[PATCH v4] tee: optee: rework TA bus scanning code

[Simon Glass]

Hi Ilias,

On Tue, 6 Sept 2022 at 15:23, Ilias Apalodimas
<ilias.apalodimas at linaro.org> wrote:
>
> Hi Simon,
>
> On Tue, Sep 06, 2022 at 03:18:28PM -0600, Simon Glass wrote:
> > Hi,
> >
> > On Tue, 6 Sept 2022 at 03:37, Ilias Apalodimas
> > <ilias.apalodimas at linaro.org> wrote:
> > >
> > > Late versions of OP-TEE support a pseudo bus.  TAs that behave as
> > > hardware blocks (e.g TPM, RNG etc) present themselves on a bus which we can
> > > scan.  Unfortunately U-Boot doesn't support that yet. It's worth noting
> > > that we already have a workaround for RNG.  The details are in
> > > commit 70812bb83da6 ("tee: optee: bind rng optee driver")
> > >
> > > So let's add a list of devices based on U-Boot Kconfig options that we will
> > > scan until we properly implement the tee-bus functionality.
> > >
> > > While at it change the behaviour of the tee core itself wrt to device
> > > binding.  If some device binding fails, print a warning instead of
> > > disabling OP-TEE.
> > >
> > > Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> > > Reviewed-by: Jens Wiklander <jens.wiklander at linaro.org>
> > > Reviewed-by: Etienne Carriere <etienne.carriere at linaro.org>
> > > ---
> > > Changes since v3:
> > > - Use NULL instead of a child ptr on device_bind_driver(), since it's not
> > > really needed
> > > - Changed the style of the optee_bus_probe[] definition to
> > >   {.drv_name = xxx, .dev_name = yyy }
> > >
> > > Changes since v2:
> > > - Fixed typo on driver name ftpm-tee -> ftpm_tee
> > >
> > > Changes since v1:
> > > - remove a macro and use ARRAY_SIZE directly
> > >  drivers/tee/optee/core.c | 24 +++++++++++++++++++-----
> > >  1 file changed, 19 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/tee/optee/core.c b/drivers/tee/optee/core.c
> > > index a89d62aaf0b3..c201a4635e6b 100644
> > > --- a/drivers/tee/optee/core.c
> > > +++ b/drivers/tee/optee/core.c
> > > @@ -31,6 +31,18 @@ struct optee_pdata {
> > >         optee_invoke_fn *invoke_fn;
> > >  };
> > >
> > > +static const struct {
> > > +       const char *drv_name;
> > > +       const char *dev_name;
> > > +} optee_bus_probe[] = {
> > > +#ifdef CONFIG_RNG_OPTEE
> > > +       { .drv_name = "optee-rng", .dev_name = "optee-rng" },
> > > +#endif
> > > +#ifdef CONFIG_TPM2_FTPM_TEE
> > > +       { .drv_name = "ftpm_tee", .dev_name = "ftpm_tee" },
> > > +#endif
> > > +};
> > > +
> > >  struct rpc_param {
> > >         u32     a0;
> > >         u32     a1;
> > > @@ -642,8 +654,7 @@ static int optee_probe(struct udevice *dev)
> > >  {
> > >         struct optee_pdata *pdata = dev_get_plat(dev);
> > >         u32 sec_caps;
> > > -       struct udevice *child;
> > > -       int ret;
> > > +       int ret, i;
> > >
> > >         if (!is_optee_api(pdata->invoke_fn)) {
> > >                 dev_err(dev, "OP-TEE api uid mismatch\n");
> > > @@ -672,10 +683,13 @@ static int optee_probe(struct udevice *dev)
> > >          * in U-Boot, the discovery of TA on the TEE bus is not supported:
> > >          * only bind the drivers associated to the supported OP-TEE TA
> > >          */
> > > -       if (IS_ENABLED(CONFIG_RNG_OPTEE)) {
> > > -               ret = device_bind_driver(dev, "optee-rng", "optee-rng", &child);
> > > +
> > > +       for (i = 0; i < ARRAY_SIZE(optee_bus_probe); i++) {
> > > +               ret = device_bind_driver(dev, optee_bus_probe[i].drv_name,
> > > +                                        optee_bus_probe[i].dev_name, NULL);
> > >                 if (ret)
> > > -                       return ret;
> > > +                       dev_warn(dev, "Failed to bind device %s\n",
> > > +                                optee_bus_probe[i].dev_name);
> >
> > Please add device tree nodes for these and all this code can go away.
>
> That's the exact opposite of what the commit message describes.  OP-TEE
> supports a scannable bus ifor TAs that  behave like hardware blocks and
> doesn't need a DT entry.  Since it's really the TAs compilation decision
> to support that or not having them as a DT node is not always the right
> choice.

This is continuing the perversion of how things are supposed to work
in driver model.

We need to talk about this because it is simply the wrong way to be
approaching this. There is nothing wrong with putting things in the DT
and this is how U-Boot works. For now, please create a binding and get
it reviewed. You don't need all the internal objects but you do need
an OP-TEE driver and node, as we have with PCI.

Regards,
Simon