Re: [PATCH v24 3/7] soc: mediatek: SVS: introduce MTK SVS engine

[Kevin Hilman <khilman@kernel.org>]

Hi Roger,


Roger Lu <roger.lu@mediatek.com> writes:

> The Smart Voltage Scaling(SVS) engine is a piece of hardware
> which calculates suitable SVS bank voltages to OPP voltage table.
> Then, DVFS driver could apply those SVS bank voltages to PMIC/Buck
> when receiving OPP_EVENT_ADJUST_VOLTAGE.
>
> Signed-off-by: Roger Lu <roger.lu@mediatek.com>
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Can SVS work with one or the other clusters disabled?  It seems like it
should still be able to work.  However, if you disable the 2nd cluster
(e.g. by passing `maxcpus=4` on the kernel command-line, the SVS driver
will fail to probe.

I dont' think it's a blocker for merging this series, but making the
probe a bit more robust so it can handle the cluster being disabled
would be nice additional fix for later.

For example, upstream kernel on mt8183-pumpkin board is very unstable
with the 2nd cluster enabled (I'm still trying to debug why), but I have
to boot with `maxcpus=4` on the cmdline, otherwise kernel fails to boot,
so that's how I noticed this probe failure with SVS.

Kevin