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

[Sughosh Ganu]

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.

-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),
> >   };
>