drm: exynos: dsi: Add atomic_get_input_bus_fmts

Finding the right input bus format throughout the pipeline is hard
so add atomic_get_input_bus_fmts callback and initialize with the
proper input format from list of supported output formats.

This format can be used in pipeline for negotiating bus format between
the DSI-end of this bridge and the other component closer to pipeline
components.

List of Pixel formats are taken from,
AN13573 i.MX 8/RT MIPI DSI/CSI-2, Rev. 0, 21 March 2022
3.7.4 Pixel formats
Table 14. DSI pixel packing formats
Reviewed-by: Marek Vasut <marex@denx.de>
Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_dsi.c

@@ -12,6 +12,7 @@
 #include <linux/component.h>
 #include <linux/gpio/consumer.h>
 #include <linux/irq.h>
+#include <linux/media-bus-format.h>
 #include <linux/of_device.h>
 #include <linux/of_graph.h>
 #include <linux/phy/phy.h>
@@ -1466,6 +1467,66 @@ static void exynos_dsi_atomic_post_disable(struct drm_bridge *bridge,
 	pm_runtime_put_sync(dsi->dev);
 }
 
+/*
+ * This pixel output formats list referenced from,
+ * AN13573 i.MX 8/RT MIPI DSI/CSI-2, Rev. 0, 21 March 2022
+ * 3.7.4 Pixel formats
+ * Table 14. DSI pixel packing formats
+ */
+static const u32 exynos_dsi_pixel_output_fmts[] = {
+	MEDIA_BUS_FMT_YUYV10_1X20,
+	MEDIA_BUS_FMT_YUYV12_1X24,
+	MEDIA_BUS_FMT_UYVY8_1X16,
+	MEDIA_BUS_FMT_RGB101010_1X30,
+	MEDIA_BUS_FMT_RGB121212_1X36,
+	MEDIA_BUS_FMT_RGB565_1X16,
+	MEDIA_BUS_FMT_RGB666_1X18,
+	MEDIA_BUS_FMT_RGB888_1X24,
+};
+
+static bool exynos_dsi_pixel_output_fmt_supported(u32 fmt)
+{
+	int i;
+
+	if (fmt == MEDIA_BUS_FMT_FIXED)
+		return false;
+
+	for (i = 0; i < ARRAY_SIZE(exynos_dsi_pixel_output_fmts); i++) {
+		if (exynos_dsi_pixel_output_fmts[i] == fmt)
+			return true;
+	}
+
+	return false;
+}
+
+static u32 *
+exynos_dsi_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
+				     struct drm_bridge_state *bridge_state,
+				     struct drm_crtc_state *crtc_state,
+				     struct drm_connector_state *conn_state,
+				     u32 output_fmt,
+				     unsigned int *num_input_fmts)
+{
+	u32 *input_fmts;
+
+	input_fmts = kmalloc(sizeof(*input_fmts), GFP_KERNEL);
+	if (!input_fmts)
+		return NULL;
+
+	if (!exynos_dsi_pixel_output_fmt_supported(output_fmt))
+		/*
+		 * Some bridge/display drivers are still not able to pass the
+		 * correct format, so handle those pipelines by falling back
+		 * to the default format till the supported formats finalized.
+		 */
+		output_fmt = MEDIA_BUS_FMT_RGB888_1X24;
+
+	input_fmts[0] = output_fmt;
+	*num_input_fmts = 1;
+
+	return input_fmts;
+}
+
 static int exynos_dsi_atomic_check(struct drm_bridge *bridge,
 				   struct drm_bridge_state *bridge_state,
 				   struct drm_crtc_state *crtc_state,
@@ -1514,6 +1575,7 @@ static const struct drm_bridge_funcs exynos_dsi_bridge_funcs = {
 	.atomic_duplicate_state		= drm_atomic_helper_bridge_duplicate_state,
 	.atomic_destroy_state		= drm_atomic_helper_bridge_destroy_state,
 	.atomic_reset			= drm_atomic_helper_bridge_reset,
+	.atomic_get_input_bus_fmts	= exynos_dsi_atomic_get_input_bus_fmts,
 	.atomic_check			= exynos_dsi_atomic_check,
 	.atomic_pre_enable		= exynos_dsi_atomic_pre_enable,
 	.atomic_enable			= exynos_dsi_atomic_enable,