Re: [PATCH v4 3/9] drm: rcar-du: Add support for CMM

[Laurent Pinchart]

Hi Jacopo,

Thank you for the patch.

On Fri, Sep 06, 2019 at 03:54:30PM +0200, Jacopo Mondi wrote:
> 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 feature will be
> implemented on top of this basic one.
> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas@xxxxxxxxxx>
> ---
>  drivers/gpu/drm/rcar-du/Kconfig    |   7 +
>  drivers/gpu/drm/rcar-du/Makefile   |   1 +
>  drivers/gpu/drm/rcar-du/rcar_cmm.c | 251 +++++++++++++++++++++++++++++
>  drivers/gpu/drm/rcar-du/rcar_cmm.h |  61 +++++++
>  4 files changed, 320 insertions(+)
>  create mode 100644 drivers/gpu/drm/rcar-du/rcar_cmm.c
>  create mode 100644 drivers/gpu/drm/rcar-du/rcar_cmm.h
> 
> diff --git a/drivers/gpu/drm/rcar-du/Kconfig b/drivers/gpu/drm/rcar-du/Kconfig
> index 1529849e217e..539d232790d1 100644
> --- a/drivers/gpu/drm/rcar-du/Kconfig
> +++ b/drivers/gpu/drm/rcar-du/Kconfig
> @@ -13,6 +13,13 @@ config DRM_RCAR_DU
>  	  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
> +	bool "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"
>  	depends on DRM && OF
> diff --git a/drivers/gpu/drm/rcar-du/Makefile b/drivers/gpu/drm/rcar-du/Makefile
> index 6c2ed9c46467..4d1187ccc3e5 100644
> --- a/drivers/gpu/drm/rcar-du/Makefile
> +++ b/drivers/gpu/drm/rcar-du/Makefile
> @@ -15,6 +15,7 @@ rcar-du-drm-$(CONFIG_DRM_RCAR_LVDS)	+= rcar_du_of.o \
>  rcar-du-drm-$(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
> diff --git a/drivers/gpu/drm/rcar-du/rcar_cmm.c b/drivers/gpu/drm/rcar-du/rcar_cmm.c
> new file mode 100644
> index 000000000000..3cacdc4474c7
> --- /dev/null
> +++ b/drivers/gpu/drm/rcar-du/rcar_cmm.c
> @@ -0,0 +1,251 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * rcar_cmm.c -- R-Car Display Unit Color Management Module
> + *
> + * Copyright (C) 2019 Jacopo Mondi <jacopo+renesas@xxxxxxxxxx>
> + */
> +
> +#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;
> +	bool enabled;
> +
> +	/*
> +	 * @lut:		1D-LUT status
> +	 * @lut.enabled:	1D-LUT enabled flag
> +	 * @lut.table:		Table of 1D-LUT entries scaled to hardware
> +	 *			precision (8-bits per color component)
> +	 */
> +	struct {
> +		bool enabled;
> +		u32 table[CM2_LUT_SIZE];
> +	} 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_extract() - Scale down to hardware precision the DRM LUT table
> + *			    entries and store them.

"Scale the DRM LUT table entries to hardware precision and store them."

> + * @rcmm: Pointer to the CMM device
> + * @drm_lut: Pointer to the DRM LUT table
> + */
> +static void rcar_cmm_lut_extract(struct rcar_cmm *rcmm,
> +				 const struct drm_color_lut *drm_lut)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < CM2_LUT_SIZE; ++i) {
> +		const struct drm_color_lut *lut = &drm_lut[i];
> +
> +		rcmm->lut.table[i] = drm_color_lut_extract(lut->red, 8) << 16
> +				   | drm_color_lut_extract(lut->green, 8) << 8
> +				   | drm_color_lut_extract(lut->blue, 8);
> +	}
> +}
> +
> +/*
> + * rcar_cmm_lut_write() - Write to hardware the LUT table entries from the
> + *			  local table.

"Write the LUT table entries from the local table to the hardware."

> + * @rcmm: Pointer to the CMM device
> + */
> +static void rcar_cmm_lut_write(struct rcar_cmm *rcmm)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < CM2_LUT_SIZE; ++i)
> +		rcar_cmm_write(rcmm, CM2_LUT_TBL(i), rcmm->lut.table[i]);
> +}
> +
> +/*
> + * rcar_cmm_setup() - Configure the CMM unit.
> + * @pdev: The platform device associated with the CMM instance
> + * @config: The CRTC-provided configuration.
> + *
> + * Configure the CMM unit with the CRTC-provided configuration.
> + * Currently enabling, disabling and programming of the 1-D LUT unit is
> + * supported.
> + */
> +int rcar_cmm_setup(struct platform_device *pdev,
> +		   const struct rcar_cmm_config *config)
> +{
> +	struct rcar_cmm *rcmm = platform_get_drvdata(pdev);
> +
> +	/*
> +	 * As rcar_cmm_setup() is called by atomic commit tail helper, it might
> +	 * be called when the CMM is disabled. As we can't program the hardware
> +	 * in that case, store the configuration internally and apply it when
> +	 * the CMM will be enabled by the CRTC through rcar_cmm_enable().
> +	 */
> +	if (!rcmm->enabled) {
> +		if (!config->lut.enable)
> +			return 0;
> +
> +		rcar_cmm_lut_extract(rcmm, config->lut.table);
> +		rcmm->lut.enabled = true;
> +
> +		return 0;
> +	}
> +
> +	/* Stop LUT operations if requested. */
> +	if (!config->lut.enable) {
> +		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.
> +	 *
> +	 * FIXME: In order to have stable operations it is required to first
> +	 * enable the 1D-LUT and then program its table entries. This seems to
> +	 * contradict what the chip manual reports, and will have to be
> +	 * reconsidered when implementing support for double buffering.
> +	 */
> +	if (!rcmm->lut.enabled) {
> +		rcar_cmm_write(rcmm, CM2_LUT_CTRL, CM2_LUT_CTRL_LUT_EN);
> +		rcmm->lut.enabled = true;
> +	}
> +
> +	rcar_cmm_lut_extract(rcmm, config->lut.table);
> +	rcar_cmm_lut_write(rcmm);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(rcar_cmm_setup);
> +
> +/*
> + * rcar_cmm_enable() - Enable the CMM unit.
> + * @pdev: The platform device associated with the CMM instance
> + *
> + * Enable the CMM unit by enabling the parent clock and enabling the CMM
> + * components, such as 1-D LUT, if requested.
> + */
> +int rcar_cmm_enable(struct platform_device *pdev)
> +{
> +	struct rcar_cmm *rcmm = platform_get_drvdata(pdev);
> +	int ret;
> +
> +	ret = pm_runtime_get_sync(&pdev->dev);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Apply the LUT table values saved at rcar_cmm_setup() time. */
> +	if (rcmm->lut.enabled) {
> +		rcar_cmm_write(rcmm, CM2_LUT_CTRL, CM2_LUT_CTRL_LUT_EN);
> +		rcar_cmm_lut_write(rcmm);
> +	}
> +
> +	rcmm->enabled = true;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(rcar_cmm_enable);
> +
> +/*
> + * rcar_cmm_disable() - Disable the CMM unit.
> + * @pdev: The platform device associated with the CMM instance
> + *
> + * Disable the CMM unit by stopping the parent clock.
> + */
> +void rcar_cmm_disable(struct platform_device *pdev)
> +{
> +	struct rcar_cmm *rcmm = platform_get_drvdata(pdev);
> +
> +	rcar_cmm_write(rcmm, CM2_LUT_CTRL, 0);
> +
> +	pm_runtime_put(&pdev->dev);
> +
> +	rcmm->lut.enabled = false;
> +	rcmm->enabled = false;
> +}
> +EXPORT_SYMBOL_GPL(rcar_cmm_disable);
> +
> +/*
> + * rcar_cmm_init() - Make sure the CMM has probed.

I would document this as "Intialize the CMM" to match the function name.
We may add more initialization in the future.

> + * @pdev: The platform device associated with the CMM instance
> + *
> + * Return: 0 if the CMM has probed, -EPROBE_DEFER otherwise

0 on success, -EPROBE_DEFER is the CMM isn't availablet yet

> + */
> +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 <jacopo+renesas@xxxxxxxxxx>");
> +MODULE_DESCRIPTION("Renesas R-Car CMM Driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/gpu/drm/rcar-du/rcar_cmm.h b/drivers/gpu/drm/rcar-du/rcar_cmm.h
> new file mode 100644
> index 000000000000..15a2c874b6a6
> --- /dev/null
> +++ b/drivers/gpu/drm/rcar-du/rcar_cmm.h
> @@ -0,0 +1,61 @@
> +/* SPDX-License-Identifier: GPL-2.0+ */
> +/*
> + * rcar_cmm.h -- R-Car Display Unit Color Management Module
> + *
> + * Copyright (C) 2019 Jacopo Mondi <jacopo+renesas@xxxxxxxxxx>
> + */
> +
> +#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.enable:	1D-LUT enable flag
> + * @lut.table:	1D-LUT table entries. Might be set to NULL when the CMM has to
> + *		be re-enabled but not re=programmed.

s/re=programmed/re-programmed/

As discussed offline this can't really happen as far as I can tell.
However, it will still be useful when we'll add CLU support, as then a
CLU reprogramming without a LUT reprogramming could happen.

I think we should make the documentation a bit clearer:

"1D-LUT table entries. Only valid when lut.enable is true, shall be NULL
otherwise. When non-NULL, the LUT table will be programmed with the new
values. Otherwise the LUT table will retain its previously programmed
values."

This being said, the code in rcar_cmm_setup() will crash if table is
NULL. I would either drop the option of table being NULL (and thus
update the documentation here) if you don't need this yet in the DU
driver, or fix rcar_cmm_setup(). You've posted enough versions of this
series in my opinion, so please pick the easiest option, and we'll
rework the code when adding CLU support anyway.

With those small issues fixes,

Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>

> + */
> +struct rcar_cmm_config {
> +	struct {
> +		bool enable;
> +		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 0;
> +}
> +
> +static inline int rcar_cmm_enable(struct platform_device *pdev)
> +{
> +	return 0;
> +}
> +
> +static inline void rcar_cmm_disable(struct platform_device *pdev)
> +{
> +}
> +
> +static 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__ */

-- 
Regards,

Laurent Pinchart