drm: rcar-du: Add support for CMM

Add a driver for the R-Car Display Unit Color Correction Module.

In most of Gen3 SoCs, each DU output channel is provided with a CMM unit
to perform image enhancement and color correction.

Add support for CMM through a driver that supports configuration of
the 1-dimensional LUT table. More advanced CMM features will be
implemented on top of this initial one.

Reviewed-by: Laurent Pinchart <[e-mail]>
Reviewed-by: Kieran Bingham <[e-mail]>
Signed-off-by: Jacopo Mondi <[e-mail]>
Signed-off-by: Laurent Pinchart <[e-mail]>

drivers/gpu/drm/rcar-du/Kconfig

···
 	depends on DRM && OF
 	depends on ARM || ARM64
 	depends on ARCH_RENESAS || COMPILE_TEST
+	imply DRM_RCAR_CMM
 	imply DRM_RCAR_LVDS
 	select DRM_KMS_HELPER
 	select DRM_KMS_CMA_HELPER
···
 	help
 	  Choose this option if you have an R-Car chipset.
 	  If M is selected the module will be called rcar-du-drm.
+
+config DRM_RCAR_CMM
+	tristate "R-Car DU Color Management Module (CMM) Support"
+	depends on DRM && OF
+	depends on DRM_RCAR_DU
+	help
+	  Enable support for R-Car Color Management Module (CMM).
 
 config DRM_RCAR_DW_HDMI
 	tristate "R-Car DU Gen3 HDMI Encoder Support"

drivers/gpu/drm/rcar-du/Makefile

···
 rcar-du-drm-$(CONFIG_DRM_RCAR_VSP)	+= rcar_du_vsp.o
 rcar-du-drm-$(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_LVDS)		+= rcar_lvds.o

drivers/gpu/drm/rcar-du/rcar_cmm.c

···
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * rcar_cmm.c -- R-Car Display Unit Color Management Module
+ *
+ * Copyright (C) 2019 Jacopo Mondi <[e-mail]>
+ */
+
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+
+#include <drm/drm_color_mgmt.h>
+
+#include "rcar_cmm.h"
+
+#define CM2_LUT_CTRL		0x0000
+#define CM2_LUT_CTRL_LUT_EN	BIT(0)
+#define CM2_LUT_TBL_BASE	0x0600
+#define CM2_LUT_TBL(__i)	(CM2_LUT_TBL_BASE + (__i) * 4)
+
+struct rcar_cmm {
+	void __iomem *base;
+
+	/*
+	 * @lut:		1D-LUT state
+	 * @lut.enabled:	1D-LUT enabled flag
+	 */
+	struct {
+		bool enabled;
+	} lut;
+};
+
+static inline int rcar_cmm_read(struct rcar_cmm *rcmm, u32 reg)
+{
+	return ioread32(rcmm->base + reg);
+}
+
+static inline void rcar_cmm_write(struct rcar_cmm *rcmm, u32 reg, u32 data)
+{
+	iowrite32(data, rcmm->base + reg);
+}
+
+/*
+ * rcar_cmm_lut_write() - Scale the DRM LUT table entries to hardware precision
+ *			  and write to the CMM registers
+ * @rcmm: Pointer to the CMM device
+ * @drm_lut: Pointer to the DRM LUT table
+ */
+static void rcar_cmm_lut_write(struct rcar_cmm *rcmm,
+			       const struct drm_color_lut *drm_lut)
+{
+	unsigned int i;
+
+	for (i = 0; i < CM2_LUT_SIZE; ++i) {
+		u32 entry = drm_color_lut_extract(drm_lut[i].red, 8) << 16
+			  | drm_color_lut_extract(drm_lut[i].green, 8) << 8
+			  | drm_color_lut_extract(drm_lut[i].blue, 8);
+
+		rcar_cmm_write(rcmm, CM2_LUT_TBL(i), entry);
+	}
+}
+
+/*
+ * rcar_cmm_setup() - Configure the CMM unit
+ * @pdev: The platform device associated with the CMM instance
+ * @config: The CMM unit configuration
+ *
+ * Configure the CMM unit with the given configuration. Currently enabling,
+ * disabling and programming of the 1-D LUT unit is supported.
+ *
+ * As rcar_cmm_setup() accesses the CMM registers the unit should be powered
+ * and its functional clock enabled. To guarantee this, before any call to
+ * this function is made, the CMM unit has to be enabled by calling
+ * rcar_cmm_enable() first.
+ *
+ * TODO: Add support for LUT double buffer operations to avoid updating the
+ * LUT table entries while a frame is being displayed.
+ */
+int rcar_cmm_setup(struct platform_device *pdev,
+		   const struct rcar_cmm_config *config)
+{
+	struct rcar_cmm *rcmm = platform_get_drvdata(pdev);
+
+	/* Disable LUT if no table is provided. */
+	if (!config->lut.table) {
+		if (rcmm->lut.enabled) {
+			rcar_cmm_write(rcmm, CM2_LUT_CTRL, 0);
+			rcmm->lut.enabled = false;
+		}
+
+		return 0;
+	}
+
+	/* Enable LUT and program the new gamma table values. */
+	if (!rcmm->lut.enabled) {
+		rcar_cmm_write(rcmm, CM2_LUT_CTRL, CM2_LUT_CTRL_LUT_EN);
+		rcmm->lut.enabled = true;
+	}
+
+	rcar_cmm_lut_write(rcmm, config->lut.table);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(rcar_cmm_setup);
+
+/*
+ * rcar_cmm_enable() - Enable the CMM unit
+ * @pdev: The platform device associated with the CMM instance
+ *
+ * When the output of the corresponding DU channel is routed to the CMM unit,
+ * the unit shall be enabled before the DU channel is started, and remain
+ * enabled until the channel is stopped. The CMM unit shall be disabled with
+ * rcar_cmm_disable().
+ *
+ * Calls to rcar_cmm_enable() and rcar_cmm_disable() are not reference-counted.
+ * It is an error to attempt to enable an already enabled CMM unit, or to
+ * attempt to disable a disabled unit.
+ */
+int rcar_cmm_enable(struct platform_device *pdev)
+{
+	int ret;
+
+	ret = pm_runtime_get_sync(&pdev->dev);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(rcar_cmm_enable);
+
+/*
+ * rcar_cmm_disable() - Disable the CMM unit
+ * @pdev: The platform device associated with the CMM instance
+ *
+ * See rcar_cmm_enable() for usage information.
+ *
+ * Disabling the CMM unit disable all the internal processing blocks. The CMM
+ * state shall thus be restored with rcar_cmm_setup() when re-enabling the CMM
+ * unit after the next rcar_cmm_enable() call.
+ */
+void rcar_cmm_disable(struct platform_device *pdev)
+{
+	struct rcar_cmm *rcmm = platform_get_drvdata(pdev);
+
+	rcar_cmm_write(rcmm, CM2_LUT_CTRL, 0);
+	rcmm->lut.enabled = false;
+
+	pm_runtime_put(&pdev->dev);
+}
+EXPORT_SYMBOL_GPL(rcar_cmm_disable);
+
+/*
+ * rcar_cmm_init() - Initialize the CMM unit
+ * @pdev: The platform device associated with the CMM instance
+ *
+ * Return: 0 on success, -EPROBE_DEFER if the CMM is not available yet,
+ *         -ENODEV if the DRM_RCAR_CMM config option is disabled
+ */
+int rcar_cmm_init(struct platform_device *pdev)
+{
+	struct rcar_cmm *rcmm = platform_get_drvdata(pdev);
+
+	if (!rcmm)
+		return -EPROBE_DEFER;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(rcar_cmm_init);
+
+static int rcar_cmm_probe(struct platform_device *pdev)
+{
+	struct rcar_cmm *rcmm;
+
+	rcmm = devm_kzalloc(&pdev->dev, sizeof(*rcmm), GFP_KERNEL);
+	if (!rcmm)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, rcmm);
+
+	rcmm->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(rcmm->base))
+		return PTR_ERR(rcmm->base);
+
+	pm_runtime_enable(&pdev->dev);
+
+	return 0;
+}
+
+static int rcar_cmm_remove(struct platform_device *pdev)
+{
+	pm_runtime_disable(&pdev->dev);
+
+	return 0;
+}
+
+static const struct of_device_id rcar_cmm_of_table[] = {
+	{ .compatible = "renesas,rcar-gen3-cmm", },
+	{ .compatible = "renesas,rcar-gen2-cmm", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, rcar_cmm_of_table);
+
+static struct platform_driver rcar_cmm_platform_driver = {
+	.probe		= rcar_cmm_probe,
+	.remove		= rcar_cmm_remove,
+	.driver		= {
+		.name	= "rcar-cmm",
+		.of_match_table = rcar_cmm_of_table,
+	},
+};
+
+module_platform_driver(rcar_cmm_platform_driver);
+
+MODULE_AUTHOR("Jacopo Mondi <[e-mail]>");
+MODULE_DESCRIPTION("Renesas R-Car CMM Driver");
+MODULE_LICENSE("GPL v2");

drivers/gpu/drm/rcar-du/rcar_cmm.h

···
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * rcar_cmm.h -- R-Car Display Unit Color Management Module
+ *
+ * Copyright (C) 2019 Jacopo Mondi <[e-mail]>
+ */
+
+#ifndef __RCAR_CMM_H__
+#define __RCAR_CMM_H__
+
+#define CM2_LUT_SIZE		256
+
+struct drm_color_lut;
+struct platform_device;
+
+/**
+ * struct rcar_cmm_config - CMM configuration
+ *
+ * @lut:	1D-LUT configuration
+ * @lut.table:	1D-LUT table entries. Disable LUT operations when NULL
+ */
+struct rcar_cmm_config {
+	struct {
+		struct drm_color_lut *table;
+	} lut;
+};
+
+#if IS_ENABLED(CONFIG_DRM_RCAR_CMM)
+int rcar_cmm_init(struct platform_device *pdev);
+
+int rcar_cmm_enable(struct platform_device *pdev);
+void rcar_cmm_disable(struct platform_device *pdev);
+
+int rcar_cmm_setup(struct platform_device *pdev,
+		   const struct rcar_cmm_config *config);
+#else
+static inline int rcar_cmm_init(struct platform_device *pdev)
+{
+	return -ENODEV;
+}
+
+static inline int rcar_cmm_enable(struct platform_device *pdev)
+{
+	return 0;
+}
+
+static inline void rcar_cmm_disable(struct platform_device *pdev)
+{
+}
+
+static inline int rcar_cmm_setup(struct platform_device *pdev,
+				 const struct rcar_cmm_config *config)
+{
+	return 0;
+}
+#endif /* IS_ENABLED(CONFIG_DRM_RCAR_CMM) */
+
+#endif /* __RCAR_CMM_H__ */