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[PATCH 3.14 22/23] Input: ads7846 - correct the value got from SPI

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3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andrey Gelman <andrey.gelman@compulab.co.il>

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.

Signed-off-by: Andrey Gelman <andrey.gelman@compulab.co.il>
Signed-off-by: Haibo Chen <haibo.chen@freescale.com>
Signed-off-by: Igor Grinberg <grinberg@compulab.co.il>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -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)

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[PATCH 3.14 00/23] 3.14.69-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 21/23] iio: ak8975: Fix NULL pointer exception on early interrupt Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 07/23] lpfc: fix misleading indentation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 04/23] ipvs: correct initial offset of Call-ID header search in SIP persistence engine Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 22/23] Input: ads7846 - correct the value got from SPI Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 01/23] compiler-gcc: integrate the various compiler-gcc[345].h files Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
    Re: [PATCH 3.14 01/23] compiler-gcc: integrate the various  compiler-gcc[345].h files Jiri Slaby <jslaby@suse.cz> - 2016-05-11 11:30 +0200
  [PATCH 3.14 20/23] USB: serial: cp210x: add Straizona Focusers device ids Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 16/23] x86/tsc: Read all ratio bits from MSR_PLATFORM_INFO Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 23/23] powerpc: scan_features() updates incorrect bits for REAL_LE Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 19/23] USB: serial: cp210x: add ID for Link ECU Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 12/23] batman-adv: Check skb size before using encapsulated ETH+VLAN header Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 10/23] Input: zforce_ts - fix dual touch recognition Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 09:20 +0200
  [PATCH 3.14 09/23] ARM: SoCFPGA: Fix secondary CPU startup in thumb2 kernel Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 10:00 +0200
  [PATCH 3.14 18/23] ACPICA: Dispatcher: Update thread ID for recursive method calls Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 10:10 +0200
  [PATCH 3.14 15/23] MAINTAINERS: Remove asterisk from EFI directory names Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 10:10 +0200
  [PATCH 3.14 11/23] proc: prevent accessing /proc/<PID>/environ until its ready Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 10:10 +0200
  [PATCH 3.14 08/23] tracing: Dont display trigger file for events that cant be enabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 10:10 +0200
  [PATCH 3.14 17/23] x86/sysfb_efi: Fix valid BAR address range check Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 10:10 +0200
  [PATCH 3.14 05/23] nbd: ratelimit error msgs after socket close Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 10:10 +0200
  [PATCH 3.14 02/23] compiler-gcc: disable -ftracer for __noclone functions Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-09 10:10 +0200
  Re: [PATCH 3.14 00/23] 3.14.69-stable review Guenter Roeck <linux@roeck-us.net> - 2016-05-09 15:30 +0200
  Re: [PATCH 3.14 00/23] 3.14.69-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2016-05-09 21:50 +0200

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