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Reply-To: kieran.bingham+renesas@ideasonboard.com
Subject: Re: [PATCH v4 3/9] drm: rcar-du: Add support for CMM
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Jacopo Mondi <jacopo+renesas@jmondi.org>
Cc:     geert@linux-m68k.org, horms@verge.net.au, uli+renesas@fpond.eu,
        VenkataRajesh.Kalakodima@in.bosch.com, airlied@linux.ie,
        daniel@ffwll.ch, koji.matsuoka.xm@renesas.com, muroya@ksk.co.jp,
        Harsha.ManjulaMallikarjun@in.bosch.com,
        linux-renesas-soc@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org
References: <20190906135436.10622-1-jacopo+renesas@jmondi.org>
 <20190906135436.10622-4-jacopo+renesas@jmondi.org>
 <20190918225534.GA11474@pendragon.ideasonboard.com>
From:   Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Organization: Ideas on Board
Message-ID: <48b1333a-74e4-34b8-f898-79a74a88a816@ideasonboard.com>
Date:   Thu, 19 Sep 2019 09:59:39 +0100
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Hi Jacopo, Laurent,


On 18/09/2019 23:55, Laurent Pinchart wrote:
> 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@jmondi.org>
>> ---
>>  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@jmondi.org>
>> + */
>> +
>> +#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@jmondi.org>");
>> +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@jmondi.org>
>> + */
>> +
>> +#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@ideasonboard.com>
> 
>> + */
>> +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. ...

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

--
Kieran


>> +}
>> +
>> +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__ */
>