EINVAL;
+                        if ((flags & SPI_MASTER_NO_RX) && xfer->rx_buf)
+                                return -EINVAL;
+                }
+        }
+
+        message->spi = spi;
+        message->status = -EINPROGRESS;
+        return master->transfer(spi, message);
+}
+
 /**
  * spi_async - asynchronous SPI transfer
  * @spi: device with which data will be exchanged
@@ -698,33 +731,68 @@ EXPORT_SYMBOL_GPL(spi_setup);
 int spi_async(struct spi_device *spi, struct spi_message *message)
 {
         struct spi_master *master = spi->master;
+        int ret;
+        unsigned long flags;
 
-        /* Half-duplex links include original MicroWire, and ones with
-         * only one data pin like SPI_3WIRE (switches direction) or where
-         * either MOSI or MISO is missing.  They can also be caused by
-         * software limitations.
-         */
-        if ((master->flags & SPI_MASTER_HALF_DUPLEX)
-                        || (spi->mode & SPI_3WIRE)) {
-                struct spi_transfer *xfer;
-                unsigned flags = master->flags;
+        spin_lock_irqsave(&master->bus_lock_spinlock, flags);
 
-                list_for_each_entry(xfer, &message->transfers, transfer_list) {
-                        if (xfer->rx_buf && xfer->tx_buf)
-                                return -EINVAL;
-                        if ((flags & SPI_MASTER_NO_TX) && xfer->tx_buf)
-                                return -EINVAL;
-                        if ((flags & SPI_MASTER_NO_RX) && xfer->rx_buf)
-                                return -EINVAL;
-                }
-        }
+        if (master->bus_lock_flag)
+                ret = -EBUSY;
+        else
+                ret = __spi_async(spi, message);
 
-        message->spi = spi;
-        message->status = -EINPROGRESS;
-        return master->transfer(spi, message);
+        spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);
+
+        return ret;
 }
 EXPORT_SYMBOL_GPL(spi_async);
 
+/**
+ * spi_async_locked - version of spi_async with exclusive bus usage
+ * @spi: device with which data will be exchanged
+ * @message: describes the data transfers, including completion callback
+ * Context: any (irqs may be blocked, etc)
+ *
+ * This call may be used in_irq and other contexts which can't sleep,
+ * as well as from task contexts which can sleep.
+ *
+ * The completion callback is invoked in a context which can't sleep.
+ * Before that invocation, the value of message->status is undefined.
+ * When the callback is issued, message->status holds either zero (to
+ * indicate complete success) or a negative error code.  After that
+ * callback returns, the driver which issued the transfer request may
+ * deallocate the associated memory; it's no longer in use by any SPI
+ * core or controller driver code.
+ *
+ * Note that although all messages to a spi_device are handled in
+ * FIFO order, messages may go to different devices in other orders.
+ * Some device might be higher priority, or have various "hard" access
+ * time requirements, for example.
+ *
+ * On detection of any fault during the transfer, processing of
+ * the entire message is aborted, and the device is deselected.
+ * Until returning from the associated message completion callback,
+ * no other spi_message queued to that device will be processed.
+ * (This rule applies equally to all the synchronous transfer calls,
+ * which are wrappers around this core asynchronous primitive.)
+ */
+int spi_async_locked(struct spi_device *spi, struct spi_message *message)
+{
+        struct spi_master *master = spi->master;
+        int ret;
+        unsigned long flags;
+
+        spin_lock_irqsave(&master->bus_lock_spinlock, flags);
+
+        ret = __spi_async(spi, message);
+
+        spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);
+
+        return ret;
+
+}
+EXPORT_SYMBOL_GPL(spi_async_locked);
+
 
 /*-------------------------------------------------------------------------*/
 
@@ -738,6 +806,32 @@ static void spi_complete(void *arg)
         complete(arg);
 }
 
+static int __spi_sync(struct spi_device *spi, struct spi_message *message,
+                      int bus_locked)
+{
+        DECLARE_COMPLETION_ONSTACK(done);
+        int status;
+        struct spi_master *master = spi->master;
+
+        message->complete = spi_complete;
+        message->context = &done;
+
+        if (!bus_locked)
+                mutex_lock(&master->bus_lock_mutex);
+
+        status = spi_async_locked(spi, message);
+
+        if (!bus_locked)
+                mutex_unlock(&master->bus_lock_mutex);
+
+        if (status == 0) {
+                wait_for_completion(&done);
+                status = message->status;
+        }
+        message->context = NULL;
+        return status;
+}
+
 /**
  * spi_sync - blocking/synchronous SPI data transfers
  * @spi: device with which data will be exchanged
@@ -761,21 +855,86 @@ static void spi_complete(void *arg)
  */
 int spi_sync(struct spi_device *spi, struct spi_message *message)
 {
-        DECLARE_COMPLETION_ONSTACK(done);
-        int status;
-
-        message->complete = spi_complete;
-        message->context = &done;
-        status = spi_async(spi, message);
-        if (status == 0) {
-                wait_for_completion(&done);
-                status = message->status;
-        }
-        message->context = NULL;
-        return status;
+        return __spi_sync(spi, message, 0);
 }
 EXPORT_SYMBOL_GPL(spi_sync);
 
+/**
+ * spi_sync_locked - version of spi_sync with exclusive bus usage
+ * @spi: device with which data will be exchanged
+ * @message: describes the data transfers
+ * Context: can sleep
+ *
+ * This call may only be used from a context that may sleep.  The sleep
+ * is non-interruptible, and has no timeout.  Low-overhead controller
+ * drivers may DMA directly into and out of the message buffers.
+ *
+ * This call should be used by drivers that require exclusive access to the
+ * SPI bus. It has to be preceeded by a spi_bus_lock call. The SPI bus must
+ * be released by a spi_bus_unlock call when the exclusive access is over.
+ *
+ * It returns zero on success, else a negative error code.
+ */
+int spi_sync_locked(struct spi_device *spi, struct spi_message *message)
+{
+        return __spi_sync(spi, message, 1);
+}
+EXPORT_SYMBOL_GPL(spi_sync_locked);
+
+/**
+ * spi_bus_lock - obtain a lock for exclusive SPI bus usage
+ * @master: SPI bus master that should be locked for exclusive bus access
+ * Context: can sleep
+ *
+ * This call may only be used from a context that may sleep.  The sleep
+ * is non-interruptible, and has no timeout.
+ *
+ * This call should be used by drivers that require exclusive access to the
+ * SPI bus. The SPI bus must be released by a spi_bus_unlock call when the
+ * exclusive access is over. Data transfer must be done by spi_sync_locked
+ * and spi_async_locked calls when the SPI bus lock is held.
+ *
+ * It returns zero on success, else a negative error code.
+ */
+int spi_bus_lock(struct spi_master *master)
+{
+        unsigned long flags;
+
+        mutex_lock(&master->bus_lock_mutex);
+
+        spin_lock_irqsave(&master->bus_lock_spinlock, flags);
+        master->bus_lock_flag = 1;
+        spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);
+
+        /* mutex remains locked until spi_bus_unlock is called */
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(spi_bus_lock);
+
+/**
+ * spi_bus_unlock - release the lock for exclusive SPI bus usage
+ * @master: SPI bus master that was locked for exclusive bus access
+ * Context: can sleep
+ *
+ * This call may only be used from a context that may sleep.  The sleep
+ * is non-interruptible, and has no timeout.
+ *
+ * This call releases an SPI bus lock previously obtained by an spi_bus_lock
+ * call.
+ *
+ * It returns zero on success, else a negative error code.
+ */
+int spi_bus_unlock(struct spi_master *master)
+{
+        master->bus_lock_flag = 0;
+
+        mutex_unlock(&master->bus_lock_mutex);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(spi_bus_unlock);
+
 /* portable code must never pass more than 32 bytes */
 #define SPI_BUFSIZ      max(32,SMP_CACHE_BYTES)
 
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index af56071b06f9..ae0a5286f558 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -262,6 +262,13 @@ struct spi_master {
 #define SPI_MASTER_NO_RX        BIT(1)          /* can't do buffer read */
 #define SPI_MASTER_NO_TX        BIT(2)          /* can't do buffer write */
 
+        /* lock and mutex for SPI bus locking */
+        spinlock_t              bus_lock_spinlock;
+        struct mutex            bus_lock_mutex;
+
+        /* flag indicating that the SPI bus is locked for exclusive use */
+        bool                    bus_lock_flag;
+
         /* Setup mode and clock, etc (spi driver may call many times).
          *
          * IMPORTANT:  this may be called when transfers to another
@@ -542,6 +549,8 @@ static inline void spi_message_free(struct spi_message *m)
 
 extern int spi_setup(struct spi_device *spi);
 extern int spi_async(struct spi_device *spi, struct spi_message *message);
+extern int spi_async_locked(struct spi_device *spi,
+                            struct spi_message *message);
 
 /*---------------------------------------------------------------------------*/
 
@@ -551,6 +560,9 @@ extern int spi_async(struct spi_device *spi, struct spi_message *message);
  */
 
 extern int spi_sync(struct spi_device *spi, struct spi_message *message);
+extern int spi_sync_locked(struct spi_device *spi, struct spi_message *message);
+extern int spi_bus_lock(struct spi_master *master);
+extern int spi_bus_unlock(struct spi_master *master);
 
 /**
  * spi_write - SPI synchronous write