linux-kernel - Re: [PATCH 05/13] memory: mtk-smi: Add device-link between smi-larb and smi-common

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Date:   Wed, 27 Feb 2019 22:33:05 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Evan Green <evgreen@...omium.org>
CC:     Joerg Roedel <joro@...tes.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Tomasz Figa <tfiga@...gle.com>,
        Will Deacon <will.deacon@....com>,
        <linux-mediatek@...ts.infradead.org>,
        <srv_heupstream@...iatek.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <iommu@...ts.linux-foundation.org>, Arnd Bergmann <arnd@...db.de>,
        <yingjoe.chen@...iatek.com>, <youlin.pei@...iatek.com>,
        Nicolas Boichat <drinkcat@...omium.org>
Subject: Re: [PATCH 05/13] memory: mtk-smi: Add device-link between smi-larb
 and smi-common

On Mon, 2019-02-25 at 15:54 -0800, Evan Green wrote:
> On Mon, Dec 31, 2018 at 8:52 PM Yong Wu <yong.wu@...iatek.com> wrote:
> >
> > Normally, If the smi-larb HW need work, we should enable the smi-common
> > HW power and clock firstly.
> > This patch adds device-link between the smi-larb dev and the smi-common
> > dev. then If pm_runtime_get_sync(smi-larb-dev), the pm_runtime_get_sync
> > (smi-common-dev) will be called automatically.
> >
> > Since smi is built-in driver like IOMMU and never unbound,
> > DL_FLAG_AUTOREMOVE_* is not needed.
> >
> > CC: Matthias Brugger <matthias.bgg@...il.com>
> > Suggested-by: Tomasz Figa <tfiga@...omium.org>
> > Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> > ---
> >  drivers/memory/mtk-smi.c | 16 +++++++---------
> >  1 file changed, 7 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/memory/mtk-smi.c b/drivers/memory/mtk-smi.c
> > index 9688341..30930e4 100644
> > --- a/drivers/memory/mtk-smi.c
> > +++ b/drivers/memory/mtk-smi.c
> > @@ -271,6 +271,7 @@ static int mtk_smi_larb_probe(struct platform_device *pdev)
> >         struct device *dev = &pdev->dev;
> >         struct device_node *smi_node;
> >         struct platform_device *smi_pdev;
> > +       struct device_link *link;
> >
> >         larb = devm_kzalloc(dev, sizeof(*larb), GFP_KERNEL);
> >         if (!larb)
> > @@ -310,6 +311,12 @@ static int mtk_smi_larb_probe(struct platform_device *pdev)
> >                 if (!platform_get_drvdata(smi_pdev))
> >                         return -EPROBE_DEFER;
> >                 larb->smi_common_dev = &smi_pdev->dev;
> > +               link = device_link_add(dev, larb->smi_common_dev,
> > +                                      DL_FLAG_PM_RUNTIME);
> 
> Doesn't this need to be torn down in remove()? You mention that it's
> built-in and never removed, but it does seem to have a remove()

The MTK IOMMU driver need depend on this SMI driver. the IOMMU is a
builtin driver, thus the SMI also should be a builtin driver.

Technically, If the driver is builtin, then the "remove" function can be
removed? If yes, I could use a new patch do it.

It looks the MACRO(builtin_platform_driver) only support one driver, but
we have two driver(smi-common and smi-larb) here.

> function that tears down everything else, so it seemed a shame to
> start leaking now. Maybe the AUTOREMOVE flag would do it.