Patch "Input: ads7846 - correct the value got from SPI" has been added to the 3.14-stable tree

This is a note to let you know that I've just added the patch titled

Input: ads7846 - correct the value got from SPI

to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
input-ads7846-correct-the-value-got-from-spi.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Andrey Gelman <[email protected]>
Date: Tue, 6 Oct 2015 15:43:43 -0700
Subject: Input: ads7846 - correct the value got from SPI

From: Andrey Gelman <[email protected]>

commit 879f2fea8a5a748bcbf98d2cdce9139c045505d3 upstream.

According to the touch controller spec, SPI return a 16 bit value, only 12 bits are valid, they are bit[14-3].

The value of MISO and MOSI can be configured when SPI is in idle mode. Currently this touch driver assumes the SPI bus sets the MOSI and MISO in low level when SPI bus is in idle mode. So the bit[15] of the value got from SPI bus is always 0. But when SPI bus congfigures the MOSI and MISO in high level during the SPI idle mode, the bit[15] of the value get from SPI is always 1. If bit[15] is not masked, we may get the wrong value.

Mask the invalid bit to make sure the correct value gets returned. Regardless of the SPI bus idle configuration.

---
 drivers/input/touchscreen/ads7846.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

@@ -668,18 +668,22 @@ static int ads7846_no_filter(void *ads,
 
 static int ads7846_get_value(struct ads7846 *ts, struct spi_message *m)
 {
+	int value;
 	struct spi_transfer *t =
 		list_entry(m->transfers.prev, struct spi_transfer, transfer_list);
 
 	if (ts->model == 7845) {
-		return be16_to_cpup((__be16 *)&(((char*)t->rx_buf)[1])) >> 3;
+		value = be16_to_cpup((__be16 *)&(((char *)t->rx_buf)[1]));
 	} else {
 		/*
 		 * adjust:  on-wire is a must-ignore bit, a BE12 value, then
 		 * padding; built from two 8 bit values written msb-first.
 		 */
-		return be16_to_cpup((__be16 *)t->rx_buf) >> 3;
+		value = be16_to_cpup((__be16 *)t->rx_buf);
 	}
+
+	/* enforce ADC output is 12 bits width */
+	return (value >> 3) & 0xfff;
 }
 
 static void ads7846_update_value(struct spi_message *m, int val)

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/input-ads7846-correct-the-value-got-from-spi.patch