Re: [PATCH v2 10/18] firmware: qcom_scm-64: Improve SMC convention detection

[eberman]

On 2019-11-15 16:21, Stephen Boyd wrote:
> Quoting Elliot Berman (2019-11-12 13:22:46)
> > diff --git a/drivers/firmware/qcom_scm-64.c 
> > b/drivers/firmware/qcom_scm-64.c
> > index 977654bb..b82b450 100644
> > --- a/drivers/firmware/qcom_scm-64.c
> > +++ b/drivers/firmware/qcom_scm-64.c
> > @@ -302,21 +302,20 @@ int __qcom_scm_hdcp_req(struct device *dev, 
> > struct qcom_scm_hdcp_req *req,
> >
> >  void __qcom_scm_init(void)
> >  {
> > -       u64 cmd;
> > -       struct arm_smccc_res res;
> > -       u32 function = SMCCC_FUNCNUM(QCOM_SCM_SVC_INFO, 
> > QCOM_SCM_INFO_IS_CALL_AVAIL);
> > -
> > -       /* First try a SMC64 call */
> > -       cmd = ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, 
> > ARM_SMCCC_SMC_64,
> > -                                ARM_SMCCC_OWNER_SIP, function);
> > -
> > -       arm_smccc_smc(cmd, QCOM_SCM_ARGS(1), cmd & 
> > (~BIT(ARM_SMCCC_TYPE_SHIFT)),
> > -                     0, 0, 0, 0, 0, &res);
> > -
> > -       if (!res.a0 && res.a1)
> > -               qcom_smccc_convention = ARM_SMCCC_SMC_64;
> > -       else
> > -               qcom_smccc_convention = ARM_SMCCC_SMC_32;
> > +       qcom_smccc_convention = ARM_SMCCC_SMC_64;
> > +       if (__qcom_scm_is_call_available(NULL, QCOM_SCM_SVC_INFO,
> > +                       QCOM_SCM_INFO_IS_CALL_AVAIL) == 1)
>
> Is this asking if the "is call available function" is available by 
> using
> the is call available function? That is recursive. Isn't that why we
> make a manually open coded SMC call to see if it works? If this isn't
> going to work we may want to just have a property in DT that tells us
> what to do.

Yes. The reason the open coded SMC call was made was because a fast call
works better here. __qcom_scm_is_call_available uses standard call, and
I'll address this in v3.

> > +       BUG();
>
> This BUG() is new and not mentioned in the commit text. Why can't we
> just start failing all scm calls if we can't detect the calling
> convention?

Bjorn has requested that the BUG was introduced in v1:
https://lore.kernel.org/patchwork/patch/1148619/#1350062


> > +out:
> > +       pr_debug("QCOM SCM SMC Convention: %llu\n", 
> > qcom_smccc_convention);
>
> Maybe pr_info() is more appropriate. PSCI currently prints out the
> version info so maybe printing something like "QCOM SCM SMC_64 calling
> convention" will be useful for early debugging.

Sure, will do.

Thanks,

Elliot

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