Hi York,
On 25.10.18 17:49, York Sun wrote:
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.
I also wondered about this. Seems to have happened at some top-posting
quite at the beginning of this thread.
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.
Yes, the last sentence it correct.
Is the default value of this 4-byte status bit valid and correct for all
cases?
This 4-byte address status bit implementation is SPI NOR chip
specific (vendor specific?). With Simon's help we already support
2 vendors now. Extending for other vendors / chips is fairly
easy.
Thanks,
Stefan
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