Re: [PATCH 3/3] drm: renesas: rz-du: Add support for RZ/G3L LVDS encoder

[Dmitry Baryshkov]

On Fri, Apr 17, 2026 at 06:52:30PM +0100, Biju wrote:
> From: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> 
> Add support for the RZ/G3L LVDS encoder driver. It operates in single-link
> mode with 4 lanes (Data) + 1 lane (Clock) and supports pixel clock rates
> from 25 to 87 MHz. The LVDS module cannot be used at the same time as
> MIPI-DSI. However, LVDS and the DSI interface share a peripheral clock and
> the MIPI_DSI_PRESET_N reset signal. Also, the MIPI_DSI_CMN_RSTB and
> MIPI_DSI_ARESET_N reset signals must be asserted before using the LVDS
> module.
> 
> Signed-off-by: Tommaso Merciai <tommaso.merciai.xr@xxxxxxxxxxxxxx>
> Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/renesas/rz-du/Kconfig         |  13 +
>  drivers/gpu/drm/renesas/rz-du/Makefile        |   1 +
>  drivers/gpu/drm/renesas/rz-du/rzg3l_lvds.c    | 333 ++++++++++++++++++
>  drivers/gpu/drm/renesas/rz-du/rzg3l_lvds.h    |  22 ++
>  .../gpu/drm/renesas/rz-du/rzg3l_lvds_regs.h   |  26 ++
>  5 files changed, 395 insertions(+)
>  create mode 100644 drivers/gpu/drm/renesas/rz-du/rzg3l_lvds.c
>  create mode 100644 drivers/gpu/drm/renesas/rz-du/rzg3l_lvds.h
>  create mode 100644 drivers/gpu/drm/renesas/rz-du/rzg3l_lvds_regs.h
> 
> diff --git a/drivers/gpu/drm/renesas/rz-du/Kconfig b/drivers/gpu/drm/renesas/rz-du/Kconfig
> index 7f2ef7137ae5..cbfc7b6bccb8 100644
> --- a/drivers/gpu/drm/renesas/rz-du/Kconfig
> +++ b/drivers/gpu/drm/renesas/rz-du/Kconfig
> @@ -26,3 +26,16 @@ config DRM_RZG2L_MIPI_DSI
>  	def_tristate DRM_RZG2L_DU
>  	depends on DRM_RZG2L_USE_MIPI_DSI
>  	select DRM_MIPI_DSI
> +
> +config DRM_RZG3L_USE_LVDS
> +	bool "RZ/G3L DU LVDS Encoder Support"
> +	depends on DRM_BRIDGE && OF
> +	default DRM_RZG2L_DU
> +	help
> +	  Enable support for the RZ/G3L Display Unit embedded LVDS encoders.
> +
> +config DRM_RZG3L_LVDS
> +	def_tristate DRM_RZG2L_DU
> +	depends on DRM_RZG3L_USE_LVDS
> +	select DRM_KMS_HELPER
> +	select DRM_PANEL
> diff --git a/drivers/gpu/drm/renesas/rz-du/Makefile b/drivers/gpu/drm/renesas/rz-du/Makefile
> index 2987900ea6b6..46decb7ac4f1 100644
> --- a/drivers/gpu/drm/renesas/rz-du/Makefile
> +++ b/drivers/gpu/drm/renesas/rz-du/Makefile
> @@ -8,3 +8,4 @@ rzg2l-du-drm-$(CONFIG_VIDEO_RENESAS_VSP1)	+= rzg2l_du_vsp.o
>  obj-$(CONFIG_DRM_RZG2L_DU)		+= rzg2l-du-drm.o
>  
>  obj-$(CONFIG_DRM_RZG2L_MIPI_DSI)	+= rzg2l_mipi_dsi.o
> +obj-$(CONFIG_DRM_RZG3L_LVDS)		+= rzg3l_lvds.o
> diff --git a/drivers/gpu/drm/renesas/rz-du/rzg3l_lvds.c b/drivers/gpu/drm/renesas/rz-du/rzg3l_lvds.c
> new file mode 100644
> index 000000000000..bedeedbdfada
> --- /dev/null
> +++ b/drivers/gpu/drm/renesas/rz-du/rzg3l_lvds.c
> @@ -0,0 +1,333 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * RZ/G3L LVDS Encoder Driver
> + *
> + * Copyright (C) 2026 Renesas Electronics Corporation
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/io.h>
> +#include <linux/media-bus-format.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/of_graph.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/regmap.h>
> +#include <linux/reset.h>
> +
> +#include <drm/drm_atomic.h>
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_bridge.h>
> +#include <drm/drm_of.h>
> +#include <drm/drm_panel.h>
> +#include <drm/drm_probe_helper.h>
> +
> +#include "rzg3l_lvds.h"
> +#include "rzg3l_lvds_regs.h"
> +
> +enum rzg3l_lvds_mode {
> +	RZG3L_LVDS_MODE_JEIDA = 0,
> +	RZG3L_LVDS_MODE_JEIDA_MIRROR = 1,
> +	RZG3L_LVDS_MODE_MODE2 = 2,
> +	RZG3L_LVDS_MODE_MODE2_MIRROR = 3,
> +	RZG3L_LVDS_MODE_VESA = 4,
> +	RZG3L_LVDS_MODE_VESA_MIRROR = 5,
> +	RZG3L_LVDS_MODE_MODE6 = 6,
> +	RZG3L_LVDS_MODE_MODE6_MIRROR = 7,
> +};
> +
> +struct rzg3l_lvds {
> +	struct device *dev;
> +	struct reset_control *prstc;
> +	struct reset_control *lvd_rstc;
> +	struct regmap *regmap;
> +
> +	struct drm_bridge bridge;
> +	struct drm_bridge *next_bridge;

Please use next_bridge from the drm_bridge struct.

> +};
> +
> +#define bridge_to_rzg3l_lvds(b) \
> +	container_of(b, struct rzg3l_lvds, bridge)
> +
> +/* -----------------------------------------------------------------------------
> + * Bridge
> + */
> +static void rzg3l_lvds_atomic_enable(struct drm_bridge *bridge,
> +				     struct drm_atomic_state *state)
> +{
> +	struct rzg3l_lvds *lvds = bridge_to_rzg3l_lvds(bridge);
> +	const struct drm_bridge_state *bridge_state;
> +	int ret;
> +	u32 fmt;
> +
> +	/* Get the LVDS format from the bridge state. */
> +	bridge_state = drm_atomic_get_new_bridge_state(state, bridge);
> +	if (!bridge_state) {
> +		dev_err(lvds->dev, "failed to get bridge state\n");
> +		return;
> +	}
> +
> +	switch (bridge_state->output_bus_cfg.format) {
> +	case MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA:
> +		fmt = RZG3L_LVDS_MODE_JEIDA;
> +		break;
> +	case MEDIA_BUS_FMT_RGB888_1X7X4_SPWG:
> +		fmt = RZG3L_LVDS_MODE_VESA;
> +		break;
> +	default:
> +		fmt = RZG3L_LVDS_MODE_VESA;
> +		dev_warn(lvds->dev, "Unsupported bus fmt 0x%04x\n",
> +			 bridge_state->output_bus_cfg.format);
> +		break;
> +	}
> +
> +	ret = pm_runtime_resume_and_get(lvds->dev);

If this  fails for any reason, the atomic_disable() would still be
called and it will decrement the counter, potentially undeflowing it.
Consider switching to pm_runtime_get_sync(), which suits better here.


> +	if (ret < 0) {
> +		dev_err(lvds->dev, "pm_runtime_resume_and_get error\n");
> +		return;
> +	}
> +
> +	regmap_update_bits(lvds->regmap, LVDS_0_PHY_OFFSET,
> +			   LVDS_0_PHY_CH_EN_BGR, LVDS_0_PHY_CH_EN_BGR);
> +	usleep_range(20, 25);
> +
> +	regmap_update_bits(lvds->regmap, LVDS_0_PHY_OFFSET,
> +			   LVDS_0_PHY_CH_EN_LDO, LVDS_0_PHY_CH_EN_LDO);
> +	usleep_range(10, 15);
> +
> +	regmap_write(lvds->regmap, LVDS_CMN, LVDS_CMN_RST_PHY0_SEL);
> +	regmap_update_bits(lvds->regmap, LVDS_0_CTL_OFFSET,
> +			   LVDS_0_CTL_FMT_SEL_MSK,
> +			   FIELD_PREP(LVDS_0_CTL_FMT_SEL_MSK, fmt));
> +	regmap_update_bits(lvds->regmap, LVDS_0_PHY_OFFSET,
> +			   LVDS_0_PHY_CH_IO_EN_MSK, LVDS_0_PHY_CH_IO_EN);
> +	regmap_write(lvds->regmap, LVDS_CMN,
> +		     LVDS_CMN_RST_PHY0_SEL | LVDS_CMN_PHY_RESET);
> +	usleep_range(100, 150);
> +}
> +
> +static void rzg3l_lvds_atomic_disable(struct drm_bridge *bridge,
> +				      struct drm_atomic_state *state)
> +{
> +	struct rzg3l_lvds *lvds = bridge_to_rzg3l_lvds(bridge);
> +
> +	regmap_update_bits(lvds->regmap, LVDS_CMN, LVDS_CMN_PHY_RESET, 0);
> +	regmap_update_bits(lvds->regmap, LVDS_0_PHY_OFFSET,
> +			   LVDS_0_PHY_CH_IO_EN_MSK, 0);
> +	regmap_update_bits(lvds->regmap, LVDS_0_PHY_OFFSET,
> +			   LVDS_0_PHY_CH_EN_LDO, 0);
> +	regmap_update_bits(lvds->regmap, LVDS_0_PHY_OFFSET,
> +			   LVDS_0_PHY_CH_EN_BGR, 0);
> +
> +	pm_runtime_put(lvds->dev);
> +}
> +
> +static int rzg3l_lvds_attach(struct drm_bridge *bridge,
> +			     struct drm_encoder *encoder,
> +			     enum drm_bridge_attach_flags flags)
> +{
> +	struct rzg3l_lvds *lvds = bridge_to_rzg3l_lvds(bridge);
> +
> +	if (!lvds->next_bridge)
> +		return 0;
> +
> +	return drm_bridge_attach(encoder, lvds->next_bridge, bridge, flags);
> +}
> +
> +static enum drm_mode_status
> +rzg3l_lvds_bridge_mode_valid(struct drm_bridge *bridge,
> +			     const struct drm_display_info *info,
> +			     const struct drm_display_mode *mode)
> +{
> +	if (mode->clock > 87000)
> +		return MODE_CLOCK_HIGH;
> +
> +	if (mode->clock < 25000)
> +		return MODE_CLOCK_LOW;
> +
> +	return MODE_OK;
> +}
> +
> +bool rzg3l_lvds_is_connected(struct drm_bridge *bridge)
> +{
> +	struct rzg3l_lvds *lvds = bridge_to_rzg3l_lvds(bridge);
> +
> +	return !!lvds->next_bridge;
> +}
> +EXPORT_SYMBOL_GPL(rzg3l_lvds_is_connected);

How is this going to be used? I don't see the user in the patch. Please
drop the unused API.

> +
> +static const struct drm_bridge_funcs rzg3l_lvds_bridge_ops = {
> +	.attach = rzg3l_lvds_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 = rzg3l_lvds_atomic_enable,
> +	.atomic_disable = rzg3l_lvds_atomic_disable,
> +	.mode_valid = rzg3l_lvds_bridge_mode_valid,
> +};
> +
> +/* -----------------------------------------------------------------------------
> + * Power Management
> + */
> +
> +static int rzg3l_lvds_pm_runtime_suspend(struct device *dev)
> +{
> +	struct rzg3l_lvds *lvds = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = reset_control_assert(lvds->lvd_rstc);
> +	if (ret)
> +		return ret;
> +
> +	ret = reset_control_assert(lvds->prstc);
> +	if (ret)
> +		goto err_deassert_lvd_rstc;
> +
> +	return 0;
> +
> +err_deassert_lvd_rstc:
> +	reset_control_deassert(lvds->lvd_rstc);
> +	return ret;
> +}
> +
> +static int rzg3l_lvds_pm_runtime_resume(struct device *dev)
> +{
> +	struct rzg3l_lvds *lvds = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = reset_control_deassert(lvds->prstc);
> +	if (ret)
> +		return ret;
> +
> +	return reset_control_deassert(lvds->lvd_rstc);
> +	if (ret)
> +		goto err_assert_prstc;
> +
> +	return 0;
> +
> +err_assert_prstc:
> +	reset_control_assert(lvds->prstc);
> +	return ret;
> +}
> +
> +static const struct dev_pm_ops rzg3l_lvds_pm_ops = {
> +	RUNTIME_PM_OPS(rzg3l_lvds_pm_runtime_suspend,
> +		       rzg3l_lvds_pm_runtime_resume, NULL)
> +	SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
> +};

DEFINE_RUNTIME_DEV_PM_OPS()

> +
> +/* -----------------------------------------------------------------------------
> + * Probe & Remove
> + */
> +
> +static int rzg3l_lvds_parse_dt(struct rzg3l_lvds *lvds)
> +{
> +	struct device *dev = lvds->dev;
> +	struct drm_panel *panel;
> +	int ret;
> +
> +	ret = drm_of_find_panel_or_bridge(dev->of_node, 1, 0,
> +					  &panel, &lvds->next_bridge);
> +	if (ret)
> +		return ret;
> +
> +	if (panel) {
> +		lvds->next_bridge = devm_drm_panel_bridge_add(dev, panel);
> +		if (IS_ERR_OR_NULL(lvds->next_bridge))
> +			return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +static int rzg3l_lvds_probe(struct platform_device *pdev)
> +{
> +	struct reset_control *rstc, *arstc;
> +	struct device *dev = &pdev->dev;
> +	struct rzg3l_lvds *lvds;
> +	int ret;
> +
> +	lvds = devm_drm_bridge_alloc(dev, struct rzg3l_lvds, bridge,
> +				     &rzg3l_lvds_bridge_ops);
> +	if (IS_ERR(lvds))
> +		return PTR_ERR(lvds);
> +
> +	lvds->dev = dev;
> +	lvds->bridge.of_node = pdev->dev.of_node;
> +
> +	lvds->regmap = syscon_node_to_regmap(dev->of_node->parent);
> +	if (IS_ERR(lvds->regmap))
> +		return PTR_ERR(lvds->regmap);
> +
> +	rstc = devm_reset_control_get_optional_exclusive(dev, "rst");
> +	if (IS_ERR(rstc))
> +		return dev_err_probe(dev, PTR_ERR(rstc), "failed to get rst\n");
> +
> +	arstc = devm_reset_control_get_optional_exclusive(dev, "arst");
> +	if (IS_ERR(arstc))
> +		return dev_err_probe(dev, PTR_ERR(arstc),
> +				     "failed to get arst\n");
> +
> +	lvds->prstc = devm_reset_control_get_shared(dev, "prst");
> +	if (IS_ERR(lvds->prstc))
> +		return dev_err_probe(dev, PTR_ERR(lvds->prstc),
> +				     "failed to get prst\n");
> +
> +	lvds->lvd_rstc = devm_reset_control_get_shared(dev, "lvdrst");
> +	if (IS_ERR(lvds->lvd_rstc))
> +		return dev_err_probe(dev, PTR_ERR(lvds->lvd_rstc),
> +				     "failed to get core reset\n");
> +
> +	platform_set_drvdata(pdev, lvds);
> +
> +	ret = devm_pm_runtime_enable(dev);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to enable Runtime PM\n");
> +
> +	ret = rzg3l_lvds_parse_dt(lvds);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = reset_control_assert(rstc);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = reset_control_assert(arstc);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = devm_drm_bridge_add(dev, &lvds->bridge);
> +	if (ret)
> +		return dev_err_probe(dev, ret,
> +				     "Failed to register drm bridge\n");
> +
> +	return ret;
> +}
> +
> +static const struct of_device_id rzg3l_lvds_of_table[] = {
> +	{ .compatible = "renesas,r9a08g046-lvds" },
> +	{ /* sentinel */ }
> +};
> +
> +MODULE_DEVICE_TABLE(of, rzg3l_lvds_of_table);
> +
> +static struct platform_driver rzg3l_lvds_platform_driver = {
> +	.probe		= rzg3l_lvds_probe,
> +	.driver		= {
> +		.name	= "rzg3l-lvds",
> +		.pm	= pm_ptr(&rzg3l_lvds_pm_ops),
> +		.of_match_table = rzg3l_lvds_of_table,
> +	},
> +};
> +
> +module_platform_driver(rzg3l_lvds_platform_driver);
> +
> +MODULE_AUTHOR("Biju Das <biju.das.jz@xxxxxxxxxxxxxx>");
> +MODULE_AUTHOR("Tommaso Merciai <tommaso.merciai.xr@xxxxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("Renesas RZ/G3L LVDS Encoder Driver");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/gpu/drm/renesas/rz-du/rzg3l_lvds.h b/drivers/gpu/drm/renesas/rz-du/rzg3l_lvds.h
> new file mode 100644
> index 000000000000..2ea3cf4e1cae
> --- /dev/null
> +++ b/drivers/gpu/drm/renesas/rz-du/rzg3l_lvds.h
> @@ -0,0 +1,22 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * RZ/G3L LVDS Encoder
> + *
> + * Copyright (C) 2026 Renesas Electronics Corporation
> + *
> + */
> +
> +#ifndef __RZG3L_LVDS_H__
> +#define __RZG3L_LVDS_H__
> +
> +struct drm_bridge;
> +
> +#if IS_ENABLED(CONFIG_DRM_RZG3L_LVDS)
> +bool rzg3l_lvds_is_connected(struct drm_bridge *bridge);
> +#else
> +static inline bool rzg3l_lvds_is_connected(struct drm_bridge *bridge)
> +{
> +	return false;
> +}
> +#endif /* CONFIG_DRM_RZG3L_LVDS */
> +#endif /* __RZG3L_LVDS_H__ */
> diff --git a/drivers/gpu/drm/renesas/rz-du/rzg3l_lvds_regs.h b/drivers/gpu/drm/renesas/rz-du/rzg3l_lvds_regs.h
> new file mode 100644
> index 000000000000..281b7648f168
> --- /dev/null
> +++ b/drivers/gpu/drm/renesas/rz-du/rzg3l_lvds_regs.h
> @@ -0,0 +1,26 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * RZ/G3L LVDS Interface Registers Definitions
> + *
> + * Copyright (C) 2026 Renesas Electronics Corporation
> + *
> + */
> +
> +#ifndef __RZG3L_LVDS_REGS_H__
> +#define __RZG3L_LVDS_REGS_H__
> +
> +#define LVDS_CMN			0x00
> +#define LVDS_CMN_RST_PHY0_SEL		(1 << 24)
> +#define LVDS_CMN_RST_PHY0_SEL_CH0	(1 << 24)
> +#define LVDS_CMN_PHY_RESET		(1 << 0)
> +
> +#define LVDS_0_PHY_OFFSET		0x10
> +#define LVDS_0_PHY_CH_IO_EN_MSK		(0x1f)
> +#define LVDS_0_PHY_CH_IO_EN		(LVDS_0_PHY_CH_IO_EN_MSK << 0)
> +#define LVDS_0_PHY_CH_EN_BGR		BIT(8)
> +#define LVDS_0_PHY_CH_EN_LDO		BIT(9)
> +
> +#define LVDS_0_CTL_OFFSET		0x14
> +#define LVDS_0_CTL_FMT_SEL_MSK		GENMASK(23, 20)
> +
> +#endif /* __RZG3L_LVDS_REGS_H__ */
> -- 
> 2.43.0
> 

-- 
With best wishes
Dmitry