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

Nicolas Boichat
2020-03-05T05:21:52Z

On Tue, Sep 3, 2019 at 5:38 PM Yong Wu <yong.wu@mediatek.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.
>
> 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@chromium.org>
> Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> ---
> 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
>