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

[Nicolas Boichat]

On Tue, Sep 3, 2019 at 5:38 PM Yong Wu <yong.wu@xxxxxxxxxxxx> 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 <tfiga@xxxxxxxxxxxx>
> Signed-off-by: Yong Wu <yong.wu@xxxxxxxxxxxx>
> ---
>  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?

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

> +       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
>