[Letux-kernel] [Lenny400] CI20: how to boot upstream kernel?

[H. Nikolaus Schaller]

Hi Mathieu,

> Am 10.05.2019 um 08:08 schrieb Mathieu Malaterre <malat at debian.org>:
> 
>> 
>> The 4.19 kernel is stuck with
>> 
>> [    0.968637] Waiting for root device /dev/mmcblk0p1...
>> 
>> although the mmc driver is loaded:
>> 
>> [    0.760598] jz4740-mmc 13460000.mmc: JZ SD/MMC card driver registered
>> [    0.767091] jz4740-mmc 13460000.mmc: Using DMA, 4-bit mode
>> 
>> Before I start a bisect to find which patch between 4.19 and 5.0 made it
>> work, I better ask the CI20 specialists here first...
> 
> https://patchwork.kernel.org/project/linux-mmc/list/?submitter=179601

Thanks for pointing to this patch set!

Unless I have missed something, all patches except the first one have been
backported to stable v4.19.40 so they should be effective. And the first one
doesn't seem to improve anything in my tests.

I have tried to git bisect and manual bisect and git log arch/mips/ingenic
but didn't find something in the jz47xx code or CI20 drivers that is obviously
related.

What I also tried is to cherry-pick the jz4780 dma changes introduced by
4.20 - but also no success.  So it might be a side-effect of some other driver.

Current status of my tests is that
v4.20-rc2	boots to login:
v4.20-rc1	kernel panics with page faults and strange things
v4.19.0		fails with "waiting for root device"
same for v4.18 and v4.14

Unfortunately, these kernel panics make it difficult to git bisect between
v4.19 and v4.20-rc2.

It also does not seem to make a difference if I use the ci20_defconfig
or my own (otherwise I could simply bisect the diff between both defconfigs).

Well, I could simply use 4.20-rc2 or later only, but v4.19 is currently the
latest longterm kernel. It is the base of our LetuxOS distribution, so I'd
prefer to get it working.

Therefore, I am a little lost in pinpointing the reason why I can't get any
v4.19.x kernel boot properly. Is there maybe a private v4.19.x tree that is
known to boot from SD card so that I could start comparisons?

BR and thanks,
Nikolaus