linux-kernel - Re: [PATCH v9 03/13] media: hantro: Use syscon instead of 'ctrl' register

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Message-ID: <7c09d1ffbe79c3d6138258d0827613a1cc6544c4.camel@pengutronix.de>
Date:   Mon, 17 May 2021 15:46:20 +0200
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Ezequiel Garcia <ezequiel@...labora.com>,
        Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        p.zabel@...gutronix.de, mchehab@...nel.org, robh+dt@...nel.org,
        shawnguo@...nel.org, s.hauer@...gutronix.de, festevam@...il.com,
        lee.jones@...aro.org, gregkh@...uxfoundation.org,
        mripard@...nel.org, paul.kocialkowski@...tlin.com, wens@...e.org,
        jernej.skrabec@...l.net, hverkuil-cisco@...all.nl,
        emil.l.velikov@...il.com, "Peng Fan (OSS)" <peng.fan@....nxp.com>,
        Jacky Bai <ping.bai@....com>
Cc:     devel@...verdev.osuosl.org, devicetree@...r.kernel.org,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, linux-imx@....com,
        kernel@...gutronix.de, kernel@...labora.com, cphealy@...il.com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v9 03/13] media: hantro: Use syscon instead of 'ctrl'
 register

Am Montag, dem 17.05.2021 um 10:23 -0300 schrieb Ezequiel Garcia:
> On Mon, 2021-05-17 at 12:52 +0200, Lucas Stach wrote:
> > Hi Ezequiel,
> > 
> > Am Sonntag, dem 16.05.2021 um 19:40 -0300 schrieb Ezequiel Garcia:
> > > Hi Lucas,
> > > 
> > > On Fri, 2021-04-16 at 12:54 +0200, Lucas Stach wrote:
> > > > Am Mittwoch, dem 07.04.2021 um 09:35 +0200 schrieb Benjamin Gaignard:
> > > > > In order to be able to share the control hardware block between
> > > > > VPUs use a syscon instead a ioremap it in the driver.
> > > > > To keep the compatibility with older DT if 'nxp,imx8mq-vpu-ctrl'
> > > > > phandle is not found look at 'ctrl' reg-name.
> > > > > With the method it becomes useless to provide a list of register
> > > > > names so remove it.
> > > > 
> > > > Sorry for putting a spoke in the wheel after many iterations of the
> > > > series.
> > > > 
> > > > We just discussed a way forward on how to handle the clocks and resets
> > > > provided by the blkctl block on i.MX8MM and later and it seems there is
> > > > a consensus on trying to provide virtual power domains from a blkctl
> > > > driver, controlling clocks and resets for the devices in the power
> > > > domain. I would like to avoid introducing yet another way of handling
> > > > the blkctl and thus would like to align the i.MX8MQ VPU blkctl with
> > > > what we are planning to do on the later chip generations.
> > > > 
> > > > CC'ing Jacky Bai and Peng Fan from NXP, as they were going to give this
> > > > virtual power domain thing a shot.
> > > > 
> > > 
> > > It seems the i.MX8MM BLK-CTL series are moving forward:
> > > 
> > > https://patchwork.kernel.org/project/linux-arm-kernel/list/?series=479175
> > > 
> > > ... but I'm unable to wrap my head around how this affects the
> > > devicetree VPU modelling for i.MX8MQ (and also i.MX8MM, i.MX8MP, ...).
> > > 
> > > 
> > For the i.MX8MQ we want to have the same virtual power-domains provided
> > by a BLK-CTRL driver for the VPUs, as on i.MX8MM. This way we should be
> > able to use the same DT bindings for the VPUs on i.MX8MQ and i.MX8MM,
> > even though the SoC integration with the blk-ctrl is a little
> > different.
> > 
> 
> AFAICS, there's not support for i.MX8MP VPU power domains. I suppose
> we should make sure we'll be able to cover those as well.
> 
> Will i.MX8MP need its own driver as well?
> > 

I haven't looked too closely at the 8MP VPU subsystem yet, but I expect
it to be slightly different again so it will need changes to the blk-
ctrl driver. But that's the whole point of this virtual power domain
exercise: abstract away the SoC specific things in the blk-ctrl driver,
so the VPU driver doesn't need to care about them.

Regards,
Lucas