[PATCH 4.13 031/110] drm/exynos: Fix locking in the suspend/resume paths

[Greg Kroah-Hartman]

4.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marek Szyprowski <m.szyprow...@samsung.com>

commit 5baf6bb0fd2388742a0846cc7bcacee6dec78235 upstream.

Commit 48a92916729b ("drm/exynos: use drm_for_each_connector_iter()")
replaced unsafe drm_for_each_connector() with drm_for_each_connector_iter()
and removed surrounding drm_modeset_lock calls. However, that lock was
there not only to protect unsafe drm_for_each_connector(), but it was also
required to be held by the dpms code which was called from the loop body.
This patch restores those drm_modeset_lock calls to fix broken suspend
and resume of Exynos DRM subsystem in v4.13 kernel.

Fixes: 48a92916729b ("drm/exynos: use drm_for_each_connector_iter()")
Signed-off-by: Marek Szyprowski <m.szyprow...@samsung.com>
Acked-by: Krzysztof Kozlowski <k...@kernel.org>
Signed-off-by: Inki Dae <inki....@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/gpu/drm/exynos/exynos_drm_drv.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/gpu/drm/exynos/exynos_drm_drv.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_drv.c
@@ -176,6 +176,7 @@ static int exynos_drm_suspend(struct dev
        if (pm_runtime_suspended(dev) || !drm_dev)
                return 0;
 
+       drm_modeset_lock_all(drm_dev);
        drm_connector_list_iter_begin(drm_dev, &conn_iter);
        drm_for_each_connector_iter(connector, &conn_iter) {
                int old_dpms = connector->dpms;
@@ -187,6 +188,7 @@ static int exynos_drm_suspend(struct dev
                connector->dpms = old_dpms;
        }
        drm_connector_list_iter_end(&conn_iter);
+       drm_modeset_unlock_all(drm_dev);
 
        return 0;
 }
@@ -200,6 +202,7 @@ static int exynos_drm_resume(struct devi
        if (pm_runtime_suspended(dev) || !drm_dev)
                return 0;
 
+       drm_modeset_lock_all(drm_dev);
        drm_connector_list_iter_begin(drm_dev, &conn_iter);
        drm_for_each_connector_iter(connector, &conn_iter) {
                if (connector->funcs->dpms) {
@@ -210,6 +213,7 @@ static int exynos_drm_resume(struct devi
                }
        }
        drm_connector_list_iter_end(&conn_iter);
+       drm_modeset_unlock_all(drm_dev);
 
        return 0;
 }