[RFC PATCH v5 6/6] drm: exynos: mixer: Add interconnect support

[Sylwester Nawrocki]

From: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>

This patch adds interconnect support to exynos-mixer. The mixer works
the same as before when CONFIG_INTERCONNECT is 'n'.

For proper operation of the video mixer block we need to ensure the
interconnect busses like DMC or LEFTBUS provide enough bandwidth so
as to avoid DMA buffer underruns in the mixer block. i.e we need to
prevent those busses from operating in low perfomance OPPs when
the mixer is running.
In this patch the bus bandwidth request is done through the interconnect
API, the bandiwidth value is calculated from selected DRM mode, i.e.
video plane width, height, refresh rate and pixel format.

Co-developed-by: Artur ÅwigoÅ <a.swigon@xxxxxxxxxxx>
Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
[s.nawrocki: renamed soc_path variable to icc_path, edited commit desc.]
Signed-off-by: Sylwester Nawrocki <s.nawrocki@xxxxxxxxxxx>
---
Changes for v5:
 - renamed soc_path variable to icc_path
---
 drivers/gpu/drm/exynos/exynos_mixer.c | 73 ++++++++++++++++++++++++++++++++---
 1 file changed, 68 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos_mixer.c b/drivers/gpu/drm/exynos/exynos_mixer.c
index 21b726b..bdae683 100644
--- a/drivers/gpu/drm/exynos/exynos_mixer.c
+++ b/drivers/gpu/drm/exynos/exynos_mixer.c
@@ -13,6 +13,7 @@
 #include <linux/component.h>
 #include <linux/delay.h>
 #include <linux/i2c.h>
+#include <linux/interconnect.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/kernel.h>
@@ -98,6 +99,7 @@ struct mixer_context {
 	struct exynos_drm_crtc	*crtc;
 	struct exynos_drm_plane	planes[MIXER_WIN_NR];
 	unsigned long		flags;
+	struct icc_path		*icc_path;
 
 	int			irq;
 	void __iomem		*mixer_regs;
@@ -934,6 +936,42 @@ static void mixer_disable_vblank(struct exynos_drm_crtc *crtc)
 	mixer_reg_writemask(mixer_ctx, MXR_INT_EN, 0, MXR_INT_EN_VSYNC);
 }
 
+static void mixer_set_memory_bandwidth(struct exynos_drm_crtc *crtc)
+{
+	struct drm_display_mode *mode = &crtc->base.state->adjusted_mode;
+	struct mixer_context *ctx = crtc->ctx;
+	unsigned long bw, bandwidth = 0;
+	u32 avg_bw, peak_bw;
+	int i, j, sub;
+
+	if (!ctx->icc_path)
+		return;
+
+	for (i = 0; i < MIXER_WIN_NR; i++) {
+		struct drm_plane *plane = &ctx->planes[i].base;
+		const struct drm_format_info *format;
+
+		if (plane->state && plane->state->crtc && plane->state->fb) {
+			format = plane->state->fb->format;
+			bw = mode->hdisplay * mode->vdisplay *
+							drm_mode_vrefresh(mode);
+			if (mode->flags & DRM_MODE_FLAG_INTERLACE)
+				bw /= 2;
+			for (j = 0; j < format->num_planes; j++) {
+				sub = j ? (format->vsub * format->hsub) : 1;
+				bandwidth += format->cpp[j] * bw / sub;
+			}
+		}
+	}
+
+	/* add 20% safety margin */
+	bandwidth = bandwidth / 4 * 5;
+	dev_dbg(ctx->dev, "exynos-mixer: safe bandwidth %ld Bps\n", bandwidth);
+
+	avg_bw = peak_bw = Bps_to_icc(bandwidth);
+	icc_set_bw(ctx->icc_path, avg_bw, peak_bw);
+}
+
 static void mixer_atomic_begin(struct exynos_drm_crtc *crtc)
 {
 	struct mixer_context *ctx = crtc->ctx;
@@ -985,6 +1023,7 @@ static void mixer_atomic_flush(struct exynos_drm_crtc *crtc)
 	if (!test_bit(MXR_BIT_POWERED, &mixer_ctx->flags))
 		return;
 
+	mixer_set_memory_bandwidth(crtc);
 	mixer_enable_sync(mixer_ctx);
 	exynos_crtc_handle_event(crtc);
 }
@@ -1032,6 +1071,7 @@ static void mixer_atomic_disable(struct exynos_drm_crtc *crtc)
 	for (i = 0; i < MIXER_WIN_NR; i++)
 		mixer_disable_plane(crtc, &ctx->planes[i]);
 
+	mixer_set_memory_bandwidth(crtc);
 	exynos_drm_pipe_clk_enable(crtc, false);
 
 	pm_runtime_put(ctx->dev);
@@ -1223,12 +1263,22 @@ static int mixer_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	const struct mixer_drv_data *drv;
 	struct mixer_context *ctx;
+	struct icc_path *path;
 	int ret;
 
+	/*
+	 * Returns NULL if CONFIG_INTERCONNECT is disabled.
+	 * May return ERR_PTR(-EPROBE_DEFER).
+	 */
+	path = of_icc_get(dev, NULL);
+	if (IS_ERR(path))
+		return PTR_ERR(path);
+
 	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
 	if (!ctx) {
 		DRM_DEV_ERROR(dev, "failed to alloc mixer context.\n");
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto err;
 	}
 
 	drv = of_device_get_match_data(dev);
@@ -1236,6 +1286,7 @@ static int mixer_probe(struct platform_device *pdev)
 	ctx->pdev = pdev;
 	ctx->dev = dev;
 	ctx->mxr_ver = drv->version;
+	ctx->icc_path = path;
 
 	if (drv->is_vp_enabled)
 		__set_bit(MXR_BIT_VP_ENABLED, &ctx->flags);
@@ -1245,17 +1296,29 @@ static int mixer_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, ctx);
 
 	ret = component_add(&pdev->dev, &mixer_component_ops);
-	if (!ret)
-		pm_runtime_enable(dev);
+	if (ret < 0)
+		goto err;
+
+	pm_runtime_enable(dev);
+
+	return 0;
+
+err:
+	icc_put(path);
 
 	return ret;
 }
 
 static int mixer_remove(struct platform_device *pdev)
 {
-	pm_runtime_disable(&pdev->dev);
+	struct device *dev = &pdev->dev;
+	struct mixer_context *ctx = dev_get_drvdata(dev);
+
+	pm_runtime_disable(dev);
+
+	component_del(dev, &mixer_component_ops);
 
-	component_del(&pdev->dev, &mixer_component_ops);
+	icc_put(ctx->icc_path);
 
 	return 0;
 }
-- 
2.7.4