Date:   Wed, 27 Feb 2019 22:34:43 +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>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        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 04/13] iommu/mediatek: Add device_link between the
 consumer and the larb devices

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:
> >
> > MediaTek IOMMU don't have its power-domain. all the consumer connect
> > with smi-larb, then connect with smi-common.
> >
> >         M4U
> >          |
> >     smi-common
> >          |
> >   -------------
> >   |         |    ...
> >   |         |
> > larb1     larb2
> >   |         |
> > vdec       venc
> >
> > When the consumer works, it should enable the smi-larb's power which
> > also need enable the smi-common's power firstly.
> >
> > Thus, First of all, use the device link connect the consumer and the
> > smi-larbs. then add device link between the smi-larb and smi-common.
> >
> > This patch adds device_link between the consumer and the larbs.
> >
> > Suggested-by: Tomasz Figa <tfiga@...omium.org>
> > Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> > ---
> >  drivers/iommu/mtk_iommu.c    | 15 +++++++++++++--
> >  drivers/iommu/mtk_iommu_v1.c | 14 ++++++++++++--
> >  2 files changed, 25 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> > index 202e41b..735ae8d 100644
> > --- a/drivers/iommu/mtk_iommu.c
> > +++ b/drivers/iommu/mtk_iommu.c
> > @@ -247,6 +247,7 @@ static void mtk_iommu_config(struct mtk_iommu_data *data,
> >         struct mtk_smi_larb_iommu    *larb_mmu;
> >         unsigned int                 larbid, portid;
> >         struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> > +       struct device_link *link;
> >         int i;
> >
> >         for (i = 0; i < fwspec->num_ids; ++i) {
> > @@ -257,10 +258,20 @@ static void mtk_iommu_config(struct mtk_iommu_data *data,
> >                 dev_dbg(dev, "%s iommu port: %d\n",
> >                         enable ? "enable" : "disable", portid);
> >
> > -               if (enable)
> > +               if (enable) {
> >                         larb_mmu->mmu |= MTK_SMI_MMU_EN(portid);
> > -               else
> > +                       /* Link the consumer with the larb device(supplier) */
> > +                       link = device_link_add(dev, larb_mmu->dev,
> > +                                              DL_FLAG_PM_RUNTIME |
> > +                                              DL_FLAG_AUTOREMOVE_CONSUMER);
> > +                       if (!link) {
> > +                               dev_err(dev, "Unable to link %s\n",
> > +                                       dev_name(larb_mmu->dev));
> > +                               return;
> 
> The return is a little odd here, given that you don't return an error
> and this function doesn't do anything else. If it's non-fatal that
> this link didn't get set up, then remove the return. If it is fatal,
> then return an error code.

I will remove the "return". Thanks.

> 
> > +                       }
> > +               } else {
> >                         larb_mmu->mmu &= ~MTK_SMI_MMU_EN(portid);
> > +               }
> >         }
> >  }
> >
> > diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c
> > index 9386aee..022bad9 100644
> > --- a/drivers/iommu/mtk_iommu_v1.c
> > +++ b/drivers/iommu/mtk_iommu_v1.c
> > @@ -201,6 +201,7 @@ static void mtk_iommu_config(struct mtk_iommu_data *data,
> >         struct mtk_smi_larb_iommu    *larb_mmu;
> >         unsigned int                 larbid, portid;
> >         struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> > +       struct device_link *link;
> >         int i;
> >
> >         for (i = 0; i < fwspec->num_ids; ++i) {
> > @@ -211,10 +212,19 @@ static void mtk_iommu_config(struct mtk_iommu_data *data,
> >                 dev_dbg(dev, "%s iommu port: %d\n",
> >                         enable ? "enable" : "disable", portid);
> >
> > -               if (enable)
> > +               if (enable) {
> >                         larb_mmu->mmu |= MTK_SMI_MMU_EN(portid);
> > -               else
> > +                       link = device_link_add(dev, larb_mmu->dev,
> > +                                              DL_FLAG_PM_RUNTIME |
> > +                                              DL_FLAG_AUTOREMOVE_CONSUMER);
> > +                       if (!link) {
> > +                               dev_err(dev, "Unable to link %s\n",
> > +                                       dev_name(larb_mmu->dev));
> > +                               return;
> 
> Same for this one.
> 
> > +                       }
> > +               } else {
> >                         larb_mmu->mmu &= ~MTK_SMI_MMU_EN(portid);
> > +               }
> >         }
> >  }
> >
> > --
> > 1.9.1
> >
> 
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