[U-Boot] [PATCH v3] sf: Add auto detection of 4-byte mode (vs standard 3-byte mode)

[York Sun]

Guys,

Let get back to the original thread. Since Rajat's first reply, the
message id has been changed. All the comments were not captured by
patchwork.

On 10/11/18 07:50, Stefan Roese wrote:
> Some SPI NOR chips only support 4-byte mode addressing. Here the default
> 3-byte mode does not work and leads to incorrect accesses. This patch
> now reads the 4-byte mode status bit (in this case in the CR register
> of the Macronix SPI NOR) and configures the SPI transfers accordingly.
> 
> This was noticed on the LinkIt Smart 7688 modul, which is equipped with
> an Macronix MX25L25635F device. But this device does *NOT* support
> switching to 3-byte mode via the EX4B command.
> 
> This should also work when the bootrom configures the SPI flash to
> 4-byte mode and runs U-Boot after this. U-Boot should dectect this
> mode (if the 4-byte mode detection is available for this chip) and
> use the correct OPs in this case.

>From what I read, Rajat's method is to extend the controller driver to
support read SFDP and default to 4-byte mode if supported, or
overwritten by user's flag. Stefan's method is to read 4-byte status bit
and doesn't change controller driver.

Is the default value of this 4-byte status bit valid and correct for all
cases?

Rajat, without your patch set, does Stefan's solution work for your board?

York