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

[Ilias Apalodimas <ilias.apalodimas@linaro.org>]

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@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@linaro.org>
> > Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
> > Reviewed-by: Etienne Carriere <etienne.carriere@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.

Thanks
/Ilias

> 
> Regards,
> Simon