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

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Date:	Fri, 24 Jul 2009 21:37:27 +0200
From:	Richard Röjfors 
	<richard.rojfors.ext@...ean-labs.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	linux-input@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	kwangwoo.lee@...il.com,
	Thierry Reding <thierry.reding@...onic-design.de>,
	Trilok Soni <soni.trilok@...il.com>
Subject: Re: [PATCH 2/2] tsc2007: reduced number of I2C transfers

On 7/24/09 8:00 PM, Dmitry Torokhov wrote:
> On Fri, Jul 24, 2009 at 06:14:37PM +0200, Richard Röjfors wrote:
>> 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);
>
> I think this leaves the controller powered on and with with PENIRQ
> disabled.
>

You are right, I think we should leave the patch like below, just get 
rid of the unnecessary read during startup.

--Richard

Input: tsc2007: Do not read coordinated when probing driver

From: Richard Röjfors <richard.rojfors.ext@...ean-labs.com>

Don't read coordinates during probe of the driver, just powering down 
the controller and wait for interrupts.


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 1056)
@@ -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) */
@@ -190,8 +196,7 @@
  	tsc->tc.z1 = tsc2007_xfer(tsc, READ_Z1);
  	tsc->tc.z2 = tsc2007_xfer(tsc, READ_Z2);

-	/* power down */
-	tsc2007_xfer(tsc, PWRDOWN);
+	tsc2007_power_down(tsc);

  	return 0;
  }
@@ -305,7 +310,7 @@
  	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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