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Subject[PATCH v2 2/4] da850-evm: add UI Expander pushbuttons
Date
This patch adds EV_KEYs for each of the 8 pushbuttons on the UI board via a
gpio-key device.

The expander is a tca6416; it controls the SEL_{A,B,C} lines which enable and
disable the peripherals found on the UI board in addition to the 8 pushbuttons
mentioned above. The reason the existing tca6416-keypad driver is not employed
is because there was no aparent way to keep the gpio lines used as
SEL_{A,B,C} registered while simultaneously registering the pushbuttons as a
tca6416-keypad instance.
Some experimentation with the polling interval was performed; we were searching
for the largest polling interval that did not affect the feel of the
responsiveness of the buttons. It is very subjective but 200ms seems to be a
good value that accepts firm pushes but rejects very light ones. The key values
assigned to the buttons were arbitrarily chosen to be F1-F8.

Signed-off-by: Ben Gardiner <bengardiner@nanometrics.ca>
Reviewed-by: Chris Cordahi <christophercordahi@nanometrics.ca>
CC: Govindarajan, Sriramakrishnan <srk@ti.com>

---
Changes since v1:
* set INPUT_POLLDEV default for DA850_EVM machine, but don't select it
unconditionally
* adding note to description about why tca6416-keypad was not used
* adding Govindarajan, Sriramakrishnan, the author of the tca6416-keypad
driver
---
arch/arm/mach-davinci/Kconfig | 3 +
arch/arm/mach-davinci/board-da850-evm.c | 76 +++++++++++++++++++++++++++++++
2 files changed, 79 insertions(+), 0 deletions(-)
diff --git a/arch/arm/mach-davinci/Kconfig b/arch/arm/mach-davinci/Kconfig
index b77b860..5163a1c 100644
--- a/arch/arm/mach-davinci/Kconfig
+++ b/arch/arm/mach-davinci/Kconfig
@@ -178,6 +178,9 @@ config DA850_UI_RMII

endchoice

+config INPUT_POLLDEV
+ default MACH_DAVINCI_DA850_EVM
+
config MACH_TNETV107X
bool "TI TNETV107X Reference Platform"
default ARCH_DAVINCI_TNETV107X
diff --git a/arch/arm/mach-davinci/board-da850-evm.c b/arch/arm/mach-davinci/board-da850-evm.c
index c6e11c6..ff71ffd 100644
--- a/arch/arm/mach-davinci/board-da850-evm.c
+++ b/arch/arm/mach-davinci/board-da850-evm.c
@@ -17,8 +17,10 @@
#include <linux/i2c.h>
#include <linux/i2c/at24.h>
#include <linux/i2c/pca953x.h>
+#include <linux/input.h>
#include <linux/mfd/tps6507x.h>
#include <linux/gpio.h>
+#include <linux/gpio_keys.h>
#include <linux/platform_device.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/nand.h>
@@ -272,6 +274,63 @@ static inline void da850_evm_setup_emac_rmii(int rmii_sel)
static inline void da850_evm_setup_emac_rmii(int rmii_sel) { }
#endif

+
+#define DA850_PB_DEBOUNCE_MS 10
+/*
+ * At 200ms polling interval it is possible to miss an
+ * event by tapping very lightly on the push button but most
+ * pushes do result in an event; longer intervals require the
+ * user to hold the button whereas shorter intervals require
+ * more CPU time for polling.
+ */
+#define DA850_PB_POLL_MS 200
+/* No need to poll switches anywhere near as fast */
+#define DA850_SW_POLL_MS 700
+
+static const char const *ui_expander_names[] = {
+ "dgnd", "dgnd", "dgnd", "dgnd", "nc", "sel_c", "sel_b", "sel_a", "pb8",
+ "pb7", "pb6", "pb5", "pb4", "pb3", "pb2", "pb1"
+};
+
+#define DA850_UI_PB8_OFFSET 8
+#define DA850_N_UI_PB 8
+
+static struct gpio_keys_button user_ui_pbs_gpio_keys[DA850_N_UI_PB];
+
+static struct gpio_keys_platform_data user_ui_pbs_gpio_key_platform_data = {
+ .buttons = user_ui_pbs_gpio_keys,
+ .nbuttons = ARRAY_SIZE(user_ui_pbs_gpio_keys),
+ .rep = 0, /* disable auto-repeat */
+ .poll_interval = DA850_PB_POLL_MS,
+};
+
+static struct platform_device user_ui_pb_gpio_key_device = {
+ .name = "gpio-keys",
+ .id = 0,
+ .dev = {
+ .platform_data = &user_ui_pbs_gpio_key_platform_data
+ }
+};
+
+static void da850_ui_pushbuttons_init(unsigned gpio)
+{
+ int i;
+ struct gpio_keys_button *button;
+
+ for (i = 0; i < DA850_N_UI_PB; i++) {
+ button = &user_ui_pbs_gpio_keys[i];
+
+ button->code = KEY_F8 - i;
+ button->type = EV_KEY;
+ button->active_low = 1;
+ button->wakeup = 0;
+ button->debounce_interval = DA850_PB_DEBOUNCE_MS;
+ button->desc = (char *)
+ ui_expander_names[DA850_UI_PB8_OFFSET + i];
+ button->gpio = gpio + DA850_UI_PB8_OFFSET + i;
+ }
+}
+
static int da850_evm_ui_expander_setup(struct i2c_client *client, unsigned gpio,
unsigned ngpio, void *c)
{
@@ -304,6 +363,14 @@ static int da850_evm_ui_expander_setup(struct i2c_client *client, unsigned gpio,
gpio_direction_output(sel_b, 1);
gpio_direction_output(sel_c, 1);

+ da850_ui_pushbuttons_init(gpio);
+ ret = platform_device_register(&user_ui_pb_gpio_key_device);
+ if (ret) {
+ pr_warning("Could not register UI GPIO expander push-buttons"
+ " device\n");
+ goto exp_setup_keys_fail;
+ }
+
ui_card_detected = 1;
pr_info("DA850/OMAP-L138 EVM UI card detected\n");

@@ -313,6 +380,8 @@ static int da850_evm_ui_expander_setup(struct i2c_client *client, unsigned gpio,

return 0;

+exp_setup_keys_fail:
+ gpio_free(sel_c);
exp_setup_selc_fail:
gpio_free(sel_b);
exp_setup_selb_fail:
@@ -324,6 +393,8 @@ exp_setup_sela_fail:
static int da850_evm_ui_expander_teardown(struct i2c_client *client,
unsigned gpio, unsigned ngpio, void *c)
{
+ platform_device_unregister(&user_ui_pb_gpio_key_device);
+
/* deselect all functionalities */
gpio_set_value(gpio + 5, 1);
gpio_set_value(gpio + 6, 1);
@@ -340,6 +411,7 @@ static struct pca953x_platform_data da850_evm_ui_expander_info = {
.gpio_base = DAVINCI_N_GPIO,
.setup = da850_evm_ui_expander_setup,
.teardown = da850_evm_ui_expander_teardown,
+ .names = ui_expander_names,
};

static struct i2c_board_info __initdata da850_evm_i2c_devices[] = {
@@ -349,6 +421,10 @@ static struct i2c_board_info __initdata da850_evm_i2c_devices[] = {
{
I2C_BOARD_INFO("tca6416", 0x20),
.platform_data = &da850_evm_ui_expander_info,
+ /*
+ * TODO : populate at runtime using
+ * .irq = gpio_to_irq(GPIO_TO_PIN(2,7)),
+ */
},
};

--
1.7.0.4


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