GPIO6 on Apalis TK1 hooked to 2 outputs

Technical Support
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1

Hi
We use GPIO6 as an output ( Address 238) .
in Apalis spec you specify that GPIO6 is connected to 2 outputs and suggest to disable (put to High Z) the not used output ( OWR) .
Please describe how to do it ?
Thanks
Oded

2

Assuming you are talking about downstream this may be done by simply tri-stating the other pin e.g. as can be seen here.

The exact same thing may be found in mainline e.g. here.

3

Thanks Marcel,

Are the below values default values ?
Does a change means recompiling the Kernel ?
The issue with this GPIO 6 ( Address 238) that @ power up for some time the
voltage measured is ~2V ( not 0V , not 3.3V) and I wonder why …
Any idea ?

sdmmc3_clk_lb_in_pee5 { /* D6 GPIO */
				nvidia,pins = "sdmmc3_clk_lb_in_pee5";
				nvidia,function = "rsvd2";
				nvidia,pull = <TEGRA_PIN_PULL_NONE>;
				nvidia,tristate = <TEGRA_PIN_DISABLE>;
				nvidia,enable-input = <TEGRA_PIN_ENABLE>;
4

Are the below values default values ?

My understanding was that you are talking about Apalis GPIO6. However, sdmmc3_clk_lb_in_pee5 is the Apalis MMC1 D6 pin which due to only 4-bit slots being available may also be used as a GPIO. It really has nothing to do with Apalis GPIO6 at all. What you rather may be looking for is pex_l1_clkreq_n_pdd6 resp. owr the later being tri-stated by default.

Does a change means recompiling the Kernel ?

No, usually that may be changed in the device tree so simply re-compiling the device tree is sufficient.

The issue with this GPIO 6 ( Address 238) that @ power up for some time the voltage measured is ~2V ( not 0V , not 3.3V) and I wonder why … Any idea ?

The exact amount in “for some time” may be interesting as it could be either chip default, boot ROM default, U-Boot default and last but not least Linux kernel default. Unfortunately, the first two are outside any of our control but the later two may be customised.

5

Thanks Marcel,

  1. Yes , I meant Apalis GPIO6
  2. How can I set it to be “0” ( 0V) @ power up (U-Boot or Linux kernel default)
  3. If I set it to output only will it help ?

Please advise
Thanks
oded

6

Thanks marcel,

You are very welcome.

  1. Yes , I meant Apalis GPIO6

OK.

  1. How can I set it to be “0” ( 0V) @ power up (U-Boot or Linux kernel default)

U-Boot: Add GPIO_INIT(DD, 6, OUT0), here.

Linux kernel: Move the following line to below gpio-output-low here.

  1. If I set it to output only will it help ?

There is no such thing as output only. An output always needs to be either zero or one. Only inputs may be floating aka undefined.