Re: [Xen-devel] [Xen-ARM] Modify the clock frequency for early printk

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hello,

On 17/04/14 18:49, HyonYoung Choi wrote:
> Hi Anthony and Julien,
>
> We are trying to run Xen 4.4 on the Arndale Octa board (Exynos 5420).
>
> The Xen and dom0's kernel is successfully loaded but Xen cannot start.
> The last output information in serial console is Starting kernel.
>
> In order to figure out the reason, we tried to use the early_printk to
> print out the message before console is initialized. However, the
> message we got is some garbling message after the "Start kernel..."
> message. Julien suggests this may be caused by the different rate of
> clock on Exynos 5420 and Exynos 5250.
>
> We looked at the file xen/arch/arm/arm32/debug-exynos4210.inc, the clock
> it chooses is MPLL 800MHz, but based on the output of our Exynos 5420
> board, our clock information is as follows:
>
> CPU: Exynos5420 Rev2.0 [Samsung SOC on SMP Platform Base on ARM CortexA15]
>
> APLL = 800MHz, KPLL = 600MHz
>
> MPLL = 532MHz, BPLL = 800MHz
>
> Our question is:
> 1) Is there any patch for the debug-exynos4210.inc file to support our
> board?
> 2) How should we change the code in debug-exynos4210.inc file to make it
> work on our board?
> 3) We tried to find the manual of setting the clocks so that we can
> change the following code accordingly. However, we cannot find it. Could
> you please refer to us some manual to achieve that?
In the patch I sent you earlier, can you try to replace
EARLY_PRINTK_INIT_UART := y

by

EARLY_PRINTK_INIT_UART := n

You have to clean the repo and recompile xen.

Regards,

--
Julien Grall

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