[PATCH] [RFC] ARM: imx: add smp support for imx7d

Jan Kiszka jan.kiszka at siemens.com
Tue Sep 22 10:59:44 EDT 2020

On 22.09.20 13:34, Marek Vasut wrote:
> On 9/22/20 8:27 AM, Shawn Guo wrote:
>> On Tue, Sep 22, 2020 at 2:22 PM Shawn Guo <shawnguo at kernel.org> wrote:
>>> On Thu, Sep 17, 2020 at 06:08:14PM +0200, Marek Vasut wrote:
>>>> From: Anson Huang <b20788 at freescale.com>
>>>> Add SMP support for i.MX7D, including CPU hotplug support, for
>>>> systems where TFA is not present.
>>> These systems are not supported by upstream kernel.  Sorry.
>> I meant for systems without PSCI support actually.
> Is there any specific reason for that ?
> The SoC works fully well with mainline U-Boot and without TFA, except
> the code for bringing up the second core is missing from mainline and
> that is all that is missing. PSCI is unnecessary extra complexity here.

We are coming from vendor kernels and would like to base our products on 
mainline for $countless-good-reasons. With the vendor kernels, this 
"classic" way of booting worked fine, with historic bootloaders and also 
with current mainline U-Boot.

If PSCI support is mandated, we would now be unable to migrate devices 
in the field that should not or cannot receive a bootloader update 
because existing deployments generally do not ship TF-A or any other 
PSCI implementation on ARMv7 - there was mostly no use for it (and there 
will likely be none, except for CPU onlining). Would be a shame.

So I'd also like to understand what speaks against a merge, provided 
this patch does not break other cases or make the code significantly 
more complex and harder to maintain.


Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

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