[U-Boot] Issue enabling TPM 2.0 on RPI

[Elena Unix]

Hi Miquèl,

Thank you for your answer.

> Miquel Raynal <miquel.raynal at bootlin.com> wrote on Mon, 17 Jun 2019 10:44:52 +0200:
> 
> 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.

I simply checked by doing a loopback test, i.e connecting MISO and MOSI by a cable and it worked.
I will test with an oscilloscope when I have one and keep you up to date.

> 
>> 
>> 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).

I tried to lower the frequency to 1MHZ but without success.

>>           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?

No the <4> function is the SPI function, thank you it was a mistake. I changed it to GPIO function but I have the same errors when executing tpm2 commands in U-Boot.

> 
>>   };
>> ...
>> };
>> 
>> 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

Moreover, I commented out the tpm_tis_spi_request_locality() function in the TPM driver just to perform a test by executing the U-Boot> tpm2 init
I then had the following response :
tpm_tis_spi_probe() SPI TPMv2.0 found (vid:15d1, did:001b, rid:10)

The identifiers are good so the communication with the TPM seems almost working ?

Thank you again,
Elena