The sequence for replacing the scanout buffer is much shorter than a
full mode change operation so implementing this callback considerably
speeds up cases where only a new framebuffer is to be scanned out.

Signed-off-by: Thierry Reding <thierry.reding at avionic-design.de>
---
Changes in v3:
- split DC_CMD_STATE_CONTROL writes

 drivers/gpu/drm/tegra/dc.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
index 8f97b1c..cc4c85e 100644
--- a/drivers/gpu/drm/tegra/dc.c
+++ b/drivers/gpu/drm/tegra/dc.c
@@ -114,6 +114,27 @@ static int tegra_dc_add_planes(struct drm_device *drm, 
struct tegra_dc *dc)
        return 0;
 }

+static int tegra_dc_set_base(struct tegra_dc *dc, int x, int y,
+                            struct tegra_framebuffer *fb)
+{
+       unsigned long value;
+
+       tegra_dc_writel(dc, WINDOW_A_SELECT, DC_CMD_DISPLAY_WINDOW_HEADER);
+
+       value = fb->base.offsets[0] + y * fb->base.pitches[0] +
+               x * fb->base.bits_per_pixel / 8;
+
+       tegra_dc_writel(dc, fb->obj->paddr + value, DC_WINBUF_START_ADDR);
+
+       value = GENERAL_UPDATE | WIN_A_UPDATE;
+       tegra_dc_writel(dc, value, DC_CMD_STATE_CONTROL);
+
+       value = GENERAL_ACT_REQ | WIN_A_ACT_REQ;
+       tegra_dc_writel(dc, value, DC_CMD_STATE_CONTROL);
+
+       return 0;
+}
+
 static const struct drm_crtc_funcs tegra_crtc_funcs = {
        .set_config = drm_crtc_helper_set_config,
        .destroy = drm_crtc_cleanup,
@@ -416,6 +437,15 @@ static int tegra_crtc_mode_set(struct drm_crtc *crtc,
        return 0;
 }

+static int tegra_crtc_mode_set_base(struct drm_crtc *crtc, int x, int y,
+                                   struct drm_framebuffer *old_fb)
+{
+       struct tegra_framebuffer *fb = to_tegra_fb(crtc->fb);
+       struct tegra_dc *dc = to_tegra_dc(crtc);
+
+       return tegra_dc_set_base(dc, x, y, fb);
+}
+
 static void tegra_crtc_prepare(struct drm_crtc *crtc)
 {
        struct tegra_dc *dc = to_tegra_dc(crtc);
@@ -495,6 +525,7 @@ static const struct drm_crtc_helper_funcs 
tegra_crtc_helper_funcs = {
        .disable = tegra_crtc_disable,
        .mode_fixup = tegra_crtc_mode_fixup,
        .mode_set = tegra_crtc_mode_set,
+       .mode_set_base = tegra_crtc_mode_set_base,
        .prepare = tegra_crtc_prepare,
        .commit = tegra_crtc_commit,
        .load_lut = tegra_crtc_load_lut,
-- 
1.8.1.2

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