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SubjectRe: [PATCH v1 1/5] drm/tegra: dc: Balance IOMMU group refcounting
On Fri, May 04, 2018 at 02:47:19AM +0300, Dmitry Osipenko wrote:
> Remove unneeded iommu_group_get() and add missing iommu_group_put(),
> correcting IOMMU group refcount. This is a minor correction / cleanup that
> doesn't really fix anything because Tegra's IOMMU driver are built-in and
> hence groups refcounting can't hold IOMMU driver from unloading.
>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
> drivers/gpu/drm/tegra/dc.c | 35 +++++++++++++++++------------------
> drivers/gpu/drm/tegra/dc.h | 2 +-
> drivers/gpu/drm/tegra/drm.h | 2 +-
> 3 files changed, 19 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
> index d7a0f62c6e2e..9fc34c6a7218 100644
> --- a/drivers/gpu/drm/tegra/dc.c
> +++ b/drivers/gpu/drm/tegra/dc.c
> @@ -1927,7 +1927,6 @@ static irqreturn_t tegra_dc_irq(int irq, void *data)
> static int tegra_dc_init(struct host1x_client *client)
> {
> struct drm_device *drm = dev_get_drvdata(client->parent);
> - struct iommu_group *group = iommu_group_get(client->dev);
> unsigned long flags = HOST1X_SYNCPT_CLIENT_MANAGED;
> struct tegra_dc *dc = host1x_client_to_dc(client);
> struct tegra_drm *tegra = drm->dev_private;
> @@ -1939,20 +1938,21 @@ static int tegra_dc_init(struct host1x_client *client)
> if (!dc->syncpt)
> dev_warn(dc->dev, "failed to allocate syncpoint\n");
>
> - if (group && tegra->domain) {
> - if (group != tegra->group) {
> - err = iommu_attach_group(tegra->domain, group);
> + if (tegra->domain) {
> + dc->group = iommu_group_get(client->dev);
> +
> + if (dc->group && dc->group != tegra->dc_group) {
> + err = iommu_attach_group(tegra->domain, dc->group);
> if (err < 0) {
> dev_err(dc->dev,
> "failed to attach to domain: %d\n",
> err);
> + iommu_group_put(dc->group);
> return err;
> }
>
> - tegra->group = group;
> + tegra->dc_group = dc->group;
> }
> -
> - dc->domain = tegra->domain;
> }
>
> if (dc->soc->wgrps)
> @@ -2017,13 +2017,13 @@ static int tegra_dc_init(struct host1x_client *client)
> if (!IS_ERR(primary))
> drm_plane_cleanup(primary);
>
> - if (group && dc->domain) {
> - if (group == tegra->group) {
> - iommu_detach_group(dc->domain, group);
> - tegra->group = NULL;
> + if (dc->group) {
> + if (dc->group && dc->group == tegra->dc_group) {

You can drop the dc->group check from the second conditional.

> + iommu_detach_group(tegra->domain, dc->group);
> + tegra->dc_group = NULL;
> }
>
> - dc->domain = NULL;
> + iommu_group_put(dc->group);
> }
>
> return err;
> @@ -2032,7 +2032,6 @@ static int tegra_dc_init(struct host1x_client *client)
> static int tegra_dc_exit(struct host1x_client *client)
> {
> struct drm_device *drm = dev_get_drvdata(client->parent);
> - struct iommu_group *group = iommu_group_get(client->dev);
> struct tegra_dc *dc = host1x_client_to_dc(client);
> struct tegra_drm *tegra = drm->dev_private;
> int err;
> @@ -2045,13 +2044,13 @@ static int tegra_dc_exit(struct host1x_client *client)
> return err;
> }
>
> - if (group && dc->domain) {
> - if (group == tegra->group) {
> - iommu_detach_group(dc->domain, group);
> - tegra->group = NULL;
> + if (dc->group) {
> + if (dc->group && dc->group == tegra->dc_group) {
> + iommu_detach_group(tegra->domain, dc->group);
> + tegra->dc_group = NULL;
> }
>
> - dc->domain = NULL;
> + iommu_group_put(dc->group);
> }
>
> host1x_syncpt_free(dc->syncpt);
> diff --git a/drivers/gpu/drm/tegra/dc.h b/drivers/gpu/drm/tegra/dc.h
> index ca5cac6bf8ea..5ca4e07333bb 100644
> --- a/drivers/gpu/drm/tegra/dc.h
> +++ b/drivers/gpu/drm/tegra/dc.h
> @@ -94,7 +94,7 @@ struct tegra_dc {
>
> const struct tegra_dc_soc_info *soc;
>
> - struct iommu_domain *domain;
> + struct iommu_group *group;
> };
>
> static inline struct tegra_dc *
> diff --git a/drivers/gpu/drm/tegra/drm.h b/drivers/gpu/drm/tegra/drm.h
> index 4f41aaec8530..7777640a6911 100644
> --- a/drivers/gpu/drm/tegra/drm.h
> +++ b/drivers/gpu/drm/tegra/drm.h
> @@ -46,7 +46,7 @@ struct tegra_drm {
> struct drm_device *drm;
>
> struct iommu_domain *domain;
> - struct iommu_group *group;
> + struct iommu_group *dc_group;

It's not obvious to me why this needs to be renamed.

Thierry
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