[RFC PATCH 0/6] spi: Add OSPI PHY calibration support for spi-cadence-quadspi

[Michael Walle]

Am 2021-03-11 20:12, schrieb Pratyush Yadav:
> The main problem here is telling the controller where to find the
> pattern and how to read it. This RFC uses nvmem cells which point to a
> fixed partition containing the data to do the reads. It depends on [0]
> and [1].
> 
> The obvious problem with this is it won't work when the partitions are
> defined via command line. I don't see any good way to add nvmem cells 
> to
> command line partitions. I would like some help or ideas here. We don't
> necessarily have to use nvmem either. Any way that can cleanly and
> consistently let the controller find out where the pattern is stored is
> good.

The NXP LS1028A SoC has a similar calibration (although there its done
in hardware it seems) and there the datasheet mentions there are flash
devices which supports a preamble before a read function. The preamble
is then some kind of learning pattern. Did you see a flash which 
actually
supports that in the wild? I can't find any publicly available 
datasheets
of 8bit I/O SPI NOR flashes.

-michael