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[PATCH] ads7846 conversion accuracy

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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: David 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: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
David Brownell 2006-05-25 18:44:20 -07:00 committed by Linus Torvalds
parent f09de595b5
commit 9084533e79
1 changed files with 29 additions and 26 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

55
drivers/input/touchscreen/ads7846.c
View file

@ -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;
sample = be16_to_cpu(req->sample);
sample = sample >> 4;
kfree(req);
/* on-wire is a must-ignore bit, a BE12 value, then padding */
sample = be16_to_cpu(req->sample);
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;