drm: tegra: protect DC register access with mutex

Window properties are programmed through a shared aperture and have to
happen atomically. Also we do the read-update-write dance on some of the
shared regs.
To make sure that different functions don't stumble over each other
protect the register access with a mutex.

Signed-off-by: Lucas Stach <dev@lynxeye.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>

2 files changed, 14 insertions, 0 deletions

diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
index 54683e430c77..b256574409e7 100644
--- a/drivers/gpu/drm/tegra/dc.c
+++ b/drivers/gpu/drm/tegra/dc.c
@@ -171,6 +171,8 @@ static int tegra_crtc_mode_set(struct drm_crtc *crtc,
                 return err;
         }
 
+        mutex_lock(&dc->regs_mutex);
+
         /* program display mode */
         tegra_dc_set_timings(dc, mode);
 
@@ -269,6 +271,8 @@ static int tegra_crtc_mode_set(struct drm_crtc *crtc,
         tegra_dc_writel(dc, 0xff00, DC_WIN_BLEND_NOKEY);
         tegra_dc_writel(dc, 0xff00, DC_WIN_BLEND_1WIN);
 
+        mutex_unlock(&dc->regs_mutex);
+
         return 0;
 }
 
@@ -287,6 +291,8 @@ static void tegra_crtc_prepare(struct drm_crtc *crtc)
         else
                 syncpt = SYNCPT_VBLANK0;
 
+        mutex_lock(&dc->regs_mutex);
+
         /* initialize display controller */
         tegra_dc_writel(dc, 0x00000100, DC_CMD_GENERAL_INCR_SYNCPT_CNTRL);
         tegra_dc_writel(dc, 0x100 | syncpt, DC_CMD_CONT_SYNCPT_VSYNC);
@@ -320,6 +326,8 @@ static void tegra_crtc_prepare(struct drm_crtc *crtc)
 
         value = VBLANK_INT | WIN_A_UF_INT | WIN_B_UF_INT | WIN_C_UF_INT;
         tegra_dc_writel(dc, value, DC_CMD_INT_ENABLE);
+
+        mutex_unlock(&dc->regs_mutex);
 }
 
 static void tegra_crtc_commit(struct drm_crtc *crtc)
@@ -330,6 +338,8 @@ static void tegra_crtc_commit(struct drm_crtc *crtc)
 
         update_mask = GENERAL_ACT_REQ | WIN_A_ACT_REQ;
 
+        mutex_lock(&dc->regs_mutex);
+
         tegra_dc_writel(dc, update_mask << 8, DC_CMD_STATE_CONTROL);
 
         value = tegra_dc_readl(dc, DC_CMD_INT_ENABLE);
@@ -341,6 +351,8 @@ static void tegra_crtc_commit(struct drm_crtc *crtc)
         tegra_dc_writel(dc, value, DC_CMD_INT_MASK);
 
         tegra_dc_writel(dc, update_mask, DC_CMD_STATE_CONTROL);
+
+        mutex_unlock(&dc->regs_mutex);
 }
 
 static void tegra_crtc_load_lut(struct drm_crtc *crtc)
@@ -747,6 +759,7 @@ static int tegra_dc_probe(struct platform_device *pdev)
                 return -ENOMEM;
 
         INIT_LIST_HEAD(&dc->list);
+        mutex_init(&dc->regs_mutex);
         dc->dev = &pdev->dev;
 
         dc->clk = devm_clk_get(&pdev->dev, NULL);
diff --git a/drivers/gpu/drm/tegra/drm.h b/drivers/gpu/drm/tegra/drm.h
index 3a843a77ddc7..eae1f564b716 100644
--- a/drivers/gpu/drm/tegra/drm.h
+++ b/drivers/gpu/drm/tegra/drm.h
@@ -84,6 +84,7 @@ struct tegra_dc {
 
         struct clk *clk;
 
+        struct mutex regs_mutex;
         void __iomem *regs;
         int irq;