[PATCH 21.02] ramips: mt7621: do memory detection on KSEG1

[Chuanhong Guo]

Hi!

On Mon, Feb 21, 2022 at 10:22 AM Szabolcs Hubai <szab.hu at gmail.com> wrote:
>
> From: Chuanhong Guo <gch981213 at gmail.com>
>
> It's reported that current memory detection code occasionally detects
> larger memory under some bootloaders.
> Current memory detection code tests whether address space wraps around
> on KSEG0, which is unreliable because it's cached.
>
> Rewrite memory size detection to perform the same test on KSEG1 instead.
> While at it, this patch also does the following two things:
> 1. use a fixed pattern instead of a random function pointer as the magic
>    value.
> 2. add an additional memory write and a second comparison as part of the
>    test to prevent possible smaller memory detection result due to
>    leftover values in memory.
>
> Fixes: 6d91ddf517 ("ramips: mt7621: add support for memory detection")
> Reported-by: Rui Salvaterra <rsalvaterra at gmail.com>
> Tested-by: Rui Salvaterra <rsalvaterra at gmail.com>
> Signed-off-by: Chuanhong Guo <gch981213 at gmail.com>
> (cherry picked from commit 2f024b79331141e2a62c9bf3601c803b26bde77b)
> [backport for OpenWrt 21.02 as it was reproducible with Kernel 5.4, see [1]]
> [1]: https://forum.openwrt.org/t/113081
> Tested-by: Dimitri Souza <dimitri.souza at gmail.com> [mt7621/archer-c6-v3]
> Signed-off-by: Szabolcs Hubai <szab.hu at gmail.com>

Merged. Thanks!

-- 
Regards,
Chuanhong Guo