[PATCH] ARM: Kirkwood: Fix crash when neither NAND nor SPI

Andrew Lunn andrew at lunn.ch
Fri Jun 8 14:43:17 EDT 2012

> > However, all current systems have either SPI FLASH or NAND, since that
> > is how these devices boot. So, under normal conditions, this clock is
> > always used, and so never gets turned off as being unused.
> What if your filesystems are on devices other than flash (I use an SD
> card on my Sheevaplugs). In that case flash isn't used at all by the
> Linux kernel and could be safely turned off. I'm not saying that this is
> worth the hassle, just pointing out that flash may be unused by Linux on
> some systems.

The current sheevaplug code sets up the nand driver and mtd
partitions. That is sufficient to ensure the clock is kept on. It does
not matter if a partitions are used or not.

I in fact use a similar system to you. I typically use kirkwood
devices which are NAS boxes and i have the root file system on the
disk and i tftpboot the kernel. The SPI flash is unused, but its still
made available via mtd.

Problems will however come when somebody creates a box which really
does boot from disk and skips NAND and SPI-FLASH in the DT description
of the device. That is why i like claiming this clock in the core
code, just to say there is something in the CPU core using it. 


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