[PATCH v3] video: mx3fb: Add backlight control support

[PATCH v3] video: mx3fb: Add backlight control support

[Alexander Stein]

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>
---
Changes in v3:
* Add a more descriptive commit message

Changes in v2:
* rebased to v3.15-rc4

 drivers/video/fbdev/mx3fb.c | 98 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 98 insertions(+)

diff --git a/drivers/video/fbdev/mx3fb.c b/drivers/video/fbdev/mx3fb.c
index 142e860..10a7244 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>
@@ -34,6 +35,12 @@
 #include <asm/io.h>
 #include <asm/uaccess.h>
 
+#if defined(CONFIG_BACKLIGHT_CLASS_DEVICE) || \
+	(defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE) && \
+		defined(CONFIG_MX3FB_MODULE))
+#define PWM_BACKLIGHT_AVAILABLE
+#endif
+
 #define MX3FB_NAME		"mx3_sdc_fb"
 
 #define MX3FB_REG_OFFSET	0xB4
@@ -242,6 +249,10 @@ struct mx3fb_data {
 	spinlock_t		lock;
 	struct device		*dev;
 
+#ifdef PWM_BACKLIGHT_AVAILABLE
+	struct backlight_device	*bl;
+#endif
+
 	uint32_t		h_start_width;
 	uint32_t		v_start_width;
 	enum disp_data_mapping	disp_data_fmt;
@@ -271,6 +282,74 @@ struct mx3fb_info {
 	struct fb_var_screeninfo	cur_var; /* current var info */
 };
 
+static void sdc_set_brightness(struct mx3fb_data *mx3fb, uint8_t value);
+
+#ifdef PWM_BACKLIGHT_AVAILABLE
+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);
+}
+#endif
+
 static void mx3fb_dma_done(void *);
 
 /* Used fb-mode and bpp. Can be set on kernel command line, therefore file-static. */
@@ -628,6 +707,18 @@ static int sdc_set_global_alpha(struct mx3fb_data *mx3fb, bool enable, uint8_t a
 	return 0;
 }
 
+#ifdef PWM_BACKLIGHT_AVAILABLE
+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;
+}
+#endif
+
 static void sdc_set_brightness(struct mx3fb_data *mx3fb, uint8_t value)
 {
 	dev_dbg(mx3fb->dev, "%s: value = %d\n", __func__, value);
@@ -1534,6 +1625,9 @@ static int mx3fb_probe(struct platform_device *pdev)
 	if (ret < 0)
 		goto eisdc0;
 
+#ifdef PWM_BACKLIGHT_AVAILABLE
+	mx3fb_init_backlight(mx3fb);
+#endif
 	return 0;
 
 eisdc0:
@@ -1557,6 +1651,10 @@ static int mx3fb_remove(struct platform_device *dev)
 	chan = &mx3_fbi->idmac_channel->dma_chan;
 	release_fbi(fbi);
 
+#ifdef PWM_BACKLIGHT_AVAILABLE
+	mx3fb_exit_backlight(mx3fb);
+#endif
+
 	dma_release_channel(chan);
 	dmaengine_put();
 
-- 
1.8.5.5

Re: [PATCH v3] video: mx3fb: Add backlight control support

[Tomi Valkeinen]

[-- Attachment #1: Type: text/plain, Size: 1460 bytes --]

On 08/05/14 17:38, Alexander Stein wrote:
> 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>
> ---
> Changes in v3:
> * Add a more descriptive commit message
> 
> Changes in v2:
> * rebased to v3.15-rc4
> 
>  drivers/video/fbdev/mx3fb.c | 98 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 98 insertions(+)
> 
> diff --git a/drivers/video/fbdev/mx3fb.c b/drivers/video/fbdev/mx3fb.c
> index 142e860..10a7244 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>
> @@ -34,6 +35,12 @@
>  #include <asm/io.h>
>  #include <asm/uaccess.h>
>  
> +#if defined(CONFIG_BACKLIGHT_CLASS_DEVICE) || \
> +	(defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE) && \
> +		defined(CONFIG_MX3FB_MODULE))
> +#define PWM_BACKLIGHT_AVAILABLE
> +#endif

I'm not very fond of this kind of ifdeffery. It makes the driver rather
messy and confusing, especially if large blocks of code are inside the
ifdefs.

Can't you just make the driver select BACKLIGHT_CLASS_DEVICE?

 Tomi



[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 819 bytes --]

Re: [PATCH v3] video: mx3fb: Add backlight control support

[Alexander Stein]

On Friday 09 May 2014 12:11:29, Tomi Valkeinen wrote:
> On 08/05/14 17:38, Alexander Stein wrote:
> > 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>
> > ---
> > Changes in v3:
> > * Add a more descriptive commit message
> > 
> > Changes in v2:
> > * rebased to v3.15-rc4
> > 
> >  drivers/video/fbdev/mx3fb.c | 98 +++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 98 insertions(+)
> > 
> > diff --git a/drivers/video/fbdev/mx3fb.c b/drivers/video/fbdev/mx3fb.c
> > index 142e860..10a7244 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>
> > @@ -34,6 +35,12 @@
> >  #include <asm/io.h>
> >  #include <asm/uaccess.h>
> >  
> > +#if defined(CONFIG_BACKLIGHT_CLASS_DEVICE) || \
> > +	(defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE) && \
> > +		defined(CONFIG_MX3FB_MODULE))
> > +#define PWM_BACKLIGHT_AVAILABLE
> > +#endif
> 
> I'm not very fond of this kind of ifdeffery. It makes the driver rather
> messy and confusing, especially if large blocks of code are inside the
> ifdefs.
> 
> Can't you just make the driver select BACKLIGHT_CLASS_DEVICE?

Well, sure I can. I just went the same way as atmel_lcdfb.c did. Will sent new patch.

Regards,
Alexander
-- 
Dipl.-Inf. Alexander Stein

SYS TEC electronic GmbH
Am Windrad 2
08468 Heinsdorfergrund
Tel.: 03765 38600-1156
Fax: 03765 38600-4100
Email: alexander.stein@systec-electronic.com
Website: www.systec-electronic.com
 
Managing Director: Dipl.-Phys. Siegmar Schmidt
Commercial registry: Amtsgericht Chemnitz, HRB 28082