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Subject[GIT PATCH 5/6] ads7846: assorted updates
From: David Brownell <dbrownell@users.sourceforge.net>

Input: ads7846 - assorted updates

This updates the ads7846 touchscreen driver:
- to allow faster clocking (this driver doesn't push sample rates);
- bugfixes the conversion of spi_transfer to lists;
- some dma-unsafe command buffers are fixed.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
---
drivers/input/touchscreen/ads7846.c | 68 +++++++++++++++++++++++-------------
1 files changed, 44 insertions(+), 24 deletions(-)
Index: work/drivers/input/touchscreen/ads7846.c
===================================================================
--- work.orig/drivers/input/touchscreen/ads7846.c
+++ work/drivers/input/touchscreen/ads7846.c
@@ -48,10 +48,13 @@

#define TS_POLL_PERIOD msecs_to_jiffies(10)

+/* this driver doesn't aim at the peak continuous sample rate */
+#define SAMPLE_BITS (8 /*cmd*/ + 16 /*sample*/ + 2 /* before, after */)
+
struct ts_event {
/* For portability, we can't read 12 bit values using SPI (which
* would make the controller deliver them as native byteorder u16
- * with msbs zeroed). Instead, we read them as two 8-byte values,
+ * with msbs zeroed). Instead, we read them as two 8-bit values,
* which need byteswapping then range adjustment.
*/
__be16 x;
@@ -68,6 +71,7 @@ struct ads7846 {
u16 vref_delay_usecs;
u16 x_plate_ohms;

+ u8 read_x, read_y, read_z1, read_z2;
struct ts_event tc;

struct spi_transfer xfer[8];
@@ -117,10 +121,10 @@ struct ads7846 {
#define READ_12BIT_DFR(x) (ADS_START | ADS_A2A1A0_d_ ## x \
| ADS_12_BIT | ADS_DFR)

-static const u8 read_y = READ_12BIT_DFR(y) | ADS_PD10_ADC_ON;
-static const u8 read_z1 = READ_12BIT_DFR(z1) | ADS_PD10_ADC_ON;
-static const u8 read_z2 = READ_12BIT_DFR(z2) | ADS_PD10_ADC_ON;
-static const u8 read_x = READ_12BIT_DFR(x) | ADS_PD10_PDOWN; /* LAST */
+#define READ_Y (READ_12BIT_DFR(y) | ADS_PD10_ADC_ON)
+#define READ_Z1 (READ_12BIT_DFR(z1) | ADS_PD10_ADC_ON)
+#define READ_Z2 (READ_12BIT_DFR(z2) | ADS_PD10_ADC_ON)
+#define READ_X (READ_12BIT_DFR(x) | ADS_PD10_PDOWN) /* LAST */

/* single-ended samples need to first power up reference voltage;
* we leave both ADC and VREF powered
@@ -128,8 +132,8 @@ static const u8 read_x = READ_12BIT_DFR
#define READ_12BIT_SER(x) (ADS_START | ADS_A2A1A0_ ## x \
| ADS_12_BIT | ADS_SER)

-static const u8 ref_on = READ_12BIT_DFR(x) | ADS_PD10_ALL_ON;
-static const u8 ref_off = READ_12BIT_DFR(y) | ADS_PD10_PDOWN;
+#define REF_ON (READ_12BIT_DFR(x) | ADS_PD10_ALL_ON)
+#define REF_OFF (READ_12BIT_DFR(y) | ADS_PD10_PDOWN)

/*--------------------------------------------------------------------------*/

@@ -138,7 +142,9 @@ static const u8 ref_off = READ_12BIT_DFR
*/

struct ser_req {
+ u8 ref_on;
u8 command;
+ u8 ref_off;
u16 scratch;
__be16 sample;
struct spi_message msg;
@@ -160,7 +166,8 @@ static int ads7846_read12_ser(struct dev
INIT_LIST_HEAD(&req->msg.transfers);

/* activate reference, so it has time to settle; */
- req->xfer[0].tx_buf = &ref_on;
+ req->ref_on = REF_ON;
+ req->xfer[0].tx_buf = &req->ref_on;
req->xfer[0].len = 1;
req->xfer[1].rx_buf = &req->scratch;
req->xfer[1].len = 2;
@@ -182,7 +189,8 @@ static int ads7846_read12_ser(struct dev
/* REVISIT: take a few more samples, and compare ... */

/* turn off reference */
- req->xfer[4].tx_buf = &ref_off;
+ req->ref_off = REF_OFF;
+ req->xfer[4].tx_buf = &req->ref_off;
req->xfer[4].len = 1;
req->xfer[5].rx_buf = &req->scratch;
req->xfer[5].len = 2;
@@ -400,7 +408,6 @@ static int __devinit ads7846_probe(struc
struct input_dev *input_dev;
struct ads7846_platform_data *pdata = spi->dev.platform_data;
struct spi_transfer *x;
- int i;
int err;

if (!spi->irq) {
@@ -414,9 +421,9 @@ static int __devinit ads7846_probe(struc
}

/* don't exceed max specified sample rate */
- if (spi->max_speed_hz > (125000 * 16)) {
+ if (spi->max_speed_hz > (125000 * SAMPLE_BITS)) {
dev_dbg(&spi->dev, "f(sample) %d KHz?\n",
- (spi->max_speed_hz/16)/1000);
+ (spi->max_speed_hz/SAMPLE_BITS)/1000);
return -EINVAL;
}

@@ -469,45 +476,58 @@ static int __devinit ads7846_probe(struc
/* set up the transfers to read touchscreen state; this assumes we
* use formula #2 for pressure, not #3.
*/
+ INIT_LIST_HEAD(&ts->msg.transfers);
x = ts->xfer;

/* y- still on; turn on only y+ (and ADC) */
- x->tx_buf = &read_y;
+ ts->read_y = READ_Y;
+ x->tx_buf = &ts->read_y;
x->len = 1;
+ spi_message_add_tail(x, &ts->msg);
+
x++;
x->rx_buf = &ts->tc.y;
x->len = 2;
- x++;
+ spi_message_add_tail(x, &ts->msg);

/* turn y+ off, x- on; we'll use formula #2 */
if (ts->model == 7846) {
- x->tx_buf = &read_z1;
+ x++;
+ ts->read_z1 = READ_Z1;
+ x->tx_buf = &ts->read_z1;
x->len = 1;
+ spi_message_add_tail(x, &ts->msg);
+
x++;
x->rx_buf = &ts->tc.z1;
x->len = 2;
- x++;
+ spi_message_add_tail(x, &ts->msg);

- x->tx_buf = &read_z2;
+ x++;
+ ts->read_z2 = READ_Z2;
+ x->tx_buf = &ts->read_z2;
x->len = 1;
+ spi_message_add_tail(x, &ts->msg);
+
x++;
x->rx_buf = &ts->tc.z2;
x->len = 2;
- x++;
+ spi_message_add_tail(x, &ts->msg);
}

/* turn y- off, x+ on, then leave in lowpower */
- x->tx_buf = &read_x;
+ x++;
+ ts->read_x = READ_X;
+ x->tx_buf = &ts->read_x;
x->len = 1;
+ spi_message_add_tail(x, &ts->msg);
+
x++;
x->rx_buf = &ts->tc.x;
x->len = 2;
- x++;
-
- CS_CHANGE(x[-1]);
+ CS_CHANGE(*x);
+ spi_message_add_tail(x, &ts->msg);

- for (i = 0; i < x - ts->xfer; i++)
- spi_message_add_tail(&ts->xfer[i], &ts->msg);
ts->msg.complete = ads7846_rx;
ts->msg.context = ts;

-
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