Le 11/02/2020 à 17:06, Larry Finger a écrit :
On 2/11/20 12:55 AM, Christophe Leroy wrote:
Le 10/02/2020 à 13:55, Larry Finger a écrit :
On 2/9/20 12:19 PM, Christophe Leroy wrote:
Do you have CONFIG_TRACE_IRQFLAGS in your config ?
If so, can you try the patch below ?
https://patchwork.ozlabs.org/patch/1235081/
Otherwise, can you send me your .config and tell me exactly where it
stops during the boot.
Christophe,
That patch did not work. My .config is attached.
It does boot if CONFIG_VMAP_STACK is not set.
The console display ends with the "DMA ranges" output. A screen shot
is also appended.
Larry
Hi,
I tried your config under QEMU, it works.
In fact your console display is looping on itself, it ends at "printk:
bootconsole [udbg0] disabled".
Looks like you get stuck at the time of switching to graphic mode.
Need to understand why.
I'm not surprised that a real G4 differs from QEMU. For one thing, the
real hardware uses i2c to connect to the graphics hardware.
I realized that the screen was not scrolling and output was missing. To
see what was missed, I added a call to btext_clearscreen(). As you
noted, it ends at the bootconsole disabled statement.
As I could not find any console output after that point, I then turned
off the bootconsole disable. I realize this action may cause a different
problem, but in this configuration, the computer hit a BUG Unable to
handle kernel data access at 0x007a84fc. The faulting instruction
address was 0x00013674. Those addresses look like physical, not virtual,
addresses.
Can you send me a picture of that BUG Unable to handle kernel data
access with all the registers values etc..., together with the matching
vmlinux ?
First thing is to identify where we are when that happens. That mean see
what is at 0xc0013674. Can be done with 'ppc-linux-objdump -d vmlinux'
(Or whatever your PPC objdump is named) and get the function code.
Then we need to understand how we reach that function and why it tries
to access a physical address.
Another thing I'm thinking about, not necessarily related to that
problem: Some buggy drivers do DMA from stack. This doesn't work anymore
with CONFIG_VMAP_STACK. Most of them can be detected with
CONFIG_DEBUG_VIRTUAL so you should activate it.
Christophe
