[FS#510] slow sysupgrade

[LEDE Bugs]

The following task has a new comment added:

FS#510 - slow sysupgrade
User who did this - Mathias Kresin (mkresin)

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Yes, the reason for the slow write/erase is 4K sector support (see FS#385).

I've initially enabled CONFIG_MTD_SPI_NOR_USE_4K_SECTORS for the sitecom wlr-6000 which has the firmware partition at a 4K boundary. Later I've enabled the kernel config option for more ramips subtargets with 4MByte flash boards, to not waste the already tight flash with to much padding.

Due to the fact that we build a single kernel per (sub)target all boards of that target have the  kernel option enabled.

What I was not aware at the time I enabled the kernel option is that 4K sectors are even supported by flash chips > 8 MByte. There isn't much benefit of using 4K sectors for flash chips of these sizes. It is rather that the disadvantage of slow write/erase outweighs.
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=510#comment3411