linux-kernel - [PATCH] [RFC] ads7846: force driver to work with ads7845

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Message-ID: <20150518125500.GA22524@fifteen>
Date:	Mon, 18 May 2015 15:55:00 +0300
From:	Evgeniy Dushistov <dushistov@...l.ru>
To:	Anatolij Gustschin <agust@...x.de>, Dmitry Torokhov <dtor@...l.ru>
Cc:	Jingoo Han <jg1.han@...sung.com>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] [RFC] ads7846: force driver to work with ads7845

CC me please, I'm not subscribed to any linux-kernel list.

Hi,
recently I have ads7845 device connected to my beagleboard,
and I try to use ads7846 to work with it.
But it fails, it show completely wrong x/y.

But, after I disabled almost all code that related to ads7845 ("== 7845"),
except determination of amount of pressure force,
all start works as expected,
I found such commit:

>commit 3eac5c7e44f35eb07f0ecb28ce60f15b2dda1932
>Author: Anatolij Gustschin <agust@...x.de>
>...
>ADS7845 is a controller for 5-wire touch screens and somewhat
>different from 7846. It requires three serial communications to
>accomplish one complete conversion.
>...

But according to datasheets:
http://www.ti.com/lit/ds/symlink/ads7846.pdf
http://www.ti.com/lit/ds/symlink/ads7845.pdf

ads7845(page 8) and ads7846 (page 12) have
identical digital interfaces, I attach quotes
from them in text from to this email.

So why spi negotiation for ads7845 require special code,
except
>Z1-/Z2- position measurement

Was this commit tested? May be you test
in some special mode, like 15 vs 16 bits?

Here is working for me patch (it against 3.16,
but applied to Linus's git master also).

ads7846: fix to force ads7846 driver works with ads7845
 device

Signed-off-by: Evgneiy A. Dushistov <dushistov@...l.ru>
---
 drivers/input/touchscreen/ads7846.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index da201b8..27f4796 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -17,6 +17,9 @@
  *  it under the terms of the GNU General Public License version 2 as
  *  published by the Free Software Foundation.
  */
+#define VERBOSE_DEBUG
+#define DEBUG
+
 #include <linux/types.h>
 #include <linux/hwmon.h>
 #include <linux/err.h>
@@ -671,14 +674,14 @@ static int ads7846_get_value(struct ads7846 *ts, struct spi_message *m)
 	struct spi_transfer *t =
 		list_entry(m->transfers.prev, struct spi_transfer, transfer_list);
 
-	if (ts->model == 7845) {
+	if (0/*ts->model == 7845*/) {
 		return be16_to_cpup((__be16 *)&(((char*)t->rx_buf)[1])) >> 3;
 	} 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;
+		return (be16_to_cpup((__be16 *)t->rx_buf) & 0x7fff) >> 3;
 	}
 }
 
@@ -755,14 +758,12 @@ static void ads7846_report_state(struct ads7846 *ts)
 	 * from on-the-wire format as part of debouncing to get stable
 	 * readings.
 	 */
+	x = packet->tc.x;
+	y = packet->tc.y;
 	if (ts->model == 7845) {
-		x = *(u16 *)packet->tc.x_buf;
-		y = *(u16 *)packet->tc.y_buf;
 		z1 = 0;
 		z2 = 0;
 	} else {
-		x = packet->tc.x;
-		y = packet->tc.y;
 		z1 = packet->tc.z1;
 		z2 = packet->tc.z2;
 	}
@@ -995,7 +996,7 @@ static void ads7846_setup_spi_msg(struct ads7846 *ts,
 	spi_message_init(m);
 	m->context = ts;
 
-	if (ts->model == 7845) {
+	if (0/*ts->model == 7845*/) {
 		packet->read_y_cmd[0] = READ_Y(vref);
 		packet->read_y_cmd[1] = 0;
 		packet->read_y_cmd[2] = 0;
@@ -1040,7 +1041,7 @@ static void ads7846_setup_spi_msg(struct ads7846 *ts,
 	spi_message_init(m);
 	m->context = ts;
 
-	if (ts->model == 7845) {
+	if (0/*ts->model == 7845*/) {
 		x++;
 		packet->read_x_cmd[0] = READ_X(vref);
 		packet->read_x_cmd[1] = 0;
@@ -1149,7 +1150,7 @@ static void ads7846_setup_spi_msg(struct ads7846 *ts,
 	spi_message_init(m);
 	m->context = ts;
 
-	if (ts->model == 7845) {
+	if (0/*ts->model == 7845*/) {
 		x++;
 		packet->pwrdown_cmd[0] = PWRDOWN;
 		packet->pwrdown_cmd[1] = 0;
@@ -1408,7 +1409,7 @@ static int ads7846_probe(struct spi_device *spi)
 	 * Take a first sample, leaving nPENIRQ active and vREF off; avoid
 	 * the touchscreen, in case it's not connected.
 	 */
-	if (ts->model == 7845)
+	if (0/*ts->model == 7845*/)
 		ads7845_read12_ser(&spi->dev, PWRDOWN);
 	else
 		(void) ads7846_read12_ser(&spi->dev, READ_12BIT_SER(vaux));
-- 
2.3.6

-- 
/Evgeniy

View attachment "1_1.txt" of type "text/plain" (1369 bytes)

View attachment "2_1.txt" of type "text/plain" (1438 bytes)