[flashrom] flashrom as programmer slow because it reads the whole SPI Flash contents before writing anything

[Carl-Daniel Hailfinger]

Hi Ruben,

On 11.01.2016 14:58, R. Diez wrote:
> I am trying to use flashrom with a fast generic FTDI FT2232H adapter
> as an SPI Flash programmer in a small production line.
>
> The SPI Flash chip can hold 8 MiB of data, but we are only using the
> first 512 KiB of it.
>
> I found flashrom to be surprisingly slow. I started digging and the
> step "Reading old flash chip contents..." is taking minutes.

If you can switch your production line to use flashrom on a Raspberry Pi
or a Beaglebone Black for SPI programming with the SPI pins on those
boards, reading a flash chip will only take seconds and writes will be
really fast as well because the per-command latency is almost zero.
With a SPI frequency of 8 MHz and a flash chip size of 8 MiB, reading
the whole chip on a RPi or BBB takes
roughly 9 seconds (to be precise, 8388608/256*(4+256)*8/8000000 seconds).
For FT2232 based programmers, you get a lot of USB overhead (mostly
latency) which makes reading slow, but writing is even worse.

Regards,
Carl-Daniel