Guido, Pekon,
On 06/26/2014 10:40 AM, Guido Martínez wrote:
Hi Pekon,
I had some issues with this patch. Booting linux-next on a BeagleBone
Black with this exact LCD left me with an unusable white screen. Please
see below for some details.
On Tue, Jun 24, 2014 at 05:54:26PM +0530, Pekon Gupta wrote:
This patch adds support for LCD4 cape as advertised on
http://elinux.org/CircuitCo:BeagleBone_LCD4
This cape has:
* 480x272 TFT-LCD panel
- LCD panel datasheet and timing information are sourced from [1]
- LCD backlight is connected to 'EHRPWM1A' on cape board, but its used for
enabling backlight power-supply. So 'gpio-backlight' driver is used instead
of 'pwm-backlight' driver (Kconfig: BACKLIGHT_GPIO=y).
* 4-wire resistive Touchscreen
*Known constrains*
As LCD panel pins (lcd_data, hsync, vsync, pclk) are shared with on-board
NXP HDMI framer, so either HDMI or LCD-cape can be used at time. Thus while
using this cape 'hdmi' DT node needs to be disabled in am335x-boneblack.dts
[1] www.newhavendisplay.com/specs/NHD-4.3-480272MF-ATXI-T-1.pdf
www.newhavendisplay.com/app_notes/OTA5180A.pdf
Signed-off-by: Pekon Gupta <pekon@xxxxxx>
---
<snip>
+
+ panel {
+ status = "disabled";
+ compatible = "ti,tilcdc,panel";
+ pinctrl-names = "default";
+ pinctrl-0 = <&bbcape_lcd_pins>;
+ panel-info {
+ ac-bias = <255>;
+ ac-bias-intrpt = <0>;
+ dma-burst-sz = <16>;
+ bpp = <16>;
+ fdd = <0x80>;
+ sync-edge = <0>;
+ sync-ctrl = <0>;
I had to set this to <1>. Does that make sense?
+ raster-order = <0>;
+ fifo-th = <0>;
+ };
+ display-timings {
+ native-mode = <&timing0>;
+ /* www.newhavendisplay.com/app_notes/OTA5180A.pdf */
+ timing0: 480x272 {
+ clock-frequency = <30000000>;
+ hactive = <480>;
+ vactive = <272>;
+ hfront-porch = <8>;
+ hback-porch = <47>;
+ hsync-len = <41>;
+ vback-porch = <2>;
+ vfront-porch = <3>;
+ vsync-len = <10>;
+ hsync-active = <0>;
+ vsync-active = <0>;
+ de-active = <1>;
+ pixelclk-active = <0>;
Are you sure these timings are ok? When enabling the sync control I get
an usable display, but it looks a bit funny. For example an all black
display looks very clear and has a dotted pattern.
I tried to take a picture of it but it doesn't show.
These timings look wrong to me, for instance this sets a clock frequency
of 30MHz where as the linked app-note says 9MHz. I think the LCD4 cape
uses the same LCD panel as is used on the AM335x EVMSK. Therefore the
display timings from my DT patch for the EVMSK should work:
https://patchwork.kernel.org/patch/4144801/
Darren
Also I'm just guessing about the timings, maybe it's something else?
+ };
+ };
+ };
+};
diff --git a/arch/arm/boot/dts/am335x-bone.dts b/arch/arm/boot/dts/am335x-bone.dts
index f16bfcf..41439dc 100644
--- a/arch/arm/boot/dts/am335x-bone.dts
+++ b/arch/arm/boot/dts/am335x-bone.dts
@@ -10,6 +10,7 @@
#include "am33xx.dtsi"
#include "am335x-bone-common.dtsi"
#include "am335x-bone-memory-cape.dts"
+#include "am335x-bone-display-cape.dts"
&ldo3_reg {
regulator-min-microvolt = <1800000>;
diff --git a/arch/arm/boot/dts/am335x-boneblack.dts b/arch/arm/boot/dts/am335x-boneblack.dts
index e6d7e54..03232c7 100644
--- a/arch/arm/boot/dts/am335x-boneblack.dts
+++ b/arch/arm/boot/dts/am335x-boneblack.dts
@@ -10,6 +10,7 @@
#include "am33xx.dtsi"
#include "am335x-bone-common.dtsi"
#include "am335x-bone-memory-cape.dts"
+#include "am335x-bone-display-cape.dts"
&ldo3_reg {
regulator-min-microvolt = <1800000>;
--
1.8.5.1.163.gd7aced9
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