video: mx3fb: Add backlight control support

This patch add backlight control support to allow dimming the backlight
using the internal PWM. Currently the brightness is set fixed to a
maximum of 255.

Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

2 files changed, 82 insertions, 0 deletions

diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig
index 96f0f42d53bc..59c98bfd5a8a 100644
--- a/drivers/video/fbdev/Kconfig
+++ b/drivers/video/fbdev/Kconfig
@@ -2336,6 +2336,7 @@ config FB_MX3
         select FB_CFB_FILLRECT
         select FB_CFB_COPYAREA
         select FB_CFB_IMAGEBLIT
+        select BACKLIGHT_CLASS_DEVICE
         default y
         help
           This is a framebuffer device for the i.MX31 LCD Controller. So
diff --git a/drivers/video/fbdev/mx3fb.c b/drivers/video/fbdev/mx3fb.c
index ee95de80a487..c645a0a0c341 100644
--- a/drivers/video/fbdev/mx3fb.c
+++ b/drivers/video/fbdev/mx3fb.c
@@ -27,6 +27,7 @@
 #include <linux/clk.h>
 #include <linux/mutex.h>
 #include <linux/dma/ipu-dma.h>
+#include <linux/backlight.h>
 
 #include <linux/platform_data/dma-imx.h>
 #include <linux/platform_data/video-mx3fb.h>
@@ -241,6 +242,7 @@ struct mx3fb_data {
         void __iomem            *reg_base;
         spinlock_t              lock;
         struct device           *dev;
+        struct backlight_device *bl;
 
         uint32_t                h_start_width;
         uint32_t                v_start_width;
@@ -271,6 +273,71 @@ struct mx3fb_info {
         struct fb_var_screeninfo        cur_var; /* current var info */
 };
 
+static void sdc_set_brightness(struct mx3fb_data *mx3fb, uint8_t value);
+static u32 sdc_get_brightness(struct mx3fb_data *mx3fb);
+
+static int mx3fb_bl_get_brightness(struct backlight_device *bl)
+{
+        struct mx3fb_data *fbd = bl_get_data(bl);
+
+        return sdc_get_brightness(fbd);
+}
+
+static int mx3fb_bl_update_status(struct backlight_device *bl)
+{
+        struct mx3fb_data *fbd = bl_get_data(bl);
+        int brightness = bl->props.brightness;
+
+        if (bl->props.power != FB_BLANK_UNBLANK)
+                brightness = 0;
+        if (bl->props.fb_blank != FB_BLANK_UNBLANK)
+                brightness = 0;
+
+        fbd->backlight_level = (fbd->backlight_level & ~0xFF) | brightness;
+
+        sdc_set_brightness(fbd, fbd->backlight_level);
+
+        return 0;
+}
+
+static const struct backlight_ops mx3fb_lcdc_bl_ops = {
+        .update_status = mx3fb_bl_update_status,
+        .get_brightness = mx3fb_bl_get_brightness,
+};
+
+static void mx3fb_init_backlight(struct mx3fb_data *fbd)
+{
+        struct backlight_properties props;
+        struct backlight_device *bl;
+
+        if (fbd->bl)
+                return;
+
+        memset(&props, 0, sizeof(struct backlight_properties));
+        props.max_brightness = 0xff;
+        props.type = BACKLIGHT_RAW;
+        sdc_set_brightness(fbd, fbd->backlight_level);
+
+        bl = backlight_device_register("mx3fb-bl", fbd->dev, fbd,
+                                       &mx3fb_lcdc_bl_ops, &props);
+        if (IS_ERR(bl)) {
+                dev_err(fbd->dev, "error %ld on backlight register\n",
+                                PTR_ERR(bl));
+                return;
+        }
+
+        fbd->bl = bl;
+        bl->props.power = FB_BLANK_UNBLANK;
+        bl->props.fb_blank = FB_BLANK_UNBLANK;
+        bl->props.brightness = mx3fb_bl_get_brightness(bl);
+}
+
+static void mx3fb_exit_backlight(struct mx3fb_data *fbd)
+{
+        if (fbd->bl)
+                backlight_device_unregister(fbd->bl);
+}
+
 static void mx3fb_dma_done(void *);
 
 /* Used fb-mode and bpp. Can be set on kernel command line, therefore file-static. */
@@ -628,6 +695,16 @@ static int sdc_set_global_alpha(struct mx3fb_data *mx3fb, bool enable, uint8_t a
         return 0;
 }
 
+static u32 sdc_get_brightness(struct mx3fb_data *mx3fb)
+{
+        u32 brightness;
+
+        brightness = mx3fb_read_reg(mx3fb, SDC_PWM_CTRL);
+        brightness = (brightness >> 16) & 0xFF;
+
+        return brightness;
+}
+
 static void sdc_set_brightness(struct mx3fb_data *mx3fb, uint8_t value)
 {
         dev_dbg(mx3fb->dev, "%s: value = %d\n", __func__, value);
@@ -1534,6 +1611,8 @@ static int mx3fb_probe(struct platform_device *pdev)
         if (ret < 0)
                 goto eisdc0;
 
+        mx3fb_init_backlight(mx3fb);
+
         return 0;
 
 eisdc0:
@@ -1556,6 +1635,8 @@ static int mx3fb_remove(struct platform_device *dev)
         chan = &mx3_fbi->idmac_channel->dma_chan;
         release_fbi(fbi);
 
+        mx3fb_exit_backlight(mx3fb);
+
         dma_release_channel(chan);
         dmaengine_put();