[PATCH v2 11/17] drm/spacemit: add Saturn DPU DRM device driver

[Cody Kang via B4 Relay <devnull+codykang.hk.gmail.com@kernel.org>]

From: Cody Kang <codykang.hk@gmail.com>

Add the DRM device for the SpacemiT K3 Saturn display processing unit
and hook the driver up to the build. The SoC has two DPU instances;
each drives one CRTC that scans out a single primary plane in linear
RGB at up to 3840x2160@60 and feeds a downstream DP/eDP controller
over an OF-graph endpoint. Buffers use drm_gem_shmem_helper. The
AFBC/compressed decode path is not exposed and writeback is not
implemented.

Signed-off-by: Cody Kang <codykang.hk@gmail.com>

---
v2:
- check for an ERR_PTR component match before
  component_master_add_with_match() (Sashiko)
- add a comment explaining why commit_tail waits for flip_done before
  commit_hw_done (Sashiko)
---
 drivers/gpu/drm/Kconfig                 |   1 +
 drivers/gpu/drm/Makefile                |   1 +
 drivers/gpu/drm/spacemit/Kconfig        |  18 ++++
 drivers/gpu/drm/spacemit/Makefile       |  12 +++
 drivers/gpu/drm/spacemit/spacemit_drm.c | 140 ++++++++++++++++++++++++++++++++
 5 files changed, 172 insertions(+)

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 323422861e8f6..81081562a6da2 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -341,6 +341,7 @@ source "drivers/gpu/drm/renesas/Kconfig"
 source "drivers/gpu/drm/rockchip/Kconfig"
 source "drivers/gpu/drm/sitronix/Kconfig"
 source "drivers/gpu/drm/solomon/Kconfig"
+source "drivers/gpu/drm/spacemit/Kconfig"
 source "drivers/gpu/drm/sprd/Kconfig"
 source "drivers/gpu/drm/sti/Kconfig"
 source "drivers/gpu/drm/stm/Kconfig"
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index e97faabcd7830..4a105520ee912 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -204,6 +204,7 @@ obj-$(CONFIG_DRM_MSM) += msm/
 obj-$(CONFIG_DRM_TEGRA) += tegra/
 obj-$(CONFIG_DRM_STM) += stm/
 obj-$(CONFIG_DRM_STI) += sti/
+obj-$(CONFIG_DRM_SPACEMIT) += spacemit/
 obj-y 			+= imx/
 obj-$(CONFIG_DRM_INGENIC) += ingenic/
 obj-$(CONFIG_DRM_LOGICVC) += logicvc/
diff --git a/drivers/gpu/drm/spacemit/Kconfig b/drivers/gpu/drm/spacemit/Kconfig
new file mode 100644
index 0000000000000..51e38dabfdba5
--- /dev/null
+++ b/drivers/gpu/drm/spacemit/Kconfig
@@ -0,0 +1,18 @@
+# SPDX-License-Identifier: GPL-2.0
+
+config DRM_SPACEMIT
+	tristate "DRM support for SpacemiT display controllers"
+	depends on DRM && OF && MMU
+	depends on ARCH_SPACEMIT || COMPILE_TEST
+	select DRM_CLIENT_SELECTION
+	select DRM_KMS_HELPER
+	select DRM_GEM_SHMEM_HELPER
+	select REGMAP_MMIO
+	select VIDEOMODE_HELPERS
+	help
+	  Choose this option if you have a SpacemiT SoC with the Saturn
+	  display processing unit, such as the K3. The DPU scans out
+	  framebuffers through its private display MMU and feeds a
+	  DisplayPort or embedded DisplayPort controller.
+
+	  If M is selected the module will be called spacemit-drm.
diff --git a/drivers/gpu/drm/spacemit/Makefile b/drivers/gpu/drm/spacemit/Makefile
new file mode 100644
index 0000000000000..b3b148000cf7b
--- /dev/null
+++ b/drivers/gpu/drm/spacemit/Makefile
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0
+
+spacemit-drm-y := spacemit_drm.o \
+		  spacemit_crtc.o \
+		  spacemit_cmdlist.o \
+		  spacemit_planes.o \
+		  spacemit_dmmu.o \
+		  dpu/dpu_saturn.o \
+		  dpu/dpu_saturn_hee.o \
+		  dpu/saturn_fbcmem.o
+
+obj-$(CONFIG_DRM_SPACEMIT) += spacemit-drm.o
diff --git a/drivers/gpu/drm/spacemit/spacemit_drm.c b/drivers/gpu/drm/spacemit/spacemit_drm.c
new file mode 100644
index 0000000000000..12b2fe8b6fc99
--- /dev/null
+++ b/drivers/gpu/drm/spacemit/spacemit_drm.c
@@ -0,0 +1,140 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2025-2026 SpacemiT Co., Ltd.
+ *
+ */
+
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_framebuffer.h>
+#include <drm/drm_gem_framebuffer_helper.h>
+#include <drm/drm_gem_shmem_helper.h>
+#include <drm/drm_of.h>
+#include <drm/drm_fbdev_shmem.h>
+#include <linux/component.h>
+#include <linux/of_graph.h>
+
+#include "spacemit_drm.h"
+#include "spacemit_crtc.h"
+
+#define DRIVER_NAME	"spacemit"
+#define DRIVER_DESC	"SpacemiT SoC DRM driver"
+#define DRIVER_MAJOR	1
+#define DRIVER_MINOR	0
+
+static void spacemit_drm_atomic_commit_tail(struct drm_atomic_commit *old_state)
+{
+	struct drm_device *dev = old_state->dev;
+
+	drm_atomic_helper_commit_modeset_disables(dev, old_state);
+
+	drm_atomic_helper_commit_modeset_enables(dev, old_state);
+
+	drm_atomic_helper_commit_planes(dev, old_state,
+					DRM_PLANE_COMMIT_ACTIVE_ONLY);
+
+	/*
+	 * Flip first, hw_done second: the cmdlist engine reads the old
+	 * state's DMA buffers until the frame boundary, and hw_done both
+	 * releases the next commit to start programming and lets the old
+	 * state (with those buffers) be torn down.
+	 */
+	drm_atomic_helper_wait_for_flip_done(dev, old_state);
+
+	drm_atomic_helper_commit_hw_done(old_state);
+
+	drm_atomic_helper_cleanup_planes(dev, old_state);
+}
+
+static const struct drm_mode_config_helper_funcs spacemit_drm_mode_config_helper = {
+	.atomic_commit_tail = spacemit_drm_atomic_commit_tail,
+};
+
+static const struct drm_mode_config_funcs spacemit_drm_mode_config_funcs = {
+	.fb_create = drm_gem_fb_create,
+	.atomic_check = drm_atomic_helper_check,
+	.atomic_commit = drm_atomic_helper_commit,
+};
+
+int spacemit_drm_mode_config_init(struct drm_device *drm)
+{
+	int ret;
+
+	ret = drmm_mode_config_init(drm);
+	if (ret)
+		return ret;
+
+	drm->mode_config.min_width = 1;
+	drm->mode_config.min_height = 1;
+	/* K3 user manual: each DPU scans out at most 3840x2160@60 */
+	drm->mode_config.max_width = 3840;
+	drm->mode_config.max_height = 2160;
+
+	drm->mode_config.funcs = &spacemit_drm_mode_config_funcs;
+	drm->mode_config.helper_private = &spacemit_drm_mode_config_helper;
+
+	return 0;
+}
+
+DEFINE_DRM_GEM_FOPS(spacemit_drm_fops);
+
+struct drm_driver spacemit_drm_drv = {
+	.driver_features = DRIVER_GEM | DRIVER_MODESET | DRIVER_ATOMIC,
+	.fops = &spacemit_drm_fops,
+
+	DRM_GEM_SHMEM_DRIVER_OPS,
+	DRM_FBDEV_SHMEM_DRIVER_OPS,
+
+	.name		= DRIVER_NAME,
+	.desc		= DRIVER_DESC,
+	.major		= DRIVER_MAJOR,
+	.minor		= DRIVER_MINOR,
+};
+
+static int compare_of(struct device *dev, void *data)
+{
+	return dev->of_node == data;
+}
+
+int spacemit_drm_of_component_probe(struct device *dev)
+{
+	struct device_node *ports, *port, *ep;
+	struct device_node *remote;
+	struct component_match *match = NULL;
+
+	if (!dev->of_node)
+		return -EINVAL;
+
+	/* The DPU is the drm root: its OF graph names the DP/eDP components. */
+	ports = of_get_child_by_name(dev->of_node, "ports");
+	if (!ports) {
+		dev_err(dev, "missing 'ports' child node\n");
+		return -EINVAL;
+	}
+
+	for_each_child_of_node(ports, port) {
+		if (!of_node_name_eq(port, "port"))
+			continue;
+		for_each_child_of_node(port, ep) {
+			if (!of_node_name_eq(ep, "endpoint"))
+				continue;
+			remote = of_graph_get_remote_port_parent(ep);
+			if (!remote)
+				continue;
+			if (of_device_is_available(remote))
+				drm_of_component_match_add(dev, &match,
+							   compare_of, remote);
+			of_node_put(remote);
+		}
+	}
+	of_node_put(ports);
+
+	if (!match) {
+		dev_err(dev, "no downstream component available\n");
+		return -ENODEV;
+	}
+	if (IS_ERR(match))
+		return PTR_ERR(match);
+
+	return component_master_add_with_match(dev, &spacemit_drm_master_ops,
+					       match);
+}

-- 
2.43.0