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Date:      Wed, 25 Jun 2025 13:11:32 -0700
From:      Mark Millard <marklmi@yahoo.com>
To:        "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net>
Cc:        Andrew Turner <andrew@freebsd.org>, dev-commits-src-main@freebsd.org
Subject:   Re: git: 288ba78edcfd - main - dev/psci: Check for functions before calling
Message-ID:  <7D17FF6C-DFD8-4921-A50F-B4A196EE86E6@yahoo.com>
In-Reply-To: <3s789nos-rq00-6n4q-46pq-280r4n3q22q6@yvfgf.mnoonqbm.arg>
References:  <60E32387-B0BA-4ADD-A897-DC988136D2F9.ref@yahoo.com> <60E32387-B0BA-4ADD-A897-DC988136D2F9@yahoo.com> <3s789nos-rq00-6n4q-46pq-280r4n3q22q6@yvfgf.mnoonqbm.arg>

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On Jun 25, 2025, at 12:48, Bjoern A. Zeeb =
<bzeeb-lists@lists.zabbadoz.net> wrote:

> On Wed, 25 Jun 2025, Mark Millard wrote:
>=20
>> Andrew Turner <andrew_at_FreeBSD.org> wrote on
>> Date: Wed, 25 Jun 2025 11:22:51 UTC :
>>=20
>>> The branch main has been updated by andrew:
>>>=20
>>> URL: =
https://cgit.FreeBSD.org/src/commit/?id=3D288ba78edcfd82b4b558a46fae78e407=
6acbe200
>>>=20
>>> commit 288ba78edcfd82b4b558a46fae78e4076acbe200
>>> Author: Andrew Turner <andrew@FreeBSD.org>
>>> AuthorDate: 2025-06-24 16:47:28 +0000
>>> Commit: Andrew Turner <andrew@FreeBSD.org>
>>> CommitDate: 2025-06-24 17:45:42 +0000
>>>=20
>>> dev/psci: Check for functions before calling
>>>=20
>>> In the SMCCC TRNG and Errata ABI drivers check if the version
>>> functions are implemented before calling them. Without this the =
firmware
>>> may complain about an unimplemented function being called.
>>>=20
>>> Reported by: bz
>>> Reviewed by: bz
>>> Sponsored by: Arm Ltd
>>> Differential Revision: https://reviews.freebsd.org/D50978
>>> ---
>>=20
>>=20
>> I wonder if a debug mode or verbose mode should report
>> the !=3D SMCCC_RET_SUCCESS cases for smccc_arch_features.
>> If this change had already been in place, the older
>> status might not have been noticed. As bz wrote
>> elsewhere:
>>=20
>> "That said seems like it's still a good idea to add
>> these bits to my TF-A."
>>=20
>> Having a way to check on if a TF-A instance is too
>> old to have a known status for handling things that
>> are now requested could be a good thing.
>=20
> Please read the comments on the review.

If you mean the text:

QUOTE
If the firmware doesn't implement the Errata ABI then we may
enable a workaround in the kernel even if we don't need to,
e.g. when the firmware already has a workaround, or the
combination of HW means it's not needed
END QUOTE

Sometimes that might be fine. But other times updating the
TF-A may be more appropriate. Thus, sometimes one might
want to learn about which workarounds (or no-ops) are
being done because the TF-A involved does not claim to
even have a feature. Then one can consider what is
appropriate for the TF-A, possibly choosing to update
it for some of what has workarounds/no-ops in the kernel.

So, to some extent my suggestion generalizes beyond the
2 specific messages that you got and the specific changes
made for those.

It is only a suggestion, possibly not a very valuable one.

=3D=3D=3D
Mark Millard
marklmi at yahoo.com




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