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Subject: Re: [PATCH v3 03/14] iommu/mediatek: Add device_link between the consumer and the larb devices

On Thu, 2020-03-05 at 13:14 +0800, Nicolas Boichat wrote:
> On Tue, Sep 3, 2019 at 5:38 PM Yong Wu <[email protected]> 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.
> >
> > When device_link_add, I add the flag DL_FLAG_STATELESS to avoid calling
> > pm_runtime_xx to keep the original status of clocks. It can avoid two
> > issues:
> > 1) Display HW show fastlogo abnormally reported in [1]. At the beggining,
> > all the clocks are enabled before entering kernel, but the clocks for
> > display HW(always in larb0) will be gated after clk_enable and clk_disable
> > called from device_link_add(->pm_runtime_resume) and rpm_idle. The clock
> > operation happened before display driver probe. At that time, the display
> > HW will be abnormal.
> >
> > 2) A deadlock issue reported in [2]. Use DL_FLAG_STATELESS to skip
> > pm_runtime_xx to avoid the deadlock.
> >
> > Corresponding, DL_FLAG_AUTOREMOVE_CONSUMER can't be added, then
> > device_link_removed should be added explicitly.
> >
> > [1] http://lists.infradead.org/pipermail/linux-mediatek/2019-July/
> > 021500.html
> > [2] https://lore.kernel.org/patchwork/patch/1086569/
> >
> > Suggested-by: Tomasz Figa <[email protected]>
> > Signed-off-by: Yong Wu <[email protected]>
> > ---
> > drivers/iommu/mtk_iommu.c | 17 +++++++++++++++++
> > drivers/iommu/mtk_iommu_v1.c | 18 +++++++++++++++++-
> > 2 files changed, 34 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> > index b138b94..2511b3c 100644
> > --- a/drivers/iommu/mtk_iommu.c
> > +++ b/drivers/iommu/mtk_iommu.c
> > @@ -450,6 +450,9 @@ static int mtk_iommu_add_device(struct device *dev)
> > struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> > struct mtk_iommu_data *data;
> > struct iommu_group *group;
> > + struct device_link *link;
> > + struct device *larbdev;
> > + unsigned int larbid;
> >
> > if (!fwspec || fwspec->ops != &mtk_iommu_ops)
> > return -ENODEV; /* Not a iommu client device */
> > @@ -461,6 +464,14 @@ static int mtk_iommu_add_device(struct device *dev)
> > if (IS_ERR(group))
> > return PTR_ERR(group);
> >
> > + /* Link the consumer device with the smi-larb device(supplier) */
> > + larbid = MTK_M4U_TO_LARB(fwspec->ids[0]);
>
> I'll mirror the comment I made on gerrit
> (https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/1361013):
> Maybe I'm missing something here, but for example, on MT8173,
> vcodec_enc: vcodec@18002000 needs to use both larb3 and larb5, isn't
> the code below just adding a link for larb3?

Yes. It only add larb3 here.

>
> Do we need to iterate over all fwspecs->ids to figure out which larbs
> we need to add links to each of them?

We have checked this venc issue. Currently I have requested our venc guy
to seperate larb3-venc and larb5-venc in the driver[1] since they are
independent HW actually. I will put it into this series when I send next
version.

If there is some reasonable driver which have two larbs in it, then the
iterating is really necessary, But I don't see it right now. Only using
fwspec->ids[0] is enough for now.

[1]
https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/1958322

>
> > + larbdev = data->larb_imu[larbid].dev;
> > + link = device_link_add(dev, larbdev,
> > + DL_FLAG_PM_RUNTIME | DL_FLAG_STATELESS);
> > + if (!link)
> > + dev_err(dev, "Unable to link %s\n", dev_name(larbdev));
> > +
> > iommu_group_put(group);
> > return 0;
> > }
> > @@ -469,6 +480,8 @@ static void mtk_iommu_remove_device(struct device *dev)
> > {
> > struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> > struct mtk_iommu_data *data;
> > + struct device *larbdev;
> > + unsigned int larbid;
> >
> > if (!fwspec || fwspec->ops != &mtk_iommu_ops)
> > return;
> > @@ -476,6 +489,10 @@ static void mtk_iommu_remove_device(struct device *dev)
> > data = fwspec->iommu_priv;
> > iommu_device_unlink(&data->iommu, dev);
> >
> > + larbid = MTK_M4U_TO_LARB(fwspec->ids[0]);
> > + larbdev = data->larb_imu[larbid].dev;
> > + device_link_remove(dev, larbdev);
> > +
> > iommu_group_remove_device(dev);
> > iommu_fwspec_free(dev);
> > }
> > diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c
> > index 2034d72..a7f22a2 100644
> > --- a/drivers/iommu/mtk_iommu_v1.c
> > +++ b/drivers/iommu/mtk_iommu_v1.c
> > @@ -423,7 +423,9 @@ static int mtk_iommu_add_device(struct device *dev)
> > struct of_phandle_iterator it;
> > struct mtk_iommu_data *data;
> > struct iommu_group *group;
> > - int err;
> > + struct device_link *link;
> > + struct device *larbdev;
> > + int err, larbid;
> >
> > of_for_each_phandle(&it, err, dev->of_node, "iommus",
> > "#iommu-cells", 0) {
> > @@ -466,6 +468,14 @@ static int mtk_iommu_add_device(struct device *dev)
> > return err;
> > }
> >
> > + /* Link the consumer device with the smi-larb device(supplier) */
> > + larbid = mt2701_m4u_to_larb(fwspec->ids[0]);
> > + larbdev = data->larb_imu[larbid].dev;
> > + link = device_link_add(dev, larbdev,
> > + DL_FLAG_PM_RUNTIME | DL_FLAG_STATELESS);
> > + if (!link)
> > + dev_err(dev, "Unable to link %s\n", dev_name(larbdev));
> > +
> > return iommu_device_link(&data->iommu, dev);
> > }
> >
> > @@ -473,6 +483,8 @@ static void mtk_iommu_remove_device(struct device *dev)
> > {
> > struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> > struct mtk_iommu_data *data;
> > + struct device *larbdev;
> > + unsigned int larbid;
> >
> > if (!fwspec || fwspec->ops != &mtk_iommu_ops)
> > return;
> > @@ -480,6 +492,10 @@ static void mtk_iommu_remove_device(struct device *dev)
> > data = fwspec->iommu_priv;
> > iommu_device_unlink(&data->iommu, dev);
> >
> > + larbid = mt2701_m4u_to_larb(fwspec->ids[0]);
> > + larbdev = data->larb_imu[larbid].dev;
> > + device_link_remove(dev, larbdev);
> > +
> > iommu_group_remove_device(dev);
> > iommu_fwspec_free(dev);
> > }
> > --
> > 1.9.1
> >