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Re: PL011

From: Peter Maydell
Subject: Re: PL011
Date: Mon, 6 Jan 2020 10:38:09 +0000

On Sun, 5 Jan 2020 at 09:38, Shlomo Pongratz <address@hidden> wrote:
> Hi,
> I'm running Busybox/Linux one qemu-system-aarch64 with board virt.
> I see the following message in the boot log:
> [    1.775328] uart-pl011 9000000.pl011: no DMA platform data
> Other from that system seems to run normally.
> What is the meaning of this message?

It means that the kernel's pl011 driver has not found
any information in the device tree that would allow it to
use DMA. This is an 'information' level message, not an
error. For the QEMU virt board, we do indeed not have
any DMA controller provided; I suspect that if we did
emulate a DMA controller it wouldn't provide any
performance improvement and it would certainly be a
lot of extra complication (and for UART traffic pretty

Short answer: message is harmless, informational; just
ignore it.

-- PMM

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