[PATCH v2 11/17] drm/spacemit: add Saturn DPU DRM device driver
Icenowy Zheng
uwu at icenowy.me
Thu Sep 3 05:07:32 PDT 2026
在 2026-08-09日的 21:14 +0800，Cody Kang via B4 Relay写道：
> From: Cody Kang <codykang.hk at 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 at 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 at 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 at 60
> */
> + drm->mode_config.max_width = 3840;
> + drm->mode_config.max_height = 2160;
This is for the biggest possible framebuffer instead of the possible
scanout pixel count.
The width here should be based on the maximum allowed pitch of the
display controller instead of the single-GPU maximum size, otherwise it
won't be able to drive two 3840x2160 screens in a side-by-side
configuration because this will create a 7680x2160 framebuffer.
Thanks,
Icenowy
> +
> + 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);
> +}
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