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Commit 9084533e authored by David Brownell's avatar David Brownell Committed by Linus Torvalds
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[PATCH] ads7846 conversion accuracy 



This improves accuracy of the touchscreen and hwmon sensor readings,
addressing an issue noted by Imre Deak: there's an extra bit written before
the sample (12 bits) gets written out.

It also catches up to various comments, and makes the /proc/interrupts
entry sensible again.

Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Cc: Imre Deak <imre.deak@nokia.com>
Cc: Jean Delvare <khali@linux-fr.org>
Cc: Dmitry Torokhov <dtor_core@ameritech.net>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent f09de595

drivers/input/touchscreen/ads7846.c

+28 −25
Original line number Diff line number Diff line
@@ -36,13 +36,10 @@ 




/*

 * This code has been tested on an ads7846 / N770 device.

 * This code has been heavily tested on a Nokia 770, and lightly

 * tested on other ads7846 devices (OSK/Mistral, Lubbock).

 * Support for ads7843 and ads7845 has only been stubbed in.

 *

 * Not yet done:  How accurate are the temperature and voltage

 * readings? (System-specific calibration should support

 * accuracy of 0.3 degrees C; otherwise it's 2.0 degrees.)

 *

 * IRQ handling needs a workaround because of a shortcoming in handling

 * edge triggered IRQs on some platforms like the OMAP1/2. These

 * platforms don't handle the ARM lazy IRQ disabling properly, thus we
@@ -248,10 +245,13 @@ static int ads7846_read12_ser(struct device *dev, unsigned command) 


	if (req->msg.status)

		status = req->msg.status;



	/* on-wire is a must-ignore bit, a BE12 value, then padding */

	sample = be16_to_cpu(req->sample);

	sample = sample >> 4;

	kfree(req);

	sample = sample >> 3;

	sample &= 0x0fff;



	kfree(req);

	return status ? status : sample;

}
@@ -336,13 +336,13 @@ static void ads7846_rx(void *ads) 
	u16			x, y, z1, z2;

	unsigned long		flags;



	/* adjust:  12 bit samples (left aligned), built from

	 * two 8 bit values writen msb-first.

	/* adjust:  on-wire is a must-ignore bit, a BE12 value, then padding;

	 * built from two 8 bit values written msb-first.

	 */

	x = be16_to_cpu(ts->tc.x) >> 4;

	y = be16_to_cpu(ts->tc.y) >> 4;

	z1 = be16_to_cpu(ts->tc.z1) >> 4;

	z2 = be16_to_cpu(ts->tc.z2) >> 4;

	x = (be16_to_cpu(ts->tc.x) >> 3) & 0x0fff;

	y = (be16_to_cpu(ts->tc.y) >> 3) & 0x0fff;

	z1 = (be16_to_cpu(ts->tc.z1) >> 3) & 0x0fff;

	z2 = (be16_to_cpu(ts->tc.z2) >> 3) & 0x0fff;



	/* range filtering */

	if (x == MAX_12BIT)
@@ -420,7 +420,7 @@ static void ads7846_debounce(void *ads) 


	m = &ts->msg[ts->msg_idx];

	t = list_entry(m->transfers.prev, struct spi_transfer, transfer_list);

	val = (*(u16 *)t->rx_buf) >> 3;

	val = (be16_to_cpu(*(__be16 *)t->rx_buf) >> 3) & 0x0fff;

	if (!ts->read_cnt || (abs(ts->last_read - val) > ts->debounce_tol)) {

		/* Repeat it, if this was the first read or the read

		 * wasn't consistent enough. */
@@ -469,7 +469,7 @@ static void ads7846_timer(unsigned long handle) 
	spin_lock_irq(&ts->lock);



	if (unlikely(ts->msg_idx && !ts->pendown)) {

		/* measurment cycle ended */

		/* measurement cycle ended */

		if (!device_suspended(&ts->spi->dev)) {

			ts->irq_disabled = 0;

			enable_irq(ts->spi->irq);
@@ -495,11 +495,10 @@ static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs) 
	spin_lock_irqsave(&ts->lock, flags);

	if (likely(ts->get_pendown_state())) {

		if (!ts->irq_disabled) {

			/* REVISIT irq logic for many ARM chips has cloned a

			 * bug wherein disabling an irq in its handler won't

			 * work;(it's disabled lazily, and too late to work.

			 * until all their irq logic is fixed, we must shadow

			 * that state here.

			/* The ARM do_simple_IRQ() dispatcher doesn't act

			 * like the other dispatchers:  it will report IRQs

			 * even after they've been disabled.  We work around

			 * that here.  (The "generic irq" framework may help...)

			 */

			ts->irq_disabled = 1;

			disable_irq(ts->spi->irq);
@@ -609,16 +608,20 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
		return -EINVAL;

	}



	/* REVISIT when the irq can be triggered active-low, or if for some

	 * reason the touchscreen isn't hooked up, we don't need to access

	 * the pendown state.

	 */

	if (pdata->get_pendown_state == NULL) {

		dev_dbg(&spi->dev, "no get_pendown_state function?\n");

		return -EINVAL;

	}



	/* We'd set the wordsize to 12 bits ... except that some controllers

	 * will then treat the 8 bit command words as 12 bits (and drop the

	 * four MSBs of the 12 bit result).  Result: inputs must be shifted

	 * to discard the four garbage LSBs.

	/* We'd set TX wordsize 8 bits and RX wordsize to 13 bits ... except

	 * that even if the hardware can do that, the SPI controller driver

	 * may not.  So we stick to very-portable 8 bit words, both RX and TX.

	 */

	spi->bits_per_word = 8;



	ts = kzalloc(sizeof(struct ads7846), GFP_KERNEL);

	input_dev = input_allocate_device();
@@ -772,7 +775,7 @@ static int __devinit ads7846_probe(struct spi_device *spi) 


	if (request_irq(spi->irq, ads7846_irq,

			SA_SAMPLE_RANDOM | SA_TRIGGER_FALLING,

			spi->dev.bus_id, ts)) {

			spi->dev.driver->name, ts)) {

		dev_dbg(&spi->dev, "irq %d busy?\n", spi->irq);

		err = -EBUSY;

		goto err_free_mem;