linux-kernel - [PATCH 2/2] tsc2007: reduced number of I2C transfers

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Date:	Fri, 24 Jul 2009 18:14:37 +0200
From:	Richard Röjfors 
	<richard.rojfors.ext@...ean-labs.com>
To:	linux-input@...r.kernel.org
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	kwangwoo.lee@...il.com,
	Thierry Reding <thierry.reding@...onic-design.de>,
	Trilok Soni <soni.trilok@...il.com>
Subject: [PATCH 2/2] tsc2007: reduced number of I2C transfers

Decreases the number of I2C transactions transferred by the driver.
During probe we don't need to ask for the coordinates from the controller.
When polling the controller we don't need to power down and enable IRQ 
if we are going to poll again.

Signed-off-by: Richard Röjfors <richard.rojfors.ext@...ean-labs.com>
---
Index: linux-2.6.31-rc2/drivers/input/touchscreen/tsc2007.c
===================================================================
--- linux-2.6.31-rc2/drivers/input/touchscreen/tsc2007.c	(revision 1040)
+++ linux-2.6.31-rc2/drivers/input/touchscreen/tsc2007.c	(revision 1053)
@@ -178,6 +178,12 @@
  		ts->penstate = PEN_STATE_UP;
  }

+static void tsc2007_power_down(struct tsc2007 *tsc)
+{
+	/* power down */
+	tsc2007_xfer(tsc, PWRDOWN);
+}
+
  static int tsc2007_read_values(struct tsc2007 *tsc)
  {
  	/* y- still on; turn on only y+ (and ADC) */
@@ -188,11 +194,8 @@

  	/* turn y+ off, x- on; we'll use formula #1 */
  	tsc->tc.z1 = tsc2007_xfer(tsc, READ_Z1);
-	tsc->tc.z2 = tsc2007_xfer(tsc, READ_Z2);
+	tsc->tc.z2 = tsc2007_xfer(tsc, READ_Z2 | TSC2007_POWER_OFF_IRQ_EN);

-	/* power down */
-	tsc2007_xfer(tsc, PWRDOWN);
-
  	return 0;
  }

@@ -217,6 +220,7 @@
  		input_sync(input);

  		ts->penstate = PEN_STATE_UP;
+		tsc2007_power_down(ts);
  		enable_irq(ts->irq);
  	} else {
  		/* pen is still down, continue with the measurement */
@@ -305,7 +309,7 @@
  	input_set_abs_params(input_dev, ABS_Y, 0, MAX_12BIT, 0, 0);
  	input_set_abs_params(input_dev, ABS_PRESSURE, 0, MAX_12BIT, 0, 0);

-	tsc2007_read_values(ts);
+	tsc2007_power_down(ts);

  	ts->irq = client->irq;
--
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