Re: [PATCH v3 3/7] drm/rcar-du: dsc: Add rudimentary Renesas R-Car V4H DSC driver

[Laurent Pinchart]

Hi Tomi, Marek,

Thank you for the patch.

On Fri, May 15, 2026 at 12:09:28PM +0300, Tomi Valkeinen wrote:
> From: Marek Vasut <marek.vasut+renesas@xxxxxxxxxxx>
> 
> The Renesas DSC Display Stream Compression is a bridge embedded in the
> Renesas R-Car V4H SoC. The bridge performs VESA DSC encoding of up to
> 8k or 400 Mpixel/s . Add rudimentary driver, which currently acts as a

s/s \./s./

> pass-through bridge and allows DSI1 to be operational on R-Car V4H.
> 
> Signed-off-by: Marek Vasut <marek.vasut+renesas@xxxxxxxxxxx>
> [tomi.valkeinen: use bridge->next_bridge, minor changes]
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@xxxxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/renesas/rcar-du/Kconfig    |  12 +++
>  drivers/gpu/drm/renesas/rcar-du/Makefile   |   1 +
>  drivers/gpu/drm/renesas/rcar-du/rcar_dsc.c | 160 +++++++++++++++++++++++++++++
>  3 files changed, 173 insertions(+)
> 
> diff --git a/drivers/gpu/drm/renesas/rcar-du/Kconfig b/drivers/gpu/drm/renesas/rcar-du/Kconfig
> index 840305fdeb49..c58dba949d85 100644
> --- a/drivers/gpu/drm/renesas/rcar-du/Kconfig
> +++ b/drivers/gpu/drm/renesas/rcar-du/Kconfig
> @@ -33,6 +33,18 @@ config DRM_RCAR_DW_HDMI
>  	help
>  	  Enable support for R-Car Gen3 or RZ/G2 internal HDMI encoder.
>  
> +config DRM_RCAR_USE_DSC
> +	bool "R-Car DU DSC Encoder Support"
> +	depends on DRM_BRIDGE && OF
> +	depends on DRM_RCAR_DU || COMPILE_TEST
> +	default DRM_RCAR_DU
> +	help
> +	  Enable support for the R-Car Display Unit embedded DSC encoder.
> +
> +config DRM_RCAR_DSC
> +	def_tristate DRM_RCAR_DU
> +	depends on DRM_RCAR_USE_DSC
> +

Nitpicking, I'd move this above CMM, for preserve alphabetical ordering
of the blocks.

>  config DRM_RCAR_USE_LVDS
>  	bool "R-Car DU LVDS Encoder Support"
>  	depends on DRM_BRIDGE && OF
> diff --git a/drivers/gpu/drm/renesas/rcar-du/Makefile b/drivers/gpu/drm/renesas/rcar-du/Makefile
> index 6f132325c8b7..cc27b2265d94 100644
> --- a/drivers/gpu/drm/renesas/rcar-du/Makefile
> +++ b/drivers/gpu/drm/renesas/rcar-du/Makefile
> @@ -12,5 +12,6 @@ rcar-du-drm-$(CONFIG_DRM_RCAR_WRITEBACK) += rcar_du_writeback.o
>  obj-$(CONFIG_DRM_RCAR_CMM)		+= rcar_cmm.o
>  obj-$(CONFIG_DRM_RCAR_DU)		+= rcar-du-drm.o
>  obj-$(CONFIG_DRM_RCAR_DW_HDMI)		+= rcar_dw_hdmi.o
> +obj-$(CONFIG_DRM_RCAR_DSC)		+= rcar_dsc.o

Here too.

>  obj-$(CONFIG_DRM_RCAR_LVDS)		+= rcar_lvds.o
>  obj-$(CONFIG_DRM_RCAR_MIPI_DSI)		+= rcar_mipi_dsi.o
> diff --git a/drivers/gpu/drm/renesas/rcar-du/rcar_dsc.c b/drivers/gpu/drm/renesas/rcar-du/rcar_dsc.c
> new file mode 100644
> index 000000000000..5d3d083e3ce6
> --- /dev/null
> +++ b/drivers/gpu/drm/renesas/rcar-du/rcar_dsc.c
> @@ -0,0 +1,160 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * R-Car DSC Encoder
> + *
> + * Copyright (C) 2025 Marek Vasut <marek.vasut+renesas@xxxxxxxxxxx>
> + * Copyright (C) 2025 Renesas Electronics Corporation
> + */
> +

#include <linux/container_of.h>

> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_graph.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
> +
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_bridge.h>
> +#include <drm/drm_of.h>

I think you can drop drm_of.h.

> +
> +struct rcar_dsc {
> +	struct drm_bridge bridge;
> +
> +	struct device *dev;
> +	void __iomem *mmio;
> +};
> +
> +static inline struct rcar_dsc *bridge_to_rcar_dsc(struct drm_bridge *bridge)
> +{
> +	return container_of(bridge, struct rcar_dsc, bridge);
> +}
> +
> +/* -----------------------------------------------------------------------------
> + * Bridge
> + */
> +
> +static int rcar_dsc_attach(struct drm_bridge *bridge,
> +			   struct drm_encoder *encoder,
> +			   enum drm_bridge_attach_flags flags)
> +{
> +	struct rcar_dsc *dsc = bridge_to_rcar_dsc(bridge);
> +
> +	if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
> +		return -EINVAL;
> +
> +	return drm_bridge_attach(encoder, dsc->bridge.next_bridge, bridge,
> +				 DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> +}
> +
> +static void rcar_dsc_atomic_enable(struct drm_bridge *bridge,
> +				   struct drm_atomic_state *state)

Small conflict when rebasing on top of drm-misc.

> +{
> +	struct rcar_dsc *dsc = bridge_to_rcar_dsc(bridge);
> +
> +	WARN_ON(pm_runtime_resume_and_get(dsc->dev));
> +}
> +
> +static void rcar_dsc_atomic_disable(struct drm_bridge *bridge,
> +				    struct drm_atomic_state *state)
> +{
> +	struct rcar_dsc *dsc = bridge_to_rcar_dsc(bridge);
> +
> +	pm_runtime_put(dsc->dev);
> +}
> +
> +static enum drm_mode_status
> +rcar_dsc_bridge_mode_valid(struct drm_bridge *bridge,
> +			   const struct drm_display_info *info,
> +			   const struct drm_display_mode *mode)
> +{
> +	if (mode->hdisplay < 320 || mode->hdisplay > 8190)
> +		return MODE_BAD_HVALUE;
> +
> +	if (mode->vdisplay < 160 || mode->vdisplay > 8190)
> +		return MODE_BAD_VVALUE;
> +
> +	if (mode->clock > 400000) /* Really 400 Mpixel/s */
> +		return MODE_CLOCK_HIGH;
> +
> +	return MODE_OK;
> +}
> +
> +static const struct drm_bridge_funcs rcar_dsc_bridge_ops = {
> +	.attach = rcar_dsc_attach,
> +	.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_enable = rcar_dsc_atomic_enable,
> +	.atomic_disable = rcar_dsc_atomic_disable,
> +	.mode_valid = rcar_dsc_bridge_mode_valid,
> +};
> +
> +/* -----------------------------------------------------------------------------
> + * Probe & Remove
> + */
> +
> +static int rcar_dsc_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device_node *remote;
> +	struct rcar_dsc *dsc;
> +	int ret;
> +
> +	dsc = devm_drm_bridge_alloc(dev, struct rcar_dsc, bridge,
> +				    &rcar_dsc_bridge_ops);
> +	if (IS_ERR(dsc))
> +		return PTR_ERR(dsc);
> +
> +	platform_set_drvdata(pdev, dsc);
> +
> +	dsc->dev = &pdev->dev;
> +
> +	dsc->mmio = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(dsc->mmio))
> +		return PTR_ERR(dsc->mmio);

The driver doesn't access registers, so this can be dropped (along with
the mmio field in the rcar_dsc structure).

> +
> +	remote = of_graph_get_remote_node(dev->of_node, 1, 0);
> +	if (!remote)
> +		return -EINVAL;
> +
> +	dsc->bridge.next_bridge = of_drm_find_and_get_bridge(remote);
> +	of_node_put(remote);

You can replace this with

	dsc->bridge.next_bridge = of_drm_get_bridge_by_endpoint(dev->of_node,
								1, 0);

and drop inclusion of of_graph.h.

> +	if (!dsc->bridge.next_bridge)
> +		return -EPROBE_DEFER;
> +
> +	dsc->bridge.of_node = dev->of_node;
> +
> +	ret = devm_drm_bridge_add(dev, &dsc->bridge);
> +	if (ret)
> +		return ret;
> +
> +	pm_runtime_enable(&pdev->dev);
> +
> +	return 0;
> +}
> +
> +static void rcar_dsc_remove(struct platform_device *pdev)
> +{
> +	pm_runtime_disable(&pdev->dev);
> +}
> +
> +static const struct of_device_id rcar_dsc_of_table[] = {
> +	{ .compatible = "renesas,r8a779g0-dsc" },
> +	{}
> +};
> +
> +MODULE_DEVICE_TABLE(of, rcar_dsc_of_table);
> +
> +static struct platform_driver rcar_dsc_platform_driver = {
> +	.probe          = rcar_dsc_probe,
> +	.remove		= rcar_dsc_remove,
> +	.driver         = {
> +		.name   = "rcar-dsc",
> +		.of_match_table = rcar_dsc_of_table,
> +	},
> +};
> +
> +module_platform_driver(rcar_dsc_platform_driver);
> +
> +MODULE_DESCRIPTION("Renesas R-Car DSC Encoder Driver");
> +MODULE_LICENSE("GPL");

-- 
Regards,

Laurent Pinchart