On 09/30/2015 11:13 PM, Geert Uytterhoeven wrote:

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From: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <redacted>
---
    arch/arm/boot/dts/r8a7791.dtsi | 22 ++++++++++++++++++++++
    1 file changed, 22 insertions(+)

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     When the USB-DMAC driver is enabled, this causes kernel oops on at
least
the R8A7791 Henninger/Porter boards (haven't checked the others yet) with
renesas-devel-20150928-v4.3-rc3 and even earlier tag. The oops can only
be
seen with the earlyprintk=serial kernel parameter, otherwise the kernel
just
hangs with a blank console.

My current kernel on r8a7791/koelsch has CONFIG_RENESAS_USB_DMAC=y and
boots
fine.

renesas-devel-20150928-v4.3-rc3 with shmobile_defconfig +
CONFIG_RENESAS_USB_DMAC=y also boots fine.

    Indeed, I was able to boot it all the way on Henninger.

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Do I need to enable/disable config options to trigger this?

    It appears so. I just don't know what -- the diff between my .config and
shmobile_defconfig is 150+ hunks. :-(

   OK, my shot in the dark proved helpful: it's the kernel preemption mode -- 
shmobile_defconfig has CONFIG_PREEMPT_NONE, my .config has CONFIG_PREEMPT!

Can you please send me your .config by private email?

   OK.

Thanks!

Gr{oetje,eeting}s,

MBR, Sergei