drm/exynos: fimd: clear channel before enabling iommu

If any fimd channel was already active, initializing iommu will result
in a PAGE FAULT (e.g. u-boot could have turned on the display and
not disabled it before the kernel starts). This patch checks if any
channel is active before initializing iommu and disables it.

Signed-off-by: Akshu Agrawal <akshu.a@samsung.com>
Signed-off-by: Prathyush K <prathyush.k@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

diff --git a/drivers/gpu/drm/exynos/exynos_drm_fimd.c b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
index 97c61db..8ffbe2d 100644 (file)
--- a/drivers/gpu/drm/exynos/exynos_drm_fimd.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
@@ -695,6 +695,28 @@ out:
        return IRQ_HANDLED;
 }
 
+static void fimd_clear_channel(struct device *dev)
+{
+       struct fimd_context *ctx = get_fimd_context(dev);
+       int win, ch_enabled = 0;
+
+       DRM_DEBUG_KMS("%s\n", __FILE__);
+
+       /* Check if any channel is enabled */
+       for (win = 0; win < WINDOWS_NR; win++) {
+               u32 val = readl(ctx->regs + SHADOWCON);
+               if (val & SHADOWCON_CHx_ENABLE(win)) {
+                       val &= ~SHADOWCON_CHx_ENABLE(win);
+                       writel(val, ctx->regs + SHADOWCON);
+                       ch_enabled = 1;
+               }
+       }
+
+       /* Wait for vsync, as disable channel takes effect at next vsync */
+       if (ch_enabled)
+               fimd_wait_for_vblank(dev);
+}
+
 static int fimd_subdrv_probe(struct drm_device *drm_dev, struct device *dev)
 {
        DRM_DEBUG_KMS("%s\n", __FILE__);
@@ -717,9 +739,14 @@ static int fimd_subdrv_probe(struct drm_device *drm_dev, struct device *dev)
        drm_dev->vblank_disable_allowed = 1;
 
        /* attach this sub driver to iommu mapping if supported. */
-       if (is_drm_iommu_supported(drm_dev))
+       if (is_drm_iommu_supported(drm_dev)) {
+               /*
+                * If any channel is already active, iommu will throw
+                * a PAGE FAULT when enabled. So clear any channel if enabled.
+                */
+               fimd_clear_channel(dev);
                drm_iommu_attach_device(drm_dev, dev);
-
+       }
        return 0;
 }