[PATCH 08/10] tpm: Add the RNG child device

[Heinrich Schuchardt]

On 2/25/22 06:45, Sughosh Ganu wrote:
> On Fri, 25 Feb 2022 at 00:21, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>>
>> On 2/24/22 19:05, Sughosh Ganu wrote:
>>> The TPM device comes with the random number generator(RNG)
>>> functionality which is built into the TPM device. Add logic to add the
>>> RNG child device in the TPM uclass post probe callback.
>>>
>>> The RNG device can then be used to pass a set of random bytes to the
>>> linux kernel, need for address space randomisation through the
>>> EFI_RNG_PROTOCOL interface.
>>>
>>> Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
>>> ---
>>>    drivers/tpm/tpm-uclass.c | 58 +++++++++++++++++++++++++++++++++++++---
>>>    1 file changed, 54 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/tpm/tpm-uclass.c b/drivers/tpm/tpm-uclass.c
>>> index 8619da89d8..383cc7bc48 100644
>>> --- a/drivers/tpm/tpm-uclass.c
>>> +++ b/drivers/tpm/tpm-uclass.c
>>> @@ -16,6 +16,11 @@
>>>    #include <tpm-v2.h>
>>>    #include "tpm_internal.h"
>>>
>>> +#include <dm/lists.h>
>>> +
>>> +#define TPM_RNG1_DRV_NAME    "tpm1-rng"
>>> +#define TPM_RNG2_DRV_NAME    "tpm2-rng"
>>> +
>>>    bool is_tpm1(struct udevice *dev)
>>>    {
>>>        return IS_ENABLED(CONFIG_TPM_V1) && tpm_get_version(dev) == TPM_V1;
>>> @@ -147,12 +152,57 @@ int tpm_xfer(struct udevice *dev, const uint8_t *sendbuf, size_t send_size,
>>>        return 0;
>>>    }
>>>
>>> +#if IS_ENABLED(CONFIG_TPM)
>>
>> This is is superfluous.
>> This file is only compiled if CONFIG_$(SPL_TPL_)TPM = y.
>
> Yes, but I want the RNG child device addition to be done only in case
> of u-boot proper, not for SPL and TPM. We do not have RNG support for
> the SPL/TPM boot stages. So unless someone needs to enable RNG support
> for SPL/TPL stages, which I doubt, this code should run only in u-boot
> proper. Thanks.

The tpm-uclass.c is never compiled in SPL or TPL. Have a look at
drivers/tpm/Kconfig. There is no CONFIG_SPL_TPM or CONFIG_TPL_TPM symbol.

Best regards

Heinrich

>
> -sughosh
>
>>
>> Best regards
>>
>> Heinrich
>>
>>> +static int tpm_uclass_post_probe(struct udevice *dev)
>>> +{
>>> +     int ret;
>>> +     const char *drv = is_tpm1(dev) ? TPM_RNG1_DRV_NAME : TPM_RNG2_DRV_NAME;
>>> +     struct udevice *child;
>>> +
>>> +     ret = device_bind_driver(dev, drv, "tpm-rng0", &child);
>>> +     if (ret == -ENOENT) {
>>> +             log_err("No driver configured for tpm-rng device\n");
>>> +             return 0;
>>> +     }
>>> +
>>> +     if (ret) {
>>> +             log_err("Unable to bind rng driver with the tpm-rng device\n");
>>> +             return ret;
>>> +     }
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static int tpm_uclass_child_pre_probe(struct udevice *dev)
>>> +{
>>> +     int ret;
>>> +
>>> +     ret = tpm_open(dev->parent);
>>> +     if (ret == -EBUSY) {
>>> +             log_info("TPM device already opened\n");
>>> +     } else if (ret) {
>>> +             log_err("Unable to open TPM device\n");
>>> +             return ret;
>>> +     }
>>> +
>>> +     ret = tpm_startup(dev->parent, TPM_ST_CLEAR);
>>> +     if (ret)
>>> +             log_err("Unable to start TPM device\n");
>>> +
>>> +     return ret;
>>> +}
>>> +#endif /* CONFIG_TPM */
>>> +
>>>    UCLASS_DRIVER(tpm) = {
>>> -     .id             = UCLASS_TPM,
>>> -     .name           = "tpm",
>>> -     .flags          = DM_UC_FLAG_SEQ_ALIAS,
>>> +     .id                     = UCLASS_TPM,
>>> +     .name                   = "tpm",
>>> +     .flags                  = DM_UC_FLAG_SEQ_ALIAS,
>>>    #if CONFIG_IS_ENABLED(OF_REAL)
>>> -     .post_bind      = dm_scan_fdt_dev,
>>> +     .post_bind              = dm_scan_fdt_dev,
>>> +#endif
>>> +#if IS_ENABLED(CONFIG_TPM)
>>> +     .post_probe             = tpm_uclass_post_probe,
>>> +     .child_pre_probe        = tpm_uclass_child_pre_probe,
>>>    #endif
>>>        .per_device_auto        = sizeof(struct tpm_chip_priv),
>>>    };
>>