[3.16.y-ckt stable] Patch "iio: adis16400: Fix burst mode" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    iio: adis16400: Fix burst mode

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt14.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From ab7e7fbf26ff348ec6e856ca07235434457363b4 Mon Sep 17 00:00:00 2001
From: Paul Cercueil <paul.cercueil at analog.com>
Date: Fri, 15 May 2015 17:18:37 +0200
Subject: iio: adis16400: Fix burst mode

commit 9df560350c90f3d3909fe653399b3584c9a17b61 upstream.

There are a few issues with the burst mode support. For one we don't setup
the rx buffer, so the buffer will never be filled and all samples will read
as the zero. Furthermore the tx buffer has the wrong type, which means the
driver sends the wrong command and not the right data is returned.

The final issue is that in burst mode all channels are transferred. Hence
the length of the transfer length should be the number of hardware
channels * 2 bytes. Currently the driver uses indio_dev->scan_bytes for
this. But if the timestamp channel is enabled the scan_bytes will be larger
than the burst length. Fix this by just calculating the burst length based
on the number of hardware channels.

Signed-off-by: Paul Cercueil <paul.cercueil at analog.com>
Signed-off-by: Lars-Peter Clausen <lars at metafoo.de>
Fixes: 5eda3550a3cc ("staging:iio:adis16400: Preallocate transfer message")
Signed-off-by: Jonathan Cameron <jic23 at kernel.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/iio/imu/adis16400_buffer.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/iio/imu/adis16400_buffer.c b/drivers/iio/imu/adis16400_buffer.c
index 6e727ffe5262..629ae84d4e62 100644
--- a/drivers/iio/imu/adis16400_buffer.c
+++ b/drivers/iio/imu/adis16400_buffer.c
@@ -18,7 +18,8 @@ int adis16400_update_scan_mode(struct iio_dev *indio_dev,
 {
 	struct adis16400_state *st = iio_priv(indio_dev);
 	struct adis *adis = &st->adis;
-	uint16_t *tx;
+	unsigned int burst_length;
+	u8 *tx;

 	if (st->variant->flags & ADIS16400_NO_BURST)
 		return adis_update_scan_mode(indio_dev, scan_mask);
@@ -26,26 +27,27 @@ int adis16400_update_scan_mode(struct iio_dev *indio_dev,
 	kfree(adis->xfer);
 	kfree(adis->buffer);

+	/* All but the timestamp channel */
+	burst_length = (indio_dev->num_channels - 1) * sizeof(u16);
+
 	adis->xfer = kcalloc(2, sizeof(*adis->xfer), GFP_KERNEL);
 	if (!adis->xfer)
 		return -ENOMEM;

-	adis->buffer = kzalloc(indio_dev->scan_bytes + sizeof(u16),
-		GFP_KERNEL);
+	adis->buffer = kzalloc(burst_length + sizeof(u16), GFP_KERNEL);
 	if (!adis->buffer)
 		return -ENOMEM;

-	tx = adis->buffer + indio_dev->scan_bytes;
-
+	tx = adis->buffer + burst_length;
 	tx[0] = ADIS_READ_REG(ADIS16400_GLOB_CMD);
 	tx[1] = 0;

 	adis->xfer[0].tx_buf = tx;
 	adis->xfer[0].bits_per_word = 8;
 	adis->xfer[0].len = 2;
-	adis->xfer[1].tx_buf = tx;
+	adis->xfer[1].rx_buf = adis->buffer;
 	adis->xfer[1].bits_per_word = 8;
-	adis->xfer[1].len = indio_dev->scan_bytes;
+	adis->xfer[1].len = burst_length;

 	spi_message_init(&adis->msg);
 	spi_message_add_tail(&adis->xfer[0], &adis->msg);