General MIPI DSI questions

Autonomous Machines Jetson & Embedded Systems Jetson TX1
1

Hi!,

This is the first time I’m working with MIPI DSI so please forgive what may be “stupid” questions.
I would like to enable two display’s on the TX1, one is the normal HDMI via a standard HDMI connector and the other is this below full HD MIPI DSI panel:

My first question is: Does TX “L4T v.24” support dual display with HDMI and DSI panel?

The second question is if I have done the pin out correctly below as I’m guessing DSI0 and DSI1 can be combined to 4-lane?

JETSON DISPLAY PANEL:
G34 DSI0_CLK- → DSI_CLK- on panel
G33 DSI0_CLK+ → DSI_CLK+
F35 DSI0_D0- → DSI_D0-
F34 DSI0_D0+ → DSI_D0+
H33 DSI0_D1- → DSI_D1-
H32 DSI0_D1+ → DSI_D1+
C35 DSI1_D0- → DSI_D2-
C34 DSI1_D0+ → DSI_D2+
E33 DSI1_D1- → DSI_D3-
E32 DSI1_D1+ → DSI_D3+
A25 LCD_TE → (TE) TEARING OUTPUT
LCD_VDD_EN → RESET

I’m a bit at a loss in regards to the LCD’s pin called “LEDPWM” because in section 7-2 page 10 they describe that LED+/- are just that (LED’s in series with no attach to a driver) so I’m guessingthat LEDPWM is an output from the panel to control an external LED driver and since I would rather use the JETSON LCD0_BKLT_PWM output my plan was to totally omit the lcd LEDPWM signal and use a LED driver controlled from jetson instead.

On page 14 there’s a table of commands that needs to be send to the LCD after power on there’s two different DSI data types (Generic and DCS) where exactly in the Jetson do I put these commands??

on Page 15 there’s likewise two commands that needs to be executed during power off of the panel - where would I insert these?

On other displays i have worked with you had to specify a pixel clock, sync signals, porch etc… does MIPI somehow by magic auto detect this information from the LCD (much like EDID on HDMI)? - I ask because the datasheet doesn’t mention anything at all

Is there any problems in setting the Jetson DSI0/1 to work with this 1080p60 panel?

Would it be possible to connect a DSI to HDMI bridge chip to the DSI2/3 port and mirrorthe image of either the normal native jetson HDMI port or the DSI0/1 LCD panel? (I don’t need 3 individual LCD’s but rather 2 different outputs and a third mirrored one if possible)

Thanks
Lasse

2

Hi Lasse,

Tx1 supports HDMI+DSI display and HDMI is default enabled.

As for the third-part DSI panel, it needs vendor to give you hw design and sw driver programming guide.

3

LasseRoedtnes,

My first question is: Does TX “L4T v.24” support dual display with HDMI and DSI panel?
Yes, we support dual display (HDMI+DSI). You can refer to p2371-2180.conf and see what DTB_FILE it is using. That DTB file has enabled DSI panel in it.

The second question is if I have done the pin out correctly below as I’m guessing DSI0 and DSI1 can be combined to 4-lane?
Yes, it should work.

[b]You could refer to some of our existing dts. Please download our kernel source from the website.

If you are still in r24, the files should be under

dts → ./arch/arm/boot/dts/
driver → ./arch/arm64/mach-tegra/

Those dtsi with name “s” in second field is for Sharp panel. For example, panel-s-wuxga-8-0.dtsi is for a wuxga 8" Sharp panel.[/b]

On page 14 there’s a table of commands that needs to be send to the LCD after power on there’s two different DSI data types (Generic and DCS) where exactly in the Jetson do I put these commands??
It sounds like the init command, please refer to the existing dts for this.

On other displays i have worked with you had to specify a pixel clock, sync signals, porch etc… does MIPI somehow by magic auto detect this information from the LCD (much like EDID on HDMI)? - I ask because the datasheet doesn’t mention anything at all

Our dsi driver does not read EDID from panel. Instead, it directly reads modes from the dts.

Would it be possible to connect a DSI to HDMI bridge chip to the DSI2/3 port and mirrorthe image of either the normal native jetson HDMI port or the DSI0/1 LCD panel? (I don’t need 3 individual LCD’s but rather 2 different outputs and a third mirrored one if possible)

For this usecase, I am sorry to say that this is not in our driver’s support. Some forum users had tried this before and failed. Since tegra only has 2 display controllers(dc), it cannot performance 3 head display as tx2. To use up to 3 heads, you must enable dsi ganged mode. However, our driver does not support ganged mode.