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
Thomas
