linux-kernel - Re: [PATCH] MIPS: ralink: mt7621: do memory detection on KSEG1

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Date:   Wed, 16 Feb 2022 20:54:23 +0100
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Chuanhong Guo <gch981213@...il.com>
Cc:     linux-mips@...r.kernel.org, Rui Salvaterra <rsalvaterra@...il.com>,
        Ilya Lipnitskiy <ilya.lipnitskiy@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MIPS: ralink: mt7621: do memory detection on KSEG1

On Fri, Feb 11, 2022 at 08:13:44AM +0800, Chuanhong Guo wrote:
> 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: 139c949f7f0a MIPS: ("ralink: mt7621: add memory detection support")
> Reported-by: Rui Salvaterra <rsalvaterra@...il.com>
> Signed-off-by: Chuanhong Guo <gch981213@...il.com>
> ---
>  arch/mips/ralink/mt7621.c | 36 +++++++++++++++++++++++-------------
>  1 file changed, 23 insertions(+), 13 deletions(-)

applied to mips-fixes.

Thomas.

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