Re: Deprecate the ppc405 boards in QEMU?

From: Thomas Huth <thuth@redhat.com>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: "Christophe Leroy" <christophe.leroy@c-s.fr>,
	"Peter Maydell" <peter.maydell@linaro.org>,
	dbarboza@redhat.com, "Alexey Kardashevskiy" <aik@ozlabs.ru>,
	"QEMU Developers" <qemu-devel@nongnu.org>,
	"Christophe Leroy" <christophe.leroy@csgroup.eu>,
	"Greg Kurz" <groug@kaod.org>, "Alexander Graf" <agraf@csgraf.de>,
	qemu-ppc <qemu-ppc@nongnu.org>,
	"Wainer dos Santos Moschetta" <wainersm@redhat.com>,
	"Cleber Rosa" <crosa@redhat.com>,
	"Hervé Poussineau" <hpoussin@reactos.org>,
	"Philippe Mathieu-Daudé" <philmd@redhat.com>,
	"Cédric Le Goater" <clg@kaod.org>
Subject: Re: Deprecate the ppc405 boards in QEMU?
Date: Mon, 11 Oct 2021 15:24:36 +0200	[thread overview]
Message-ID: <bcdf63a4-8d22-8b25-d980-7fc574f80e82@redhat.com> (raw)
In-Reply-To: <YWQB1FMhQfmqRYxN@yekko>

On 11/10/2021 11.20, David Gibson wrote:
> On Mon, Oct 11, 2021 at 10:10:36AM +0200, Thomas Huth wrote:
>> On 06/10/2021 09.25, Thomas Huth wrote:
>>> On 05/10/2021 23.53, BALATON Zoltan wrote:
>>> [...]
>>>> Maybe these 405 boards in QEMU ran with modified firmware where the
>>>> memory detection was patched out but it seems to detect the RAM so I
>>>> wonder where it gets that from. Maybe by reading the SDRAM
>>>> controller DCRs ppc4xx_sdram_init() sets up. Then I'm not sure what
>>>> it needs the SPD for, I forgot how this worked on sam460ex. Maybe
>>>> for the speed calibration, so could be it detects ram by reading
>>>> DCRs then tries to get SPD data and that's where it stops as i2c is
>>>> not emulated on taihu. This could be confirmed by checking what it
>>>> pokes with -d guest_errors that shows accesses to missing devices
>>>> but don't know where 405 has the i2c controller and if it's the same
>>>> as newer SoCs. If so that could be reused and an i2c bus could be
>>>> added with the SPD data like in sam460ex to make u-boot happy or you
>>>> could skip this in u-boot.
>>>
>>> FWIW, I've just tried the latter (skipping the sdram init in u-boot),
>>> and indeed, I can get to the u-boot prompt now.
>> [...]> I've also attached the patch with my modifications to u-boot.
>>
>> FYI, the changes can now be found on this branch here:
>>
>>   https://gitlab.com/huth/u-boot/-/commits/taihu
>>
>> I also added a gitlab-CI file, so you can now download the u-boot.bin as an
>> artifact from the corresponding pipeline, e.g.:
>>
>>   https://gitlab.com/huth/u-boot/-/jobs/1667201028
> 
> Thanks.
> 
> Are you going to send a v2 of your proposed deprecation patches?

No, since there was interest in keeping the 405 boards for testing the 405 
code in the Linux kernel, and since there is now a way to do at least some 
very basic testing of these boards (with the u-boot firmware), I don't plan 
to respin the deprecation patch. I just sent a patch for adding the boards 
to our CI instead:

  https://lists.gnu.org/archive/html/qemu-devel/2021-10/msg02072.html

  Thomas