drm/exynos/fimd: add clock rate checking

In case of some platforms fimd clocks can be configured to
very low values, as a result refresh rate can be very low and
driver/drm-core will timeout waiting for vblanks, it will result
in premature removal of framebuffers and will cause oopses.
The patch adds atomic_check callback to fimd to prevent setting
such modes.

Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Signed-off-by: Andrzej Hajda <a.hajda@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 d472164..27efe30 100644 (file)
--- a/drivers/gpu/drm/exynos/exynos_drm_fimd.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
@@ -198,6 +198,7 @@ struct fimd_context {
        atomic_t                        wait_vsync_event;
        atomic_t                        win_updated;
        atomic_t                        triggering;
+       u32                             clkdiv;
 
        const struct fimd_driver_data *driver_data;
        struct drm_encoder *encoder;
@@ -389,15 +390,18 @@ static void fimd_clear_channels(struct exynos_drm_crtc *crtc)
        pm_runtime_put(ctx->dev);
 }
 
-static u32 fimd_calc_clkdiv(struct fimd_context *ctx,
-               const struct drm_display_mode *mode)
+
+static int fimd_atomic_check(struct exynos_drm_crtc *crtc,
+               struct drm_crtc_state *state)
 {
-       unsigned long ideal_clk;
+       struct drm_display_mode *mode = &state->adjusted_mode;
+       struct fimd_context *ctx = crtc->ctx;
+       unsigned long ideal_clk, lcd_rate;
        u32 clkdiv;
 
        if (mode->clock == 0) {
-               DRM_ERROR("Mode has zero clock value.\n");
-               return 0xff;
+               DRM_INFO("Mode has zero clock value.\n");
+               return -EINVAL;
        }
 
        ideal_clk = mode->clock * 1000;
@@ -410,10 +414,23 @@ static u32 fimd_calc_clkdiv(struct fimd_context *ctx,
                ideal_clk *= 2;
        }
 
+       lcd_rate = clk_get_rate(ctx->lcd_clk);
+       if (2 * lcd_rate < ideal_clk) {
+               DRM_INFO("sclk_fimd clock too low(%lu) for requested pixel clock(%lu)\n",
+                        lcd_rate, ideal_clk);
+               return -EINVAL;
+       }
+
        /* Find the clock divider value that gets us closest to ideal_clk */
-       clkdiv = DIV_ROUND_CLOSEST(clk_get_rate(ctx->lcd_clk), ideal_clk);
+       clkdiv = DIV_ROUND_CLOSEST(lcd_rate, ideal_clk);
+       if (clkdiv >= 0x200) {
+               DRM_INFO("requested pixel clock(%lu) too low\n", ideal_clk);
+               return -EINVAL;
+       }
+
+       ctx->clkdiv = (clkdiv < 0x100) ? clkdiv : 0xff;
 
-       return (clkdiv < 0x100) ? clkdiv : 0xff;
+       return 0;
 }
 
 static void fimd_setup_trigger(struct fimd_context *ctx)
@@ -442,7 +459,7 @@ static void fimd_commit(struct exynos_drm_crtc *crtc)
        struct drm_display_mode *mode = &crtc->base.state->adjusted_mode;
        const struct fimd_driver_data *driver_data = ctx->driver_data;
        void *timing_base = ctx->regs + driver_data->timing_base;
-       u32 val, clkdiv;
+       u32 val;
 
        if (ctx->suspended)
                return;
@@ -543,9 +560,8 @@ static void fimd_commit(struct exynos_drm_crtc *crtc)
        if (ctx->driver_data->has_clksel)
                val |= VIDCON0_CLKSEL_LCD;
 
-       clkdiv = fimd_calc_clkdiv(ctx, mode);
-       if (clkdiv > 1)
-               val |= VIDCON0_CLKVAL_F(clkdiv - 1) | VIDCON0_CLKDIR;
+       if (ctx->clkdiv > 1)
+               val |= VIDCON0_CLKVAL_F(ctx->clkdiv - 1) | VIDCON0_CLKDIR;
 
        writel(val, ctx->regs + VIDCON0);
 }
@@ -939,6 +955,7 @@ static const struct exynos_drm_crtc_ops fimd_crtc_ops = {
        .update_plane = fimd_update_plane,
        .disable_plane = fimd_disable_plane,
        .atomic_flush = fimd_atomic_flush,
+       .atomic_check = fimd_atomic_check,
        .te_handler = fimd_te_handler,
 };