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

[Laurent Pinchart]

Hi Kieran,

On Thu, Sep 19, 2019 at 09:59:39AM +0100, Kieran Bingham wrote:
> On 18/09/2019 23:55, Laurent Pinchart wrote:
> > 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
> 
> And possibly -ENODEV if the suggestion below in the header is worthy, to
> return no device if the CMM is disabled at the CONFIG_ level.
> 
> >> + */
> >> +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;
> 
> I feel like here, this should return -ENODEV if CMM is disabled, and
> allow rcar_du_cmm_init() to succeed, but leave the rcdu->cmms[i]
> unpopulated. ...

I think that's a good idea, otherwise the DU driver will believe that
CMM initialisation succeeded, and will configure the DU to route its
outputs to the CMM. I don't think that would work nicely without a
driver :-) Although, in practice, for the processing (non-statistics)
path, the DU output clock may be all that is needed, so the CMM might be
operational in its default configuration without the MSTP clock. Still,
that's probably not a very safe path, so I'd rather see CMM being
disabled on the DU side in that case.

> But this could be updated later too if it's awkward ...

Hopefully that would be easy to do :-)

> >> +}
> >> +
> >> +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