linux-kernel - Re: [PATCH] soc: imx: gpcv2: keep i.MX8MM VPU-H1 bus clock active

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Message-ID: <CAHCN7x+5HXJEdRKbm80trpNwxZRAMhX12+FQ0JeVvrqKpKf+BA@mail.gmail.com>
Date:   Thu, 31 Mar 2022 06:32:13 -0500
From:   Adam Ford <aford173@...il.com>
To:     Lucas Stach <l.stach@...gutronix.de>
Cc:     arm-soc <linux-arm-kernel@...ts.infradead.org>,
        Tim Harvey <tharvey@...eworks.com>,
        Adam Ford-BE <aford@...conembedded.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Peng Fan <peng.fan@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] soc: imx: gpcv2: keep i.MX8MM VPU-H1 bus clock active

On Thu, Mar 31, 2022 at 4:28 AM Lucas Stach <l.stach@...gutronix.de> wrote:
>
> Hi Adam, hi Shawn,
>
> Am Samstag, dem 20.11.2021 um 13:39 -0600 schrieb Adam Ford:
> > Enable the vpu-h1 clock when the domain is active because reading
> > or writing to the VPU-H1 IP block cause the system to hang.
> >
> > Fixes: 656ade7aa42a ("soc: imx: gpcv2: keep i.MX8M* bus clocks enabled")
> > Signed-off-by: Adam Ford <aford173@...il.com>
> >
> > diff --git a/drivers/soc/imx/gpcv2.c b/drivers/soc/imx/gpcv2.c
> > index b8d52d8d29db..7b6dfa33dcb9 100644
> > --- a/drivers/soc/imx/gpcv2.c
> > +++ b/drivers/soc/imx/gpcv2.c
> > @@ -734,6 +734,7 @@ static const struct imx_pgc_domain imx8mm_pgc_domains[] = {
> >                       .map = IMX8MM_VPUH1_A53_DOMAIN,
> >               },
> >               .pgc   = BIT(IMX8MM_PGC_VPUH1),
> > +             .keep_clocks = true,
> >       },
> >
> I missed this patch and just stumbled across it when looking at the git
> history. I don't think this patch is correct. The H1 GPC domain does
> not even have clocks assigned in the DT, so there is nothing to keep
> active. Also H1 is not a MIX domain, so it should not keep any bus
> clocks active, that is the job of the VPUMIX domain.
>
> While this patch is a no-op, as far as I can see, it still seems wrong
> and I think it should be reverted.

At the time I sent this, I was working with some people in the media
group to split the G1 and G2 up in the imx8mq and add G1 and G2
support in the imx8mm.  I had inquired about the feasibility of using
the H1 encoder on the imx8mm, but I needed to read some registers from
the IP block to see which features were fused out.  I tried several
different options to get the H1 to not hang when reading registers,
and that was the only solution I found that worked.  I thought it odd
as well since the G1 and G2 decoders didn't appear to need this.
However, during the course of my investigation, I learned that the
JPEG encoder was fused out of the imx8mm, and there wasn't a plan to
add VP8 or H.264 encodering any time soon.   Since it is, as you put
it, a no-op, I have no objections to reverting it.

adam
>
> Regards,
> Lucas
>