linux-kernel - RE: [PATCH 2/2] firmware: imx: MU IRQ group number should be 7

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Message-ID: <AM6PR04MB49668CCFFB4439B051E99A3B80D00@AM6PR04MB4966.eurprd04.prod.outlook.com>
Date:   Fri, 24 Apr 2020 02:51:09 +0000
From:   Aisheng Dong <aisheng.dong@....com>
To:     Anson Huang <anson.huang@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "ben.dooks@...ethink.co.uk" <ben.dooks@...ethink.co.uk>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH 2/2] firmware: imx: MU IRQ group number should be 7

> From: Anson Huang <anson.huang@....com>
> Sent: Friday, April 24, 2020 10:36 AM
> 
> > -----Original Message-----
> > From: Aisheng Dong <aisheng.dong@....com>
> > Sent: 2020年4月24日 10:33
> > To: Anson Huang <anson.huang@....com>; shawnguo@...nel.org;
> > s.hauer@...gutronix.de; kernel@...gutronix.de; festevam@...il.com;
> > ben.dooks@...ethink.co.uk; linux-arm-kernel@...ts.infradead.org;
> > linux-kernel@...r.kernel.org
> > Cc: dl-linux-imx <linux-imx@....com>
> > Subject: RE: [PATCH 2/2] firmware: imx: MU IRQ group number should be
> > 7
> >
> > > From: Anson Huang <Anson.Huang@....com>
> > > Sent: Friday, April 24, 2020 7:07 AM
> > >
> > > The MU IRQ group number should be 7 instead of 4.
> > >
> > > Signed-off-by: Anson Huang <Anson.Huang@....com>
> >
> > Are we using others IRQ group?
> > If not, this change may slow down the irq handling speed.
> 
> The irq handling is using work queue, NOT in ISR, so the speed is NOT that
> sensitive.

SCU IPC is shared by the whole system, each SCU transfer takes about 10~20 us.
Here you may waste 30~60us if not really used.

> The scu group irq driver should provide full functions, as other drivers using it
> may enable the group they want.

Below are extra GROUPs you're going to add:
#define SC_IRQ_GROUP_SYSCTR     4U   /*!< System counter interrupts */
#define SC_IRQ_GROUP_REBOOTED   5U   /*!< Partition reboot complete */
#define SC_IRQ_GROUP_REBOOT     6U   /*!< Partition reboot starting */
Are we really going to use it? It seems I also didn't see any users in downstream tree.

Some functions provided by SCFW may not really used by Linux.
I think I's better to add them when we really need them, otherwise we benefit nothing
But wasting CPU mips.

Regards
Aisheng

> 
> Anson