Re: [PATCH v2 3/3] drm/nuvoton: add MA35D1 display controller driver

[Krzysztof Kozlowski <krzk@kernel.org>]

On Thu, Jan 29, 2026 at 12:05:32PM +0800, Joey Lu wrote:
> Add DRM driver support for the Display Control Unit (DCU)
> found in Nuvoton MA35D1 SoCs.
> 
> Signed-off-by: Joey Lu <a0987203069@gmail.com>
> ---
>  drivers/gpu/drm/Kconfig                  |   1 +
>  drivers/gpu/drm/Makefile                 |   1 +
>  drivers/gpu/drm/nuvoton/Kconfig          |  21 +
>  drivers/gpu/drm/nuvoton/Makefile         |   7 +
>  drivers/gpu/drm/nuvoton/ma35_crtc.c      | 372 ++++++++++++++
>  drivers/gpu/drm/nuvoton/ma35_crtc.h      |  67 +++
>  drivers/gpu/drm/nuvoton/ma35_drm.c       | 371 ++++++++++++++
>  drivers/gpu/drm/nuvoton/ma35_drm.h       |  48 ++
>  drivers/gpu/drm/nuvoton/ma35_interface.c | 193 ++++++++
>  drivers/gpu/drm/nuvoton/ma35_interface.h |  30 ++
>  drivers/gpu/drm/nuvoton/ma35_plane.c     | 603 +++++++++++++++++++++++
>  drivers/gpu/drm/nuvoton/ma35_plane.h     | 115 +++++
>  drivers/gpu/drm/nuvoton/ma35_regs.h      |  88 ++++

No maintainers? Why would we want to take unmaintained code?

> +static void ma35_mode_fini(struct ma35_drm *priv)
> +{
> +	struct drm_device *drm_dev = &priv->drm_dev;
> +
> +	drm_kms_helper_poll_fini(drm_dev);
> +}
> +
> +static int ma35_clocks_prepare(struct ma35_drm *priv)
> +{
> +	struct drm_device *drm_dev = &priv->drm_dev;
> +	struct device *dev = drm_dev->dev;
> +	int ret;
> +
> +	priv->dcuclk = devm_clk_get(dev, "dcu_gate");
> +	if (IS_ERR(priv->dcuclk)) {
> +		dev_err(dev, "Failed to get display core clock\n");

Don't spam logs on defers. Syntax is in entire probe path: return
dev_err_probe

> +		return PTR_ERR(priv->dcuclk);
> +	}
> +
> +	ret = clk_prepare_enable(priv->dcuclk);

Why this cannot be devm_clk_get_enabled?

> +	if (ret) {
> +		dev_err(dev, "Failed to enable display core clock\n");
> +		return ret;
> +	}
> +
> +	priv->dcupclk = devm_clk_get(dev, "dcup_div");
> +	if (IS_ERR(priv->dcupclk)) {
> +		dev_err(dev, "Failed to get display pixel clock\n");
> +		return PTR_ERR(priv->dcupclk);
> +	}
> +
> +	ret = clk_prepare_enable(priv->dcupclk);
> +	if (ret) {
> +		dev_err(dev, "Failed to enable display pixel clock\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int ma35_clocks_unprepare(struct ma35_drm *priv)
> +{
> +	struct clk **clocks[] = {
> +		&priv->dcuclk,
> +		&priv->dcupclk,
> +	};
> +	unsigned int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(clocks); i++) {
> +		if (!*clocks[i])
> +			continue;
> +
> +		clk_disable_unprepare(*clocks[i]);
> +		*clocks[i] = NULL;

Huh, pretty complicated and pointless code. This should be devm and bulk
API...

> +	}
> +
> +	return 0;
> +}
> +
> +static int ma35_drm_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct ma35_drm *priv;
> +	struct drm_device *drm_dev;
> +	void __iomem *base;
> +	struct regmap *regmap = NULL;
> +	int irq;
> +	int ret;
> +
> +	ret = of_reserved_mem_device_init(dev);
> +	if (ret && ret != -ENODEV) {
> +		dev_err(dev, "Failed to get optional reserved memory: %d\n", ret);
> +		return ret;
> +	}
> +
> +	base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(base)) {
> +		dev_err(dev, "Failed to map I/O base\n");

Why aren't you using dev_err_probe?

> +		ret = PTR_ERR(base);
> +		goto error_reserved_mem;
> +	}
> +	regmap = devm_regmap_init_mmio(dev, base, &ma35_drm_regmap_config);
> +	if (IS_ERR(regmap)) {
> +		dev_err(dev, "Failed to create regmap for I/O\n");
> +		ret = PTR_ERR(regmap);
> +		goto error_reserved_mem;
> +	}
> +
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0) {
> +		ret = -ENODEV;
> +		goto error_reserved_mem;
> +	}
> +
> +	priv = devm_drm_dev_alloc(dev, &ma35_drm_driver,
> +				     struct ma35_drm, drm_dev);
> +	if (IS_ERR(priv)) {
> +		ret = PTR_ERR(priv);
> +		goto error_reserved_mem;
> +	}
> +
> +	platform_set_drvdata(pdev, priv);
> +	drm_dev = &priv->drm_dev;
> +	priv->regmap = regmap;
> +	INIT_LIST_HEAD(&priv->layers_list);
> +
> +	ret = ma35_clocks_prepare(priv);
> +	if (ret) {
> +		drm_err(drm_dev, "Failed to prepare clocks\n");

Why do you print error twice? Once in the function, second time here?

> +		goto error_reserved_mem;
> +	}
> +
> +	ret = devm_request_irq(dev, irq, ma35_drm_irq_handler, 0,
> +			       dev_name(dev), priv);
> +	if (ret) {
> +		drm_err(drm_dev, "Failed to request IRQ\n");
> +		goto error_clocks;
> +	}
> +
> +	/* modeset */
> +	ret = ma35_mode_init(priv);
> +	if (ret) {
> +		drm_err(drm_dev, "Failed to initialize KMS\n");
> +		goto error_clocks;
> +	}
> +
> +	/* plane */
> +	ret = ma35_plane_init(priv);
> +	if (ret) {
> +		drm_err(drm_dev, "Failed to initialize layers\n");
> +		goto error_clocks;
> +	}
> +
> +	/* crtc */
> +	ret = ma35_crtc_init(priv);
> +	if (ret) {
> +		drm_err(drm_dev, "Failed to initialize CRTC\n");
> +		goto error_clocks;
> +	}
> +
> +	/* interface */
> +	ret = ma35_interface_init(priv);
> +	if (ret) {
> +		if (ret != -EPROBE_DEFER)
> +			drm_err(drm_dev, "Failed to initialize interface\n");
> +
> +		goto error_clocks;
> +	}
> +
> +	drm_mode_config_reset(drm_dev);
> +
> +	ret = drm_dev_register(drm_dev, 0);
> +	if (ret) {
> +		drm_err(drm_dev, "Failed to register DRM device\n");
> +		goto error_mode;
> +	}
> +
> +	drm_client_setup(drm_dev, NULL);

Best regards,
Krzysztof