drm/tegra: dc: Select root window for event dispatch

In finish pageflip, the driver was not selecting the root window when
dispatching events. This exposed a race where a plane update would
change the window selection and cause tegra_dc_finish_page_flip to check
the wrong base address.

This patch also protects access to the window selection register as well
as the registers affected by it.

Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

1 files changed, 22 insertions, 2 deletions

diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
index ef36f9d5e35e..978993fa3a36 100644
--- a/drivers/gpu/drm/tegra/dc.c
+++ b/drivers/gpu/drm/tegra/dc.c
@@ -168,7 +168,7 @@ static int tegra_dc_setup_window(struct tegra_dc *dc, unsigned int index,
                                  const struct tegra_dc_window *window)
 {
         unsigned h_offset, v_offset, h_size, v_size, h_dda, v_dda, bpp;
-        unsigned long value;
+        unsigned long value, flags;
         bool yuv, planar;
 
         /*
@@ -181,6 +181,8 @@ static int tegra_dc_setup_window(struct tegra_dc *dc, unsigned int index,
         else
                 bpp = planar ? 1 : 2;
 
+        spin_lock_irqsave(&dc->lock, flags);
+
         value = WINDOW_A_SELECT << index;
         tegra_dc_writel(dc, value, DC_CMD_DISPLAY_WINDOW_HEADER);
 
@@ -273,6 +275,7 @@ static int tegra_dc_setup_window(struct tegra_dc *dc, unsigned int index,
 
                 case TEGRA_BO_TILING_MODE_BLOCK:
                         DRM_ERROR("hardware doesn't support block linear mode\n");
+                        spin_unlock_irqrestore(&dc->lock, flags);
                         return -EINVAL;
                 }
 
@@ -331,6 +334,8 @@ static int tegra_dc_setup_window(struct tegra_dc *dc, unsigned int index,
 
         tegra_dc_window_commit(dc, index);
 
+        spin_unlock_irqrestore(&dc->lock, flags);
+
         return 0;
 }
 
@@ -338,11 +343,14 @@ static int tegra_window_plane_disable(struct drm_plane *plane)
 {
         struct tegra_dc *dc = to_tegra_dc(plane->crtc);
         struct tegra_plane *p = to_tegra_plane(plane);
+        unsigned long flags;
         u32 value;
 
         if (!plane->crtc)
                 return 0;
 
+        spin_lock_irqsave(&dc->lock, flags);
+
         value = WINDOW_A_SELECT << p->index;
         tegra_dc_writel(dc, value, DC_CMD_DISPLAY_WINDOW_HEADER);
 
@@ -352,6 +360,8 @@ static int tegra_window_plane_disable(struct drm_plane *plane)
 
         tegra_dc_window_commit(dc, p->index);
 
+        spin_unlock_irqrestore(&dc->lock, flags);
+
         return 0;
 }
 
@@ -699,14 +709,16 @@ static int tegra_dc_set_base(struct tegra_dc *dc, int x, int y,
         struct tegra_bo *bo = tegra_fb_get_plane(fb, 0);
         unsigned int h_offset = 0, v_offset = 0;
         struct tegra_bo_tiling tiling;
+        unsigned long value, flags;
         unsigned int format, swap;
-        unsigned long value;
         int err;
 
         err = tegra_fb_get_tiling(fb, &tiling);
         if (err < 0)
                 return err;
 
+        spin_lock_irqsave(&dc->lock, flags);
+
         tegra_dc_writel(dc, WINDOW_A_SELECT, DC_CMD_DISPLAY_WINDOW_HEADER);
 
         value = fb->offsets[0] + y * fb->pitches[0] +
@@ -752,6 +764,7 @@ static int tegra_dc_set_base(struct tegra_dc *dc, int x, int y,
 
                 case TEGRA_BO_TILING_MODE_BLOCK:
                         DRM_ERROR("hardware doesn't support block linear mode\n");
+                        spin_unlock_irqrestore(&dc->lock, flags);
                         return -EINVAL;
                 }
 
@@ -778,6 +791,8 @@ static int tegra_dc_set_base(struct tegra_dc *dc, int x, int y,
         tegra_dc_writel(dc, value << 8, DC_CMD_STATE_CONTROL);
         tegra_dc_writel(dc, value, DC_CMD_STATE_CONTROL);
 
+        spin_unlock_irqrestore(&dc->lock, flags);
+
         return 0;
 }
 
@@ -823,11 +838,16 @@ static void tegra_dc_finish_page_flip(struct tegra_dc *dc)
 
         bo = tegra_fb_get_plane(crtc->primary->fb, 0);
 
+        spin_lock_irqsave(&dc->lock, flags);
+
         /* check if new start address has been latched */
+        tegra_dc_writel(dc, WINDOW_A_SELECT, DC_CMD_DISPLAY_WINDOW_HEADER);
         tegra_dc_writel(dc, READ_MUX, DC_CMD_STATE_ACCESS);
         base = tegra_dc_readl(dc, DC_WINBUF_START_ADDR);
         tegra_dc_writel(dc, 0, DC_CMD_STATE_ACCESS);
 
+        spin_unlock_irqrestore(&dc->lock, flags);
+
         if (base == bo->paddr + crtc->primary->fb->offsets[0]) {
                 drm_crtc_send_vblank_event(crtc, dc->event);
                 drm_crtc_vblank_put(crtc);