[PATCH] ARM64: juno: add NOR flash to device tree

Mark Rutland mark.rutland at arm.com
Mon Oct 19 03:29:32 PDT 2015

On Mon, Oct 19, 2015 at 11:17:01AM +0100, Sudeep Holla wrote:
> On 18/10/15 10:25, Linus Walleij wrote:
> >On Thu, Oct 15, 2015 at 5:30 PM, Sudeep Holla <sudeep.holla at arm.com> wrote:
> >>Me
> >>>  Results after
> >>
> >>Just a note on this: we can't enable these when CPUIDLE is enabled as
> >>the firmware assumes the flash is always in read mode while Linux leaves
> >>NOR flash in "read id" mode after initialization.
> >
> >Sorry I'm too unfamiliar with this lingo. Can you give me some detail
> >on what "read mode" and "read id" mode is all about?
> >
> OK, sorry for that I just quoted from my understanding. Here is the
> actual one from the data sheet:
> "The device can be in any of four read states: Read Array, Read
>  Identifier, Read Status or Read Query. Upon power-up, or after a reset,
>  the device defaults to Read Array. To change the read state, the
>  appropriate read command must be written to the device..."
> After the driver gets initialized, it usually leaves the device in Read
> Identifier state as the last command sent is to read ID from the chip.
> >>So until the firmware is ready to handle that, we can't enabled both
> >>on Juno. We had same issue even on TC2. I will follow up internally to
> >>see if we can fix on Juno at-least.
> >
> >Sounds like something that should be fixed for all Versatile
> >Express that have cpuidle?
> >
> Correct, I just mentioned so that if you see/get any boot issue report
> with NOR flash and CPUIdle enabled, you will have the background instead
> of investigating the known issue again.

Also, for non U-Boot systems I was under the impression that the flash
was effectively owned by EFI (for variable storage), so it doesn't seem
like a sensible idea to me to poke the flash behind its back in that

Given that, I'm not sure that the flash node should be enabled by
default in the DT.



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