linux-kernel - Re: [PATCH v9 2/4] soc: mediatek: Init MT8173 scpsys driver earlier

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Date:   Mon, 31 Oct 2016 10:08:22 +0800
From:   James Liao <jamesjj.liao@...iatek.com>
To:     Matthias Brugger <matthias.bgg@...il.com>,
        Yong Wu <yong.wu@...iatek.com>
CC:     Sascha Hauer <kernel@...gutronix.de>,
        Rob Herring <robh@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Daniel Kurtz <djkurtz@...omium.org>,
        <srv_heupstream@...iatek.com>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v9 2/4] soc: mediatek: Init MT8173 scpsys driver earlier

On Mon, 2016-10-31 at 01:08 +0100, Matthias Brugger wrote:
> Hi James,
> 
> On 10/20/2016 10:56 AM, James Liao wrote:
> > Some power domain comsumers may init before module_init.
> > So the power domain provider (scpsys) need to be initialized
> > earlier too.
> >
> > Take an example for our IOMMU (M4U) and SMI. SMI is a bridge
> > between IOMMU and multimedia HW. SMI is responsible to
> > enable/disable iommu and help transfer data for each multimedia
> > HW. Both of them have to wait until the power and clocks are
> > enabled.
> >
> > So scpsys driver should be initialized before SMI, and SMI should
> > be initialized before IOMMU, and then init IOMMU consumers
> > (display/vdec/venc/camera etc.).
> >
> > IOMMU is subsys_init by default. So we need to init scpsys driver
> > before subsys_init.
> >
> > Signed-off-by: James Liao <jamesjj.liao@...iatek.com>
> > Reviewed-by: Kevin Hilman <khilman@...libre.com>
> > ---
> 
> I didn't applied this patch for now.
> I answered you in v7 of this series [1]. I would prefer to see if we can 
> fix that otherwise.
> 
> Would be great if you or Yong could provide some feedback.
> 
> Thanks,
> Matthias
> 
> [1] https://patchwork.kernel.org/patch/9397405/
> 
> >  drivers/soc/mediatek/mtk-scpsys.c | 19 ++++++++++++++++++-
> >  1 file changed, 18 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/soc/mediatek/mtk-scpsys.c b/drivers/soc/mediatek/mtk-scpsys.c
> > index fa9ee69..dd7a07d 100644
> > --- a/drivers/soc/mediatek/mtk-scpsys.c
> > +++ b/drivers/soc/mediatek/mtk-scpsys.c
> > @@ -613,4 +613,21 @@ static int scpsys_probe(struct platform_device *pdev)
> >  		.of_match_table = of_match_ptr(of_scpsys_match_tbl),
> >  	},
> >  };
> > -builtin_platform_driver(scpsys_drv);
> > +
> > +static int __init scpsys_drv_init(void)
> > +{
> > +	return platform_driver_register(&scpsys_drv);
> > +}
> > +
> > +/*
> > + * There are some Mediatek drivers which depend on the power domain driver need
> > + * to probe in earlier initcall levels. So scpsys driver also need to probe
> > + * earlier.
> > + *
> > + * IOMMU(M4U) and SMI drivers for example. SMI is a bridge between IOMMU and
> > + * multimedia HW. IOMMU depends on SMI, and SMI is a power domain consumer,
> > + * so the proper probe sequence should be scpsys -> SMI -> IOMMU driver.
> > + * IOMMU drivers are initialized during subsys_init by default, so we need to
> > + * move SMI and scpsys drivers to subsys_init or earlier init levels.
> > + */
> > +subsys_initcall(scpsys_drv_init);
> >

Hi Matthias,

I got it, thanks.


Hi Yong,

Is this patch still needed on latest kernel for IOMMU driver? Or we have
other solutions for IOMMU driver init?


Best regards,

James