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Input: ads7846 - extend the driver for ads7845 controller support
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ADS7845 is a controller for 5-wire touch screens and somewhat
different from 7846. It requires three serial communications to
accomplish one complete conversion. Unlike 7846 it doesn't allow
Z1-/Z2- position measurement.

The patch extends the ads7846 driver to also support ads7845.
The packet struct is extended to contain needed command and
conversion buffers. ads7846_rx() and ads7846_rx_val() now
differentiate between 7845 and 7846 case. ads7846_probe() is
modified to setup ads7845 specific command and conversion
messages and to switch ads7845 into power-down mode, since
this is needed to be prepared to respond to pendown interrupts.

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
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Anatolij Gustschin authored and Dmitry Torokhov committed Jul 3, 2010
1 parent 0f622bf commit 3eac5c7
Showing 1 changed file with 135 additions and 37 deletions.
172 changes: 135 additions & 37 deletions drivers/input/touchscreen/ads7846.c
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,8 @@ struct ts_event {
u16 y;
u16 z1, z2;
int ignore;
u8 x_buf[3];
u8 y_buf[3];
};

/*
Expand All @@ -79,6 +81,8 @@ struct ads7846_packet {
u8 read_x, read_y, read_z1, read_z2, pwrdown;
u16 dummy; /* for the pwrdown read */
struct ts_event tc;
/* for ads7845 with mpc5121 psc spi we use 3-byte buffers */
u8 read_x_cmd[3], read_y_cmd[3], pwrdown_cmd[3];
};

struct ads7846 {
Expand Down Expand Up @@ -207,6 +211,14 @@ struct ser_req {
struct spi_transfer xfer[6];
};

struct ads7845_ser_req {
u8 command[3];
u8 pwrdown[3];
u8 sample[3];
struct spi_message msg;
struct spi_transfer xfer[2];
};

static void ads7846_enable(struct ads7846 *ts);
static void ads7846_disable(struct ads7846 *ts);

Expand Down Expand Up @@ -287,6 +299,41 @@ static int ads7846_read12_ser(struct device *dev, unsigned command)
return status;
}

static int ads7845_read12_ser(struct device *dev, unsigned command)
{
struct spi_device *spi = to_spi_device(dev);
struct ads7846 *ts = dev_get_drvdata(dev);
struct ads7845_ser_req *req = kzalloc(sizeof *req, GFP_KERNEL);
int status;

if (!req)
return -ENOMEM;

spi_message_init(&req->msg);

req->command[0] = (u8) command;
req->xfer[0].tx_buf = req->command;
req->xfer[0].rx_buf = req->sample;
req->xfer[0].len = 3;
spi_message_add_tail(&req->xfer[0], &req->msg);

ts->irq_disabled = 1;
disable_irq(spi->irq);
status = spi_sync(spi, &req->msg);
ts->irq_disabled = 0;
enable_irq(spi->irq);

if (status == 0) {
/* BE12 value, then padding */
status = be16_to_cpu(*((u16 *)&req->sample[1]));
status = status >> 3;
status &= 0x0fff;
}

kfree(req);
return status;
}

#if defined(CONFIG_HWMON) || defined(CONFIG_HWMON_MODULE)

#define SHOW(name, var, adjust) static ssize_t \
Expand Down Expand Up @@ -540,17 +587,30 @@ static void ads7846_rx(void *ads)
/* ads7846_rx_val() did in-place conversion (including byteswap) from
* on-the-wire format as part of debouncing to get stable readings.
*/
x = packet->tc.x;
y = packet->tc.y;
z1 = packet->tc.z1;
z2 = packet->tc.z2;
if (ts->model == 7845) {
x = *(u16 *)packet->tc.x_buf;
y = *(u16 *)packet->tc.y_buf;
z1 = 0;
z2 = 0;
} else {
x = packet->tc.x;
y = packet->tc.y;
z1 = packet->tc.z1;
z2 = packet->tc.z2;
}

/* range filtering */
if (x == MAX_12BIT)
x = 0;

if (ts->model == 7843) {
Rt = ts->pressure_max / 2;
} else if (ts->model == 7845) {
if (get_pendown_state(ts))
Rt = ts->pressure_max / 2;
else
Rt = 0;
dev_vdbg(&ts->spi->dev, "x/y: %d/%d, PD %d\n", x, y, Rt);
} else if (likely(x && z1)) {
/* compute touch pressure resistance using equation #2 */
Rt = z2;
Expand Down Expand Up @@ -671,10 +731,14 @@ static void ads7846_rx_val(void *ads)
m = &ts->msg[ts->msg_idx];
t = list_entry(m->transfers.prev, struct spi_transfer, transfer_list);

/* adjust: on-wire is a must-ignore bit, a BE12 value, then padding;
* built from two 8 bit values written msb-first.
*/
val = be16_to_cpup((__be16 *)t->rx_buf) >> 3;
if (ts->model == 7845) {
val = be16_to_cpup((__be16 *)&(((char*)t->rx_buf)[1])) >> 3;
} else {
/* adjust: on-wire is a must-ignore bit, a BE12 value, then
* padding; built from two 8 bit values written msb-first.
*/
val = be16_to_cpup((__be16 *)t->rx_buf) >> 3;
}

action = ts->filter(ts->filter_data, ts->msg_idx, &val);
switch (action) {
Expand Down Expand Up @@ -1009,16 +1073,26 @@ static int __devinit ads7846_probe(struct spi_device *spi)

spi_message_init(m);

/* y- still on; turn on only y+ (and ADC) */
packet->read_y = READ_Y(vref);
x->tx_buf = &packet->read_y;
x->len = 1;
spi_message_add_tail(x, m);
if (ts->model == 7845) {
packet->read_y_cmd[0] = READ_Y(vref);
packet->read_y_cmd[1] = 0;
packet->read_y_cmd[2] = 0;
x->tx_buf = &packet->read_y_cmd[0];
x->rx_buf = &packet->tc.y_buf[0];
x->len = 3;
spi_message_add_tail(x, m);
} else {
/* y- still on; turn on only y+ (and ADC) */
packet->read_y = READ_Y(vref);
x->tx_buf = &packet->read_y;
x->len = 1;
spi_message_add_tail(x, m);

x++;
x->rx_buf = &packet->tc.y;
x->len = 2;
spi_message_add_tail(x, m);
x++;
x->rx_buf = &packet->tc.y;
x->len = 2;
spi_message_add_tail(x, m);
}

/* the first sample after switching drivers can be low quality;
* optionally discard it, using a second one after the signals
Expand All @@ -1044,17 +1118,28 @@ static int __devinit ads7846_probe(struct spi_device *spi)
m++;
spi_message_init(m);

/* turn y- off, x+ on, then leave in lowpower */
x++;
packet->read_x = READ_X(vref);
x->tx_buf = &packet->read_x;
x->len = 1;
spi_message_add_tail(x, m);
if (ts->model == 7845) {
x++;
packet->read_x_cmd[0] = READ_X(vref);
packet->read_x_cmd[1] = 0;
packet->read_x_cmd[2] = 0;
x->tx_buf = &packet->read_x_cmd[0];
x->rx_buf = &packet->tc.x_buf[0];
x->len = 3;
spi_message_add_tail(x, m);
} else {
/* turn y- off, x+ on, then leave in lowpower */
x++;
packet->read_x = READ_X(vref);
x->tx_buf = &packet->read_x;
x->len = 1;
spi_message_add_tail(x, m);

x++;
x->rx_buf = &packet->tc.x;
x->len = 2;
spi_message_add_tail(x, m);
x++;
x->rx_buf = &packet->tc.x;
x->len = 2;
spi_message_add_tail(x, m);
}

/* ... maybe discard first sample ... */
if (pdata->settle_delay_usecs) {
Expand Down Expand Up @@ -1145,15 +1230,25 @@ static int __devinit ads7846_probe(struct spi_device *spi)
m++;
spi_message_init(m);

x++;
packet->pwrdown = PWRDOWN;
x->tx_buf = &packet->pwrdown;
x->len = 1;
spi_message_add_tail(x, m);
if (ts->model == 7845) {
x++;
packet->pwrdown_cmd[0] = PWRDOWN;
packet->pwrdown_cmd[1] = 0;
packet->pwrdown_cmd[2] = 0;
x->tx_buf = &packet->pwrdown_cmd[0];
x->len = 3;
} else {
x++;
packet->pwrdown = PWRDOWN;
x->tx_buf = &packet->pwrdown;
x->len = 1;
spi_message_add_tail(x, m);

x++;
x->rx_buf = &packet->dummy;
x->len = 2;
}

x++;
x->rx_buf = &packet->dummy;
x->len = 2;
CS_CHANGE(*x);
spi_message_add_tail(x, m);

Expand Down Expand Up @@ -1202,8 +1297,11 @@ static int __devinit ads7846_probe(struct spi_device *spi)
/* take a first sample, leaving nPENIRQ active and vREF off; avoid
* the touchscreen, in case it's not connected.
*/
(void) ads7846_read12_ser(&spi->dev,
READ_12BIT_SER(vaux) | ADS_PD10_ALL_ON);
if (ts->model == 7845)
ads7845_read12_ser(&spi->dev, PWRDOWN);
else
(void) ads7846_read12_ser(&spi->dev,
READ_12BIT_SER(vaux) | ADS_PD10_ALL_ON);

err = sysfs_create_group(&spi->dev.kobj, &ads784x_attr_group);
if (err)
Expand Down

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