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

Etienne Carriere
2022-08-26T09:07:46Z

Hello Ilias, Jens,

On Fri, 26 Aug 2022 at 10:46, Jens Wiklander <jens.wiklander@linaro.org> wrote:
>
> On Tue, Aug 23, 2022 at 10:11 AM 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.
> >
> > Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
> > ---
> > drivers/tee/optee/core.c | 22 +++++++++++++++++++---
> > 1 file changed, 19 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/tee/optee/core.c b/drivers/tee/optee/core.c
> > index a89d62aaf0b3..48a9b59171cb 100644
> > --- a/drivers/tee/optee/core.c
> > +++ b/drivers/tee/optee/core.c
> > @@ -31,6 +31,20 @@ 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
> > + { "optee-rng", "optee-rng" },
> > +#endif
> > +#ifdef CONFIG_TPM2_FTPM_TEE
> > + { "ftpm-tee", "ftpm-tee" },
> > +#endif
> > +};
> > +
> > +#define MAX_TEE_BUS_DEV_COUNT ARRAY_SIZE(optee_bus_probe)
> > +
> > struct rpc_param {
> > u32 a0;
> > u32 a1;
> > @@ -643,7 +657,7 @@ 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");
> > @@ -672,8 +686,10 @@ 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 < MAX_TEE_BUS_DEV_COUNT; i++) {

I would use ARRAY_SIZE(optee_bus_probe) straight here. Macro
indirection is not really useful imho.

> > + ret = device_bind_driver(dev, optee_bus_probe[i].drv_name,
> > + optee_bus_probe[i].dev_name, &child);
> > if (ret)
> > return ret;
>
> I wonder which behaviour is most useful. Disable OP-TEE support
> completely if there's some error when binding dependent drivers or to
> just complain a bit but continue.

I agree with you, this should better print the status and proceed with
the next driver.
There are other occurrences of such behaviour in U-Boot.

Br,
etienne

>
> Cheers,
> Jens
>
>
> >
> > }
> > --
> > 2.34.1
> >