Re: [PATCH v6 03/11] iommu/mediatek: Add device_link between the consumer and the larb devices

Dafna Hirschfeld
2021-07-14T08:28:12Z

On 14.07.21 04:56, Yong Wu wrote:
> MediaTek IOMMU-SMI diagram is like below. 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] https://lore.kernel.org/linux-mediatek/1564213888.22908.4.camel@mhfsdcap03/
> [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 | 22 ++++++++++++++++++++++
> drivers/iommu/mtk_iommu_v1.c | 20 +++++++++++++++++++-
> 2 files changed, 41 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> index a02dde094788..ee742900cf4b 100644
> --- a/drivers/iommu/mtk_iommu.c
> +++ b/drivers/iommu/mtk_iommu.c
> @@ -571,22 +571,44 @@ static struct iommu_device *mtk_iommu_probe_device(struct device *dev)
> {
> struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> struct mtk_iommu_data *data;
> + struct device_link *link;
> + struct device *larbdev;
> + unsigned int larbid;
>
> if (!fwspec || fwspec->ops != &mtk_iommu_ops)
> return ERR_PTR(-ENODEV); /* Not a iommu client device */
>
> data = dev_iommu_priv_get(dev);
>
> + /*
> + * Link the consumer device with the smi-larb device(supplier)
> + * The device in each a larb is a independent HW. thus only link
> + * one larb here.
> + */
> + larbid = MTK_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));
shoudn't ERR_PTR be returned in case of failure?

Thanks,
Dafna

> return &data->iommu;
> }
>
> static void mtk_iommu_release_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;
>
> + data = dev_iommu_priv_get(dev);
> + larbid = MTK_M4U_TO_LARB(fwspec->ids[0]);
> + larbdev = data->larb_imu[larbid].dev;
> + device_link_remove(dev, larbdev);
> +
> iommu_fwspec_free(dev);
> }
>
> diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c
> index d9365a3d8dc9..d2a7c66b8239 100644
> --- a/drivers/iommu/mtk_iommu_v1.c
> +++ b/drivers/iommu/mtk_iommu_v1.c
> @@ -424,7 +424,9 @@ static struct iommu_device *mtk_iommu_probe_device(struct device *dev)
> struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> struct of_phandle_args iommu_spec;
> struct mtk_iommu_data *data;
> - int err, idx = 0;
> + int err, idx = 0, larbid;
> + struct device_link *link;
> + struct device *larbdev;
>
> while (!of_parse_phandle_with_args(dev->of_node, "iommus",
> "#iommu-cells",
> @@ -445,6 +447,14 @@ static struct iommu_device *mtk_iommu_probe_device(struct device *dev)
>
> data = dev_iommu_priv_get(dev);
>
> + /* 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 &data->iommu;
> }
>
> @@ -465,10 +475,18 @@ static void mtk_iommu_probe_finalize(struct device *dev)
> static void mtk_iommu_release_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;
>
> + data = dev_iommu_priv_get(dev);
> + larbid = mt2701_m4u_to_larb(fwspec->ids[0]);
> + larbdev = data->larb_imu[larbid].dev;
> + device_link_remove(dev, larbdev);
> +
> iommu_fwspec_free(dev);
> }