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

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Message-ID: <CALjTZva7fKOzG7u4QYhZ+3ZGN2p5DV+fLh6WbFLFtSSfjKQ-ug@mail.gmail.com>
Date:   Fri, 11 Feb 2022 08:46:08 +0000
From:   Rui Salvaterra <rsalvaterra@...il.com>
To:     Chuanhong Guo <gch981213@...il.com>
Cc:     linux-mips@...r.kernel.org,
        Ilya Lipnitskiy <ilya.lipnitskiy@...il.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        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

Hi, Guo,

On Fri, 11 Feb 2022 at 00:14, Chuanhong Guo <gch981213@...il.com> 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.

[patch snipped]

No issues here, and it does seem to have fixed the RAM size detection
on my Redmi AC2100. It's always been a very sporadic failure here, so
I'll be keeping an eye on it to see if there are any further
misdetections. :)
In any case, feel free to add my

Tested-by: Rui Salvaterra <rsalvaterra@...il.com>

Thanks,
Rui