Re: [PATCH v7 4/4] arm64: dts: Add Caninos Loucos Labrador v3

[Matheus Castello]

Em 9/22/20 7:26 AM, Catalin Marinas escreveu:
> On Tue, Sep 22, 2020 at 10:32:06AM +0200, Arnd Bergmann wrote:
> > On Tue, Sep 22, 2020 at 8:15 AM Manivannan Sadhasivam
> > <manivannan.sadhasivam@xxxxxxxxxx> wrote:
> > > On Mon, Sep 21, 2020 at 11:43:02PM -0300, Matheus Castello wrote:
> > > > +     /* Labrador v3 firmware does not support PSCI */
> > >
> > > Oops. This is unfortunate... I'm not sure if this is even acceptable for
> > > ARM64 machines.
> > >
> > > Let me add Olof and Arnd...
> >
> > Adding Catalin and Will for additional input as well, this is more their
> > area than ours.
> >
> > I don't think we have formalized this as a policy, but we clearly don't
> > want new boards to use the spin table hack. As there are other
> > boards using psci on the same chip, I don't think this is a
> > hardware bug.
>
> I fully agree, we shouldn't allow new boards to use the spin-table
> method unless EL3 is missing on the CPU implementation (not the case
> here; only the APM hardware has this issue). Unfortunately we missed
> another platform with A53, see commit bc66392d8258 ("arm64: dts: fsl:
> Add device tree for S32V234-EVB").
>
> The kernel relies on firmware for other things (power management, errata
> workarounds), so an SMC calling convention compliant firmware is highly
> recommended. I also don't see why it would be that hard to add PSCI.
> Even if you don't port something like Trusted Firmware, U-Boot has basic
> support for PSCI.
>
> So from my perspective, NAK on this patch.

Thanks Arnd and Catalin, this is really just a limitation of the 
bootloader developed by manufactures that comes embedded in the board. I 
will drop this in the next version.

> I'm tempted to also modify smp_spin_table_cpu_init() to print a big
> warning and return an error if this is attempted on new platforms. IOW,
> we make it a policy from now on.