Re: [PATCH v3 08/14] drm: rcar-du: Add support for CMM

[Laurent Pinchart]

Hi Jacopo,

Thank you for the patch.

On Sun, Aug 25, 2019 at 03:51:48PM +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 | 262 +++++++++++++++++++++++++++++
>  drivers/gpu/drm/rcar-du/rcar_cmm.h |  38 +++++
>  4 files changed, 308 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..55361f5701e8
> --- /dev/null
> +++ b/drivers/gpu/drm/rcar-du/rcar_cmm.c
> @@ -0,0 +1,262 @@
> +// 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.size:		Number of entries in the LUT table

Please see my review of patch 13/14, I wonder if we could drop this
field.

> +	 * @lut.table:		Table of 1D-LUT entries scaled to HW support
> +	 *			precision (8-bits per color component)
> +	 */
> +	struct {
> +		bool enabled;
> +		unsigned int size;
> +		u32 table[CMM_GAMMA_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 hw precision the DRM LUT table

s/hw/hardware/ (and below too)

> + *			    entries and store them.
> + * @rcmm: Pointer to the CMM device
> + * @size: Number of entries in the table
> + * @drm_lut: DRM LUT table
> + */
> +static void rcar_cmm_lut_extract(struct rcar_cmm *rcmm, size_t size,
> +				 const struct drm_color_lut *drm_lut)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < 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);
> +	}
> +
> +	rcmm->lut.size = size;
> +}
> +
> +/*
> + * rcar_cmm_lut_load() - Write to hw the LUT table entries from the local table.
> + *

No need for a blank line

> + * @rcmm: Pointer to the CMM device
> + */
> +static void rcar_cmm_lut_load(struct rcar_cmm *rcmm)

I would name this rcar_cmm_lut_write().

> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < rcmm->lut.size; ++i) {
> +		u32 entry = rcmm->lut.table[i];
> +
> +		rcar_cmm_write(rcmm, CM2_LUT_TBL(i), entry);

You don't need the local entry variable.

> +	}
> +}
> +
> +/**
> + * rcar_cmm_setup() - configure the CMM unit

s/configure/Configure/ and s/$/./, or the other way around for the other
functions (I don't mine which one, but let's stay consistent).

> + *

No need for a blank line (same for the functions below).

> + * @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);
> +
> +	if (config->lut.size > CMM_GAMMA_LUT_SIZE)
> +		return -EINVAL;
> +
> +	/*
> +	 * 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.size, 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;
> +			rcmm->lut.size = 0;
> +		}
> +
> +		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.size, config->lut.table);
> +	rcar_cmm_lut_load(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;
> +
> +	if (!rcmm)
> +		return -EPROBE_DEFER;

This function is called in rcar_du_crtc_atomic_enable(), so that's not
the right error code. It seems we need another function for the CMM API
to defer probing :-/ I would call it rcar_cmm_init(). This check would
then be removed.

> +
> +	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_load(rcmm);

You will not like this, but I just realised that we're now reprogramming
the LUT contents every time the CMM is enabled. Do you think that's
something we should optimise ? And yes, that would require introducing
back an update flag in rcmm->lut :-S Sorry for not realising this when I
proposed dropping it.

> +	}
> +
> +	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->lut.size = 0;
> +
> +	rcmm->enabled = false;
> +}
> +EXPORT_SYMBOL_GPL(rcar_cmm_disable);
> +
> +static int rcar_cmm_probe(struct platform_device *pdev)
> +{
> +	struct rcar_cmm *rcmm;
> +	struct resource *res;
> +
> +	rcmm = devm_kzalloc(&pdev->dev, sizeof(*rcmm), GFP_KERNEL);
> +	if (!rcmm)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, rcmm);
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	rcmm->base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(rcmm->base))
> +		return PTR_ERR(rcmm->base);

You really don't like combining those two calls, do you ? :-)

> +
> +	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,cmm-r8a7795", },
> +	{ .compatible = "renesas,cmm-r8a7796", },
> +	{ .compatible = "renesas,cmm-r8a77965", },
> +	{ .compatible = "renesas,cmm-r8a77990", },
> +	{ .compatible = "renesas,cmm-r8a77995", },

As Geert pointed out, I would drop those entries.

> +	{ .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..b0bb7349ebaa
> --- /dev/null
> +++ b/drivers/gpu/drm/rcar-du/rcar_cmm.h
> @@ -0,0 +1,38 @@
> +/* 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 CMM_GAMMA_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
> + * @lut.size:	Number of 1D-LUT (max 256)

s/1D-LUT/1D-LUT entries/

> + */
> +struct rcar_cmm_config {
> +	struct {
> +		bool enable;
> +		struct drm_color_lut *table;
> +		unsigned int size;
> +	} lut;
> +};
> +
> +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);
> +
> +#endif /* __RCAR_CMM_H__ */

-- 
Regards,

Laurent Pinchart