linux-kernel - Re: [PATCH v5 17/20] memory: mtk-smi: Get rid of need

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Date:   Fri, 1 Feb 2019 17:42:19 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Evan Green <evgreen@...omium.org>
CC:     <youlin.pei@...iatek.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Nicolas Boichat <drinkcat@...omium.org>,
        Arnd Bergmann <arnd@...db.de>, <srv_heupstream@...iatek.com>,
        Joerg Roedel <joro@...tes.org>,
        Will Deacon <will.deacon@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        Tomasz Figa <tfiga@...gle.com>,
        <iommu@...ts.linux-foundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        <linux-mediatek@...ts.infradead.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <yingjoe.chen@...iatek.com>, Robin Murphy <robin.murphy@....com>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v5 17/20] memory: mtk-smi: Get rid of need_larbid

On Thu, 2019-01-31 at 09:45 -0800, Evan Green wrote:
> On Wed, Jan 30, 2019 at 7:22 PM Yong Wu <yong.wu@...iatek.com> wrote:
> >
> > On Wed, 2019-01-30 at 11:11 -0800, Evan Green wrote:
> > > On Mon, Dec 31, 2018 at 7:59 PM Yong Wu <yong.wu@...iatek.com> wrote:
> > > >
> > > > The "mediatek,larb-id" has already been parsed in MTK IOMMU driver.
> > > > It's no need to parse it again in SMI driver. Only clean some codes.
> > > > This patch is fit for all the current mt2701, mt2712, mt7623, mt8173
> > > > and mt8183.
> > > >
> > > > After this patch, the "mediatek,larb-id" only be needed for mt2712
> > > > which have 2 M4Us. In the other SoCs, we can get the larb-id from M4U
> > > > in which the larbs in the "mediatek,larbs" always are ordered.
> > > >
> > > > CC: Matthias Brugger <matthias.bgg@...il.com>
> > > > Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> > > > ---
> > > >  drivers/memory/mtk-smi.c | 26 ++------------------------
> > > >  1 file changed, 2 insertions(+), 24 deletions(-)
> > > >
> > > > diff --git a/drivers/memory/mtk-smi.c b/drivers/memory/mtk-smi.c
> > > > index 08cf40d..10e6493 100644
> > > > --- a/drivers/memory/mtk-smi.c
> > > > +++ b/drivers/memory/mtk-smi.c
> > > > @@ -67,7 +67,6 @@ struct mtk_smi_common_plat {
> > > >  };
> > > >
> > > >  struct mtk_smi_larb_gen {
> > > > -       bool need_larbid;
> > > >         int port_in_larb[MTK_LARB_NR_MAX + 1];
> > > >         void (*config_port)(struct device *);
> > > >         unsigned int larb_direct_to_common_mask;
> > > > @@ -153,18 +152,9 @@ void mtk_smi_larb_put(struct device *larbdev)
> > > >         struct mtk_smi_iommu *smi_iommu = data;
> > > >         unsigned int         i;
> > > >
> > > > -       if (larb->larb_gen->need_larbid) {
> > > > -               larb->mmu = &smi_iommu->larb_imu[larb->larbid].mmu;
> > > > -               return 0;
> > > > -       }
> > > > -
> > > > -       /*
> > > > -        * If there is no larbid property, Loop to find the corresponding
> > > > -        * iommu information.
> > > > -        */
> > > > -       for (i = 0; i < smi_iommu->larb_nr; i++) {
> > > > +       for (i = 0; i < MTK_LARB_NR_MAX; i++) {
> > >
> > > Looks like this was the only use of mtk_smi_iommu.larb_nr. Should we
> > > remove that now?
> >
> > This is necessary since the mt2712 which has two M4U HW.
> >
> > From its dtsi[1], take iommu1 as a example, its larb_nr only is 3, but
> > we need scan all the larb.
> >
> > [1]
> > http://lists.infradead.org/pipermail/linux-mediatek/2018-December/016119.html
> 
> I'm not sure I follow. My point was that this structure member is only
> ever set but never read:
> $ git grep '[.>]larb_nr'
> drivers/iommu/mtk_iommu.c:      data->smi_imu.larb_nr = larb_nr;
> drivers/iommu/mtk_iommu_v1.c:   data->smi_imu.larb_nr = larb_nr;
> 
> Maybe I've applied the patches to the wrong tree, and there is a use
> of this member I'm not seeing?

Thanks. I misunderstood. It looks right, this variable can be deleted I
didn't realize this. Maybe I need use a new patch for this.

> -Evan