[U-Boot] Issue enabling TPM 2.0 on RPI

[Miquel Raynal]

Hi Elena,

Elena Unix <elenaunix01 at gmail.com> wrote on Fri, 14 Jun 2019 09:43:46
+0200:

> Hello,
> 
> I am trying to enable the TPM 2.0 SLB9670 in U-Boot for a Raspberry Pi 3 B+. More precisely, the TPM is on an add-on board, the IRIDIUM SLB9670.
> The communication between the RPI and the TPM is ensured by SPI so I enabled the software spi driver (spi-gpio) in U-Boot because the bcm28x spi driver is not available in U-Boot.
> 
> CONFIG_SPI=y
> CONFIG_DM_SPI=y
> CONFIG_SOFT_SPI=y

Are you sure the SPI bus is correctly driven? Can you connect anything
else and ensure it works? You may also probe all the GPIO lines (using
an oscilloscope) and check each of them is clocked correctly.

> 
> Then, I enabled the TPM support in U-Boot.
> 
> CONFIG_CMD_TPM_V2=y
> CONFIG_CMD_TPM=y

If you use TPM V2, CMD_TPM is not needed. But that's not your problem.

> CONFIG_TPM_V2=y
> CONFIG_TPM2_TIS_SPI=y
> CONFIG_TPM=y

Looks fine.

> 
> Finally, I updated my Device Tree.
> /dts-v1/
> / {
> ...
>    aliases {
>        spi0 = &soft_spi;
>    };
> 
>    soft_spi: soft-spi {
>        compatible = "spi-gpio";
>        pinctrl-names = "default";
>        pinctrl-0 = <&spi0_gpio7>;
>        status = "okay";
>        gpio-sck = <&gpio 11 0>;
>        gpio-mosi = <&gpio 10 0>;
>        gpio-miso = <&gpio 9 0>;
>        cs-gpios = <&gpio 7 1>;
>        #address-cells = <1>;
>        #size-cells = <0>;
> 
>        slb9670: slb9670 at 0 {
>            compatible = "tis,tpm2-spi";
>            reg = <1>;
>            #address-cells = <1>;
>            #size-cells = <0>;
>            spi-max-frequency = <32000000>;

You might want to slow down a bit this frequency, try it with 1MHz,
just for testing (and see something meaningful with the scope).

>            status = "okay";
>        };
>    };
> 
>    spio0_gpio7: spio0_gpio7 {
>        brcm,pins = <7 8 9 10 11>;
>        brcm,function = <4>;

If you bit-bang the SPI bus, I suppose you must use the GPIO function
on each pin, is <4> the GPIO function or the SPI function?

>    };
> ...
> };
> 
> But, when I try to execute the following command : 
> U-Boot> tpm2 init
> 
> I have the following response :
> 
> tpm_tis_spi_probe : missing reset GPIO

This is indeed harmless, just a warning.

> tpm_tis_spi_request_locality : Timeout getting locality : -2

This usually means you cannot talk to the chip.

> tpm_tis_spi_probe : could not request locality 0
> Could not find TPM (ret=-2)
> 
> The Iridium board contains a reset circuit on board, which pulls the reset line of the TPM to GND after VCC becomes available, so the reset GPIO is not needed I think.
> 
> I don’t see what is wrong with my setup, a little help would be very appreciated.
> 
> Thank you in advance, 
> Elena
> ___________


Good luck,
Miquèl