Sysfs entires dpaux_dpcd and dpaux_i2c

Hi Team,

Can you please help to understand about the sysfs directories dpaux_dpcd and dpaux_i2c?

These directories contain the following sysfs entries.
addr data num_bytes
May I know how to use this features? @WayneWWW @JerryChang

Thanks,
Sakthi

hello sakthikrishna.b,

you may also refer to below kernel sources for debugfs creation.
for example,
$L4T_Sources/r32.5/Linux_for_Tegra/source/public/kernel/nvidia/drivers/video/tegra/dc/dp.c

it’s created for user-space to access to read/write dpcd registers.
for example,
sample of the read usage,

cd /sys/kernel/debug/tegra_dp[n]/dpaux_dpcd
echo 0x300 > addr
echo 4 > num_bytes
cat data
00 04 4b 00

sample of the write usage,

cd /sys/kernel/debug/tegra_dp[n]/dpaux_dpcd
echo 0x300 > addr
echo 4 > num_bytes
echo 00 04 4e 00 > data
cat data
00 04 4e 00

Hi @JerryChang,

Thank you for the reply.

  1. Could you please let me know where DPCD register names and address are defined? Is there any documentation for it?
  2. Is it possible to read/write DC_DISP_SD_BL_CONTROL register which is defined in kernel/nvidia/drivers/video/tegra/dc/dc_reg.h through the dpcd_aux sysfs entry?

Thanks,
Sakthi

Please refer to the Jetson TRM from our dlc.

Hi @WayneWWW and @JerryChang ,

I went through the TRM for the Xavier series. I didn’t get any register which is similar to DC_DISP_SD_BL_CONTROL ( defined in kernel/nvidia/drivers/video/tegra/dc/dc_reg.h).

May I know the procedure to write to this register?

Thanks,
Sakthi

hello sakthikrishna.b,

is your request to control brightness in the DP, by read/write dpcd registers?
if yes, it is not supported, according to Controlling brightness in DP - #14 by WayneWWW.
thanks

Hi @JerryChang ,

Is it possible to enable it some how by making changes in the driver? Could you please give some pointers regarding that?

Thanks,
Sakthi

hello sakthikrishna.b,

it is checked in the other thread, and it is not supported.