[PATCH] SPI: spi_bitbang: clocking fixes

This fixes two problems triggered by the MMC stack updating clocks:

 - SPI masters driver should accept a max clock speed of zero; that's one
   convention for marking idle devices.  (Presumably that helps controllers
   that don't autogate clocks to "off" when not in use.)

 - There are more than 1000 nanoseconds per millisecond; setting the clock
   down to 125 KHz now works properly.

Showing once again that Zero (http://en.wikipedia.org/wiki/Zero) is still
an inexhaustible number of bugs.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/spi/spi_bitbang.c

@@ -167,9 +167,11 @@ int spi_bitbang_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
 	/* nsecs = (clock period)/2 */
 	if (!hz)
 		hz = spi->max_speed_hz;
-	cs->nsecs = (1000000000/2) / hz;
-	if (cs->nsecs > MAX_UDELAY_MS * 1000)
-		return -EINVAL;
+	if (hz) {
+		cs->nsecs = (1000000000/2) / hz;
+		if (cs->nsecs > (MAX_UDELAY_MS * 1000 * 1000))
+			return -EINVAL;
+	}
 
 	return 0;
 }
@@ -184,9 +186,6 @@ int spi_bitbang_setup(struct spi_device *spi)
 	struct spi_bitbang	*bitbang;
 	int			retval;
 
-	if (!spi->max_speed_hz)
-		return -EINVAL;
-
 	bitbang = spi_master_get_devdata(spi->master);
 
 	/* REVISIT: some systems will want to support devices using lsb-first
@@ -216,7 +215,7 @@ int spi_bitbang_setup(struct spi_device *spi)
 	if (retval < 0)
 		return retval;
 
-	dev_dbg(&spi->dev, "%s, mode %d, %u bits/w, %u nsec\n",
+	dev_dbg(&spi->dev, "%s, mode %d, %u bits/w, %u nsec/bit\n",
 			__FUNCTION__, spi->mode & (SPI_CPOL | SPI_CPHA),
 			spi->bits_per_word, 2 * cs->nsecs);
 
@@ -405,6 +404,7 @@ int spi_bitbang_transfer(struct spi_device *spi, struct spi_message *m)
 {
 	struct spi_bitbang	*bitbang;
 	unsigned long		flags;
+	int			status = 0;
 
 	m->actual_length = 0;
 	m->status = -EINPROGRESS;
@@ -414,11 +414,15 @@ int spi_bitbang_transfer(struct spi_device *spi, struct spi_message *m)
 		return -ESHUTDOWN;
 
 	spin_lock_irqsave(&bitbang->lock, flags);
-	list_add_tail(&m->queue, &bitbang->queue);
-	queue_work(bitbang->workqueue, &bitbang->work);
+	if (!spi->max_speed_hz)
+		status = -ENETDOWN;
+	else {
+		list_add_tail(&m->queue, &bitbang->queue);
+		queue_work(bitbang->workqueue, &bitbang->work);
+	}
 	spin_unlock_irqrestore(&bitbang->lock, flags);
 
-	return 0;
+	return status;
 }
 EXPORT_SYMBOL_GPL(spi_bitbang_transfer);