Re: Deprecate the ppc405 boards in QEMU?

[Thomas Huth]

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

u-boot-taihu.patch
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