linux-kernel - Re: [PATCH 2/2] mailbox: mtk-cmdq: Move pm_runimte_get and put to mbox_chan

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Message-ID: <CABb+yY1L+YGjf6O9UgPYkS2gWAdo=7QoojSAUNWC_8o7XtZQSg@mail.gmail.com>
Date: Tue, 18 Jun 2024 10:59:44 -0500
From: Jassi Brar <jassisinghbrar@...il.com>
To: Jason-JH Lin (林睿祥) <Jason-JH.Lin@...iatek.com>
Cc: "linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>, 
	Singo Chang (張興國) <Singo.Chang@...iatek.com>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>, Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>, 
	Project_Global_Chrome_Upstream_Group <Project_Global_Chrome_Upstream_Group@...iatek.com>, 
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, 
	"matthias.bgg@...il.com" <matthias.bgg@...il.com>, 
	"angelogioacchino.delregno@...labora.com" <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH 2/2] mailbox: mtk-cmdq: Move pm_runimte_get and put to
 mbox_chan_ops API

On Tue, Jun 18, 2024 at 3:42 AM Jason-JH Lin (林睿祥)
<Jason-JH.Lin@...iatek.com> wrote:
>
> On Mon, 2024-06-17 at 13:18 -0500, Jassi Brar wrote:
> >
......

> > As in, how often and long are the "channel idle" periods? And when
> > active, how many transfers/sec ?
> Is there any debug logs in mailbox can measure this?
>
> This mailbox channel is use to configure display hardware in every
> VSYNC, so the channel idle periods may be less than 16.66ms.
>
> It should call rx_callback() before VACTIVE, but sometimes it will be
> dropped by mbox_flush() if the new message is coming.
>
> > I see every TX is acked by one RX packet. How long is the typical gap
> > between a TX and its ack?
>
> Typical gap between a TX and its ack is less than 16.66ms.
>
So basically the usecase is driving some display at 60Hz. And I
believe the display is driven
continuously for at least some minutes ?
If so, RPM between xfers is not really in effect because the
autosuspend delay is 100ms while you
get() it every 16.66ms. So all that is happening is some variables
changed under a spinlock.
I think you should consider get/put RPM in cmdq_mbox_startup() and
cmdq_mbox_shutdown().

Thanks