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Re: Deprecate the ppc405 boards in QEMU?


From: Thomas Huth
Subject: Re: Deprecate the ppc405 boards in QEMU?
Date: Wed, 6 Oct 2021 09:25:39 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0

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. Binary can be found here:

 http://people.redhat.com/~thuth/data/u-boot-taihu-skip-sdram.bin

Christophe, maybe that's already enough for you to boot a Linux kernel with the "taihu" board? (or do you need the ref405ep board instead?)

I've also attached the patch with my modifications to u-boot.

To build the u-boot firmware:

 git clone git://git.denx.de/u-boot.git
 cd u-boot
 git checkout 123b6cd7a4f75536734a7bff97db6eebce614bd1~1
 patch -p1 -i .../u-boot-taihu.patch
 make taihu_defconfig CROSS_COMPILE=powerpc-...
 make CROSS_COMPILE=powerpc-...

... if the linker complains at the end, remove some features from the ".config" file, like CONFIG_CMD_NFS, and run make again.

 Thomas

Attachment: u-boot-taihu.patch
Description: Text Data


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