On Thu, May 30, 2019 at 11:11 AM Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
> Accessing the NOR flash memory from the kernel will disrupt CPU sleep/
> idles states and CPU hotplugging. We need to disable this DT node by
> default. Setups that want to access the flash can modify this entry to
> enable the flash again but also ensuring to disable CPU idle states and
> CPU hotplug.
>
> The platform firmware assumes the flash is always in read mode while
> Linux kernel driver leaves NOR flash in "read id" mode after
> initialization. If it gets used actively, it can be in some other state.
>
> So far we had not seen this issue as the NOR flash drivers in kernel
> were not enabled by default. However it was enable in multi_v7 config by
> Commit 5f068190cc10 ("ARM: multi_v7_defconfig: Enable support for CFI NOR FLASH")
>
> So, let's mark the NOR flash disabled so that the platform can boot
> again. This based on:
> Commit 980bbff018f6 ("ARM64: juno: disable NOR flash node by default")
>
> Cc: Liviu Dudau <liviu.dudau@xxxxxxx>
> Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
It's a bit sad that this cannot be easily fixed (I don't know if it can even
be fixed with firmware updates?), it's kind of useful to be able to
update the flash from within Linux, as that mimics what pretty much
every IoT device (such as routers) is doing and would be nince for
an OpenWrt port.
Yours,
Linus Walleij
