Hi Daren, Guido,
>From: Etheridge, Darren
>>On 06/26/2014 10:40 AM, Guido Martínez wrote:
>> 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 <pe...@ti.com>
>>> ---
>
><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?
>>
Yes, I'll check this one again at my end.
>>> + 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.
>>
I could run and test 'fbtest' and 'fbconsole' on this cape, using following
configs
CONFIG_DRM=y
CONFIG_DRM_TILCDC=y
[...]
CONFIG_FB=y
CONFIG_FIRMWARE_EDID=y
CONFIG_FRAMEBUFFER_CONSOLE=y
>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/
>
Yes, probably I got the pixel-clock timing wrong, I'll fix this.
It should be 9.2MHz as per
www.newhavendisplay.com/specs/NHD-4.3-480272MF-ATXI-T-1.pdf
Table: Electrical Characteristics
But as 'hsync' timings are relative to pixel-clock somehow it worked for me.
I got other vsync and hsync timings from following reference:
www.newhavendisplay.com/app_notes/OTA5180A.pdf
Table: 8.4.1 480XRGBX272 Vertical Timing
Table: 8.4.2 480XRGBX272 Horizontal Timing
And I/O signal polarity for vsync-active and hsync-active from
Table: 5. SIGNAL DESCRIPTIONS
with regards, pekon
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