[PATCH 3/6] drm: tegra: protect DC register access with mutex

[Lucas Stach]

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 at lynxeye.de>
---
We could probably make this a bit more fine grained, but this would add
some complexity and I don't really see a win there for now.
---
 drivers/gpu/drm/tegra/dc.c  | 13 +++++++++++++
 drivers/gpu/drm/tegra/drm.h |  1 +
 2 Dateien ge?ndert, 14 Zeilen hinzugef?gt(+)

diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
index 54683e4..b256574 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 3a843a7..eae1f56 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;

-- 
1.7.11.7