linux-kernel - Re: [PATCH v2 1/1] arm64: dts: mediatek: mt8186: Increase CCI frequency

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Date:   Wed, 29 Nov 2023 14:22:43 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Mark Tseng <chun-jen.tseng@...iatek.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Chen-Yu Tsai <wenst@...omium.org>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v2 1/1] arm64: dts: mediatek: mt8186: Increase CCI
 frequency

Il 14/09/23 14:10, Mark Tseng ha scritto:
> The original CCI OPP table's lowest frequency 500 MHz is too low and causes
> system stalls. Increase the frequency range to 1.05 GHz ~ 1.4 GHz and adjust
> the OPPs accordingly.
> 
> Fixes: 32dfbc03fc26 ("arm64: dts: mediatek: mt8186: Add CCI node and CCI OPP table")
> 
> Signed-off-by: Mark Tseng <chun-jen.tseng@...iatek.com>

You ignored my comment [1] on the v1 of this patch.

Besides, I think that you should at least keep the 500MHz frequency for a
sleep-only/idle OPP to save power.

It would also be helpful to understand why you chose this new frequency range,
so if you can, please put some numbers in the commit description, showing the
stall in terms of requested BW vs actual BW (as I'd imagine that a 2x increase
in CCI frequency means that we need *twice* the bandwidth compared to what we
have for the workloads that are stalling the system).

[1]: https://lore.kernel.org/all/799325f5-29b5-f0c0-16ea-d47c06830ed3@collabora.com/

Regards,
Angelo