[U-Boot] [PATCH 01/21] drivers/video/am335x-fb: Add possibility to wait for stable power/picture

Hannes Petermaier
2015-01-30T13:25:04Z

Often on boards exists a circuit which switches power on/off to LCD display.
Due to the need of limiting the in-rush current the output voltage from this
circuit rises "slowly", so it is necessary to wait a bit (VCC ramp up time)
before starting output on LCD-pins.
This time is specified in <n> ms within the panel-settings, called "pup_delay"

Further some LCDs need a couple of frames to stabilize the image on it.
We have now the possibility to wait some time after starting output on LCD.
This time is also specified in <n> ms within panel-settings, called "pon_delay"

Signed-off-by: Hannes Petermaier <oe5hpm@oevsv.at>
---
drivers/video/am335x-fb.c | 13 ++++++++-----
drivers/video/am335x-fb.h | 9 +++++++--
2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/drivers/video/am335x-fb.c b/drivers/video/am335x-fb.c
index ab98941..6f95649 100644
--- a/drivers/video/am335x-fb.c
+++ b/drivers/video/am335x-fb.c
@@ -127,6 +127,12 @@ int am335xfb_init(struct am335x_lcdpanel *panel)
memset((void *)gd->fb_base, 0, 0x20);
*(unsigned int *)gd->fb_base = 0x4000;

+ /* turn ON display through powercontrol function if accessible */
+ if (0 != panel->panel_power_ctrl)
+ panel->panel_power_ctrl(1);
+
+ debug("am335x-fb: wait for stable power ...\n");
+ mdelay(panel->pup_delay);
lcdhw->clkc_enable = LCD_CORECLKEN | LCD_LIDDCLKEN | LCD_DMACLKEN;
lcdhw->raster_ctrl = 0;
lcdhw->ctrl = LCD_CLK_DIVISOR(panel->pxl_clk_div) | LCD_RASTER_MODE;
@@ -159,11 +165,8 @@ int am335xfb_init(struct am335x_lcdpanel *panel)

gd->fb_base += 0x20; /* point fb behind palette */

- /* turn ON display through powercontrol function if accessible */
- if (0 != panel->panel_power_ctrl) {
- mdelay(panel->pon_delay);
- panel->panel_power_ctrl(1);
- }
+ debug("am335x-fb: waiting picture to be stable.\n.");
+ mdelay(panel->pon_delay);

return 0;
}
diff --git a/drivers/video/am335x-fb.h b/drivers/video/am335x-fb.h
index 8a0b131..7f799d1 100644
--- a/drivers/video/am335x-fb.h
+++ b/drivers/video/am335x-fb.h
@@ -55,9 +55,14 @@ struct am335x_lcdpanel {
unsigned int vsw; /* Vertical Sync Pulse Width */
unsigned int pxl_clk_div; /* Pixel clock divider*/
unsigned int pol; /* polarity of sync, clock signals */
+ unsigned int pup_delay; /*
+ * time in ms after power on to
+ * initialization of lcd-controller
+ * (VCC ramp up time)
+ */
unsigned int pon_delay; /*
- * time in ms for turning on lcd after
- * initializing lcd-controller
+ * time in ms after initialization of
+ * lcd-controller (pic stabilization)
*/
void (*panel_power_ctrl)(int); /* fp for power on/off display */
};
--
1.7.9.5