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ARM: pxa: magician: Add support for ADS7846 touchscreen

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This patch adds a support for ADS7846 touchscreen driver.

The basic functionality was tested, x_plate_ohms and y_plate_ohms were
physically measured. The value pressure_max was empirically set to match
the measured range, which is affected by x_plate_ohms and ADS samples.

The value of keep_vref_on should be set. A tested model (T-Mobile MDA
Compact PM10A) doesn't seem to use Vref pin as the input from an external
source. On this model the unset keep_vref_on cause high jitter of measured
values.

SPI framing pin (gpio_cs) must be used in GPIO mode due to an incompatible
autoframing of PXA27x controller and ADS7846 device.

Signed-off-by: Petr Cvek <petr.cvek@tul.cz>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
This commit is contained in:
Petr Cvek 2017-03-13 09:05:49 +01:00 committed by Robert Jarzmik
parent 2ea659a9ef
commit 7ade445c26
2 changed files with 84 additions and 1 deletions
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1
arch/arm/mach-pxa/include/mach/magician.h
View file

@ -24,6 +24,7 @@
#define GPIO10_MAGICIAN_GSM_IRQ 10
#define GPIO11_MAGICIAN_GSM_OUT1 11
#define GPIO13_MAGICIAN_CPLD_IRQ 13
#define GPIO14_MAGICIAN_TSC2046_CS 14
#define GPIO18_MAGICIAN_UNKNOWN 18
#define GPIO22_MAGICIAN_VIBRA_EN 22
#define GPIO26_MAGICIAN_GSM_POWER 26

84
arch/arm/mach-pxa/magician.c
View file

@ -54,6 +54,10 @@
#include "devices.h"
#include "generic.h"
#include <linux/spi/spi.h>
#include <linux/spi/pxa2xx_spi.h>
#include <linux/spi/ads7846.h>
static unsigned long magician_pin_config[] __initdata = {
/* SDRAM and Static Memory I/O Signals */
@ -85,7 +89,7 @@ static unsigned long magician_pin_config[] __initdata = {
/* SSP 2 TSC2046 touchscreen */
GPIO19_SSP2_SCLK,
GPIO14_SSP2_SFRM,
MFP_CFG_OUT(GPIO14, AF0, DRIVE_HIGH), /* frame as GPIO */
GPIO89_SSP2_TXD,
GPIO88_SSP2_RXD,
@ -674,6 +678,37 @@ static struct platform_device bq24022 = {
},
};
/*
* fixed regulator for ads7846
*/
static struct regulator_consumer_supply ads7846_supply =
REGULATOR_SUPPLY("vcc", "spi2.0");
static struct regulator_init_data vads7846_regulator = {
.constraints = {
.valid_ops_mask = REGULATOR_CHANGE_STATUS,
},
.num_consumer_supplies = 1,
.consumer_supplies = &ads7846_supply,
};
static struct fixed_voltage_config vads7846 = {
.supply_name = "vads7846",
.microvolts = 3300000, /* probably */
.gpio = -EINVAL,
.startup_delay = 0,
.init_data = &vads7846_regulator,
};
static struct platform_device vads7846_device = {
.name = "reg-fixed-voltage",
.id = -1,
.dev = {
.platform_data = &vads7846,
},
};
/*
* Vcore regulator MAX1587A
*/
@ -851,6 +886,49 @@ static struct i2c_pxa_platform_data magician_i2c_power_info = {
.fast_mode = 1,
};
/*
* Touchscreen
*/
static struct ads7846_platform_data ads7846_pdata = {
.model = 7846,
.x_plate_ohms = 317,
.y_plate_ohms = 500,
.pressure_max = 1023, /* with x plate ohms it will overflow 255 */
.debounce_max = 3, /* first readout is always bad */
.debounce_tol = 30,
.debounce_rep = 0,
.gpio_pendown = GPIO115_MAGICIAN_nPEN_IRQ,
.keep_vref_on = 1,
.wakeup = true,
.vref_delay_usecs = 100,
.penirq_recheck_delay_usecs = 100,
};
struct pxa2xx_spi_chip tsc2046_chip_info = {
.tx_threshold = 1,
.rx_threshold = 2,
.timeout = 64,
/* NOTICE must be GPIO, incompatibility with hw PXA SPI framing */
.gpio_cs = GPIO14_MAGICIAN_TSC2046_CS,
};
static struct pxa2xx_spi_master magician_spi_info = {
.num_chipselect = 1,
.enable_dma = 1,
};
static struct spi_board_info ads7846_spi_board_info[] __initdata = {
{
.modalias = "ads7846",
.bus_num = 2,
.max_speed_hz = 2500000,
.platform_data = &ads7846_pdata,
.controller_data = &tsc2046_chip_info,
.irq = PXA_GPIO_TO_IRQ(GPIO115_MAGICIAN_nPEN_IRQ),
},
};
/*
* Platform devices
*/
@ -865,6 +943,7 @@ static struct platform_device *devices[] __initdata = {
&power_supply,
&strataflash,
&leds_gpio,
&vads7846_device,
};
static struct gpio magician_global_gpios[] = {
@ -922,6 +1001,9 @@ static void __init magician_init(void)
} else
pr_err("LCD detection: CPLD mapping failed\n");
pxa2xx_set_spi_info(2, &magician_spi_info);
spi_register_board_info(ARRAY_AND_SIZE(ads7846_spi_board_info));
regulator_register_always_on(0, "power", pwm_backlight_supply,
ARRAY_SIZE(pwm_backlight_supply), 5000000);