[PATCH v2 08/10] tpm: Add the RNG child device

[Sughosh Ganu]

hi Simon,

On Tue, 1 Mar 2022 at 20:29, Simon Glass <sjg at chromium.org> wrote:
>
> Hi Sughosh,
>
> On Mon, 28 Feb 2022 at 05:07, Sughosh Ganu <sughosh.ganu at linaro.org> 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>
> > ---
> >
> > Changes since V1: None
> >
> >  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 should be in the Makefile so that we only build this file if TPM
> is enabled.

The Makefile allows for the tpm uclass driver to be built for SPL and
TPL stages as well. The addition of the RNG device is to be done only
in the u-boot proper stage, since we enable RNG support only in u-boot
proper. Thanks.

-sughosh

>
> > +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),
> >  };
> > --
> > 2.25.1
> >
>
> Regards,
> Simon