Re: [PATCH] mtd: spi-nor: only apply reset hacks to broken hardware

[Brian Norris <computersforpeace@gmail.com>]

On Tue, Aug 07, 2018 at 12:39:01PM -0600, Rob Herring wrote:
> On Tue, Jul 31, 2018 at 03:35:50PM -0700, Brian Norris wrote:
> > One reason I didn't specifically say something like "not connected", is
> > because IIUC it's actually *possible* to have a robust boot sequence
> > without the RESET# pin -- e.g., if your boot ROM hardcoded a software
> > reset command (just because it's not really standardized doesn't mean
> > one can't do it).
> 
> Based on that, then it sounds like you need a specific compatible string 
> so you too can know how to s/w reset the device.

We do also support compatible properties for these chips, where needed.
But I don't think that's really needed.

> I guess you are assuming a bootloader didn't leave the flash in an 
> unknown addressing state?

For some of these address states (at least, 3-byte vs. 4-byte
addressing), we can still identify the device independently; the READ ID
command works in either mode.

The problem is that a boot ROM is rarely as complex as a Linux driver
and probably can't be updated. And they usually do stupid things anyway.
So *that's* where you need a well-defined entry state for the flash.

Brian