backlight: add support for Pandora backlight

Add support for pandora (openpandora.org) backlight.

It might look like all this could be done using pwm_bl.c instead, but
there is a need of special programming sequence when turning on the LED
driver chip or else it will misbehave.  Doing this using pwm_bl.c would
require to use some register programming and pwm functions from platform
code, and ARM maintainers are allergic to driver-like code in /arch/arm
nowadays.  The PMIC PWM driver is currently missing too, so pwm_bl.c
can't be used anyway.

Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 179 insertions, 0 deletions

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 248d6c0858dd..ed68fde54454 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -348,6 +348,13 @@ config BACKLIGHT_OT200
           To compile this driver as a module, choose M here: the module will be
           called ot200_bl.
 
+config BACKLIGHT_PANDORA
+        tristate "Backlight driver for Pandora console"
+        depends on TWL4030_CORE
+        help
+          If you have a Pandora console, say Y to enable the
+          backlight driver.
+
 endif # BACKLIGHT_CLASS_DEVICE
 
 endif # BACKLIGHT_LCD_SUPPORT
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index c71dd793363d..8071eb656147 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -24,6 +24,7 @@ obj-$(CONFIG_BACKLIGHT_HP680)	+= hp680_bl.o
 obj-$(CONFIG_BACKLIGHT_LOCOMO)  += locomolcd.o
 obj-$(CONFIG_BACKLIGHT_LP855X)  += lp855x_bl.o
 obj-$(CONFIG_BACKLIGHT_OMAP1)   += omap1_bl.o
+obj-$(CONFIG_BACKLIGHT_PANDORA) += pandora_bl.o
 obj-$(CONFIG_BACKLIGHT_PROGEAR) += progear_bl.o
 obj-$(CONFIG_BACKLIGHT_CARILLO_RANCH) += cr_bllcd.o
 obj-$(CONFIG_BACKLIGHT_PWM)     += pwm_bl.o
diff --git a/drivers/video/backlight/pandora_bl.c b/drivers/video/backlight/pandora_bl.c
new file mode 100644
index 000000000000..4ec30748b447
--- /dev/null
+++ b/drivers/video/backlight/pandora_bl.c
@@ -0,0 +1,171 @@
+/*
+ * Backlight driver for Pandora handheld.
+ * Pandora uses TWL4030 PWM0 -> TPS61161 combo for control backlight.
+ * Based on pwm_bl.c
+ *
+ * Copyright 2009,2012 Gražvydas Ignotas <notasas@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/delay.h>
+#include <linux/fb.h>
+#include <linux/backlight.h>
+#include <linux/i2c/twl.h>
+#include <linux/err.h>
+
+#define TWL_PWM0_ON             0x00
+#define TWL_PWM0_OFF            0x01
+
+#define TWL_INTBR_GPBR1         0x0c
+#define TWL_INTBR_PMBR1         0x0d
+
+#define TWL_PMBR1_PWM0_MUXMASK  0x0c
+#define TWL_PMBR1_PWM0          0x04
+#define PWM0_CLK_ENABLE         BIT(0)
+#define PWM0_ENABLE             BIT(2)
+
+/* range accepted by hardware */
+#define MIN_VALUE 9
+#define MAX_VALUE 63
+#define MAX_USER_VALUE (MAX_VALUE - MIN_VALUE)
+
+#define PANDORABL_WAS_OFF BL_CORE_DRIVER1
+
+static int pandora_backlight_update_status(struct backlight_device *bl)
+{
+        int brightness = bl->props.brightness;
+        u8 r;
+
+        if (bl->props.power != FB_BLANK_UNBLANK)
+                brightness = 0;
+        if (bl->props.state & BL_CORE_FBBLANK)
+                brightness = 0;
+        if (bl->props.state & BL_CORE_SUSPENDED)
+                brightness = 0;
+
+        if ((unsigned int)brightness > MAX_USER_VALUE)
+                brightness = MAX_USER_VALUE;
+
+        if (brightness == 0) {
+                if (bl->props.state & PANDORABL_WAS_OFF)
+                        goto done;
+
+                /* first disable PWM0 output, then clock */
+                twl_i2c_read_u8(TWL4030_MODULE_INTBR, &r, TWL_INTBR_GPBR1);
+                r &= ~PWM0_ENABLE;
+                twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);
+                r &= ~PWM0_CLK_ENABLE;
+                twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);
+
+                goto done;
+        }
+
+        if (bl->props.state & PANDORABL_WAS_OFF) {
+                /*
+                 * set PWM duty cycle to max. TPS61161 seems to use this
+                 * to calibrate it's PWM sensitivity when it starts.
+                 */
+                twl_i2c_write_u8(TWL4030_MODULE_PWM0, MAX_VALUE,
+                                        TWL_PWM0_OFF);
+
+                /* first enable clock, then PWM0 out */
+                twl_i2c_read_u8(TWL4030_MODULE_INTBR, &r, TWL_INTBR_GPBR1);
+                r &= ~PWM0_ENABLE;
+                r |= PWM0_CLK_ENABLE;
+                twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);
+                r |= PWM0_ENABLE;
+                twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);
+
+                /*
+                 * TI made it very easy to enable digital control, so easy that
+                 * it often triggers unintentionally and disabes PWM control,
+                 * so wait until 1 wire mode detection window ends.
+                 */
+                usleep_range(2000, 10000);
+        }
+
+        twl_i2c_write_u8(TWL4030_MODULE_PWM0, MIN_VALUE + brightness,
+                                TWL_PWM0_OFF);
+
+done:
+        if (brightness != 0)
+                bl->props.state &= ~PANDORABL_WAS_OFF;
+        else
+                bl->props.state |= PANDORABL_WAS_OFF;
+
+        return 0;
+}
+
+static int pandora_backlight_get_brightness(struct backlight_device *bl)
+{
+        return bl->props.brightness;
+}
+
+static const struct backlight_ops pandora_backlight_ops = {
+        .options        = BL_CORE_SUSPENDRESUME,
+        .update_status  = pandora_backlight_update_status,
+        .get_brightness = pandora_backlight_get_brightness,
+};
+
+static int pandora_backlight_probe(struct platform_device *pdev)
+{
+        struct backlight_properties props;
+        struct backlight_device *bl;
+        u8 r;
+
+        memset(&props, 0, sizeof(props));
+        props.max_brightness = MAX_USER_VALUE;
+        props.type = BACKLIGHT_RAW;
+        bl = backlight_device_register(pdev->name, &pdev->dev,
+                        NULL, &pandora_backlight_ops, &props);
+        if (IS_ERR(bl)) {
+                dev_err(&pdev->dev, "failed to register backlight\n");
+                return PTR_ERR(bl);
+        }
+
+        platform_set_drvdata(pdev, bl);
+
+        /* 64 cycle period, ON position 0 */
+        twl_i2c_write_u8(TWL4030_MODULE_PWM0, 0x80, TWL_PWM0_ON);
+
+        bl->props.state |= PANDORABL_WAS_OFF;
+        bl->props.brightness = MAX_USER_VALUE;
+        backlight_update_status(bl);
+
+        /* enable PWM function in pin mux */
+        twl_i2c_read_u8(TWL4030_MODULE_INTBR, &r, TWL_INTBR_PMBR1);
+        r &= ~TWL_PMBR1_PWM0_MUXMASK;
+        r |= TWL_PMBR1_PWM0;
+        twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_PMBR1);
+
+        return 0;
+}
+
+static int pandora_backlight_remove(struct platform_device *pdev)
+{
+        struct backlight_device *bl = platform_get_drvdata(pdev);
+        backlight_device_unregister(bl);
+        return 0;
+}
+
+static struct platform_driver pandora_backlight_driver = {
+        .driver         = {
+                .name   = "pandora-backlight",
+                .owner  = THIS_MODULE,
+        },
+        .probe          = pandora_backlight_probe,
+        .remove         = pandora_backlight_remove,
+};
+
+module_platform_driver(pandora_backlight_driver);
+
+MODULE_AUTHOR("Gražvydas Ignotas <notasas@gmail.com>");
+MODULE_DESCRIPTION("Pandora Backlight Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:pandora-backlight");