[PATCH u-boot-mvebu 1/2] arm: mvebu: turris_omnia: force 40 MHz speed on SPI NOR

[Marek Behún]

On Fri,  9 Jul 2021 16:56:13 +0200
Marek Behún <marek.behun at nic.cz> wrote:

> Commit e2e95e5e2542 ("spi: Update speed/mode on change") changed the
> boot time on Turris Omnia from ~2.3s to over 8s, due to SPL loading
> main U-Boot from SPI NOR at 1 MHz instead of 40 MHz.
> 
> This is because the SPL code passes the CONFIG_SF_DEFAULT_SPEED option
> to spi_flash_probe(), and with the above commit spi_flash_probe()
> starts prefering this parameter instead of the one specified in
> device-tree.
> 
> The proper solution here would probably be to fix the SF subsystem to
> prefer the frequency specified in the device-tree, if it is present,
> but I am not sure what else will be affected on other boards with
> such a change. So until then we need a more simple fix.
> 
> Since the CONFIG_SF_DEFAULT_SPEED option is used by the code, put the
> correct value there for Turris Omnia. Also put the correct value to
> CONFIG_SF_DEFAULT_MODE and use 40 MHz when reading environment.

BTW this change is currently needed even if the other series (making
use of BootROM code to load main U-Boot instead of SPL doing it) is
accepted: commit e2e95e5e2542 also changed the behavior of the
  sf read / sf update
command - it is slower since it operates at 1 MHz now instead of 40 MHz
as specified in the device-tree.

Marek