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Date:   Wed, 9 Oct 2019 14:01:36 -0400
From:   Sean Paul <sean@poorly.run>
To:     Ezequiel Garcia <ezequiel@collabora.com>
Cc:     dri-devel@lists.freedesktop.org,
        linux-rockchip@lists.infradead.org,
        Heiko =?iso-8859-1?Q?St=FCbner?= <heiko@sntech.de>,
        Sandy Huang <hjc@rock-chips.com>, kernel@collabora.com,
        Sean Paul <seanpaul@chromium.org>,
        Boris Brezillon <boris.brezillon@collabora.com>,
        Douglas Anderson <dianders@chromium.org>,
        Jacopo Mondi <jacopo@jmondi.org>,
        Ilia Mirkin <imirkin@alum.mit.edu>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 2/3] drm/rockchip: Add optional support for CRTC gamma
 LUT
Message-ID: <20191009180136.GE85762@art_vandelay>
References: <20191008230038.24037-1-ezequiel@collabora.com>
 <20191008230038.24037-3-ezequiel@collabora.com>
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In-Reply-To: <20191008230038.24037-3-ezequiel@collabora.com>
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Sender: linux-kernel-owner@vger.kernel.org
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On Tue, Oct 08, 2019 at 08:00:37PM -0300, Ezequiel Garcia wrote:
> Add an optional CRTC gamma LUT support, and enable it on RK3288.
> This is currently enabled via a separate address resource,
> which needs to be specified in the devicetree.
> 
> The address resource is required because on some SoCs, such as
> RK3288, the LUT address is after the MMU address, and the latter
> is supported by a different driver. This prevents the DRM driver
> from requesting an entire register space.
> 
> The current implementation works for RGB 10-bit tables, as that
> is what seems to work on RK3288.
> 
> Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>

Hey Ezequiel,
Just a few comments on the actual content of the patch as opposed to my higher
level comments yesterday. I think we're almost there, thanks for sticking this
out!

> ---
> Changes from v3:
> * Move to atomic_enable and atomic_begin,
>   as discussed with Sean Paul.
> * Dropped the Reviewed-bys.
> Changes from v2:
> * None.
> Changes from v1:
> * drop explicit linear LUT after finding a proper
>   way to disable gamma correction.
> * avoid setting gamma is the CRTC is not active.
> * s/int/unsigned int as suggested by Jacopo.
> * only enable color management and set gamma size
>   if gamma LUT is supported, suggested by Doug.
> * drop the reg-names usage, and instead just use indexed reg
>   specifiers, suggested by Doug.
> Changes from RFC:
> * Request (an optional) address resource for the LUT.
> * Drop support for RK3399, which doesn't seem to work
>   out of the box and needs more research.
> * Support pass-thru setting when GAMMA_LUT is NULL.
> * Add a check for the gamma size, as suggested by Ilia.
> * Move gamma setting to atomic_commit_tail, as pointed
>   out by Jacopo/Laurent, is the correct way.
> ---
>  drivers/gpu/drm/rockchip/rockchip_drm_fb.c  |   1 +
>  drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 125 ++++++++++++++++++++
>  drivers/gpu/drm/rockchip/rockchip_drm_vop.h |   5 +
>  drivers/gpu/drm/rockchip/rockchip_vop_reg.c |   2 +
>  4 files changed, 133 insertions(+)
> 
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
> index ca01234c037c..697ee04b85cf 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
> @@ -17,6 +17,7 @@
>  #include "rockchip_drm_drv.h"
>  #include "rockchip_drm_fb.h"
>  #include "rockchip_drm_gem.h"
> +#include "rockchip_drm_vop.h"

Leftover from the previous version?

>  
>  static const struct drm_framebuffer_funcs rockchip_drm_fb_funcs = {
>  	.destroy       = drm_gem_fb_destroy,
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> index 613404f86668..85c1269a1218 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> @@ -139,6 +139,7 @@ struct vop {
>  
>  	uint32_t *regsbak;
>  	void __iomem *regs;
> +	void __iomem *lut_regs;
>  
>  	/* physical map length of vop register */
>  	uint32_t len;
> @@ -1048,6 +1049,84 @@ static bool vop_crtc_mode_fixup(struct drm_crtc *crtc,
>  	return true;
>  }
>  
> +static bool vop_dsp_lut_is_enable(struct vop *vop)

*enabled

> +{
> +	return vop_read_reg(vop, 0, &vop->data->common->dsp_lut_en);
> +}
> +
> +static void vop_crtc_write_gamma_lut(struct vop *vop, struct drm_crtc *crtc)
> +{
> +	struct drm_color_lut *lut = crtc->state->gamma_lut->data;
> +	unsigned int i;
> +
> +	for (i = 0; i < crtc->gamma_size; i++) {
> +		u32 word;
> +
> +		word = (drm_color_lut_extract(lut[i].red, 10) << 20) |
> +		       (drm_color_lut_extract(lut[i].green, 10) << 10) |
> +			drm_color_lut_extract(lut[i].blue, 10);
> +		writel(word, vop->lut_regs + i * 4);
> +	}
> +}
> +
> +static void vop_crtc_gamma_set(struct vop *vop, struct drm_crtc *crtc,
> +			       struct drm_crtc_state *old_crtc_state)
> +{
> +	unsigned int idle;
> +	int ret;
> +

How about:

        if (!vop->lut_regs)
                return;

here and then you can remove that condition above the 2 callsites

> +	/*
> +	 * In order to write the LUT to the internal memory,
> +	 * we need to first make sure the dsp_lut_en bit is cleared.
> +	 */
> +	spin_lock(&vop->reg_lock);
> +	VOP_REG_SET(vop, common, dsp_lut_en, 0);
> +	vop_cfg_done(vop);
> +	spin_unlock(&vop->reg_lock);
> +
> +	/*
> +	 * If the CRTC is not active, dsp_lut_en will not get cleared.
> +	 * Apparently we still need to do the above step to for
> +	 * gamma correction to be disabled.
> +	 */
> +	if (!crtc->state->active)
> +		return;
> +
> +	ret = readx_poll_timeout(vop_dsp_lut_is_enable, vop,
> +				 idle, !idle, 5, 30 * 1000);
> +	if (ret) {
> +		DRM_DEV_ERROR(vop->dev, "display LUT RAM enable timeout!\n");
> +		return;
> +	}
> +
> +	if (crtc->state->gamma_lut &&
> +	   (!old_crtc_state->gamma_lut || (crtc->state->gamma_lut->base.id !=
> +					old_crtc_state->gamma_lut->base.id))) {

Silly question, but isn't the second part of this check redundant since you need 
color_mgmt_changed || active_changed to get into this function?

So maybe invert the conditional here and exit early (to save a level of
indentation in the block below):

        if (!crtc->state->gamma_lut)
                return;

        spin_lock(&vop->reg_lock);

        vop_crtc_write_gamma_lut(vop, crtc);
        VOP_REG_SET(vop, common, dsp_lut_en, 1);
        vop_cfg_done(vop);

        spin_unlock(&vop->reg_lock);

> +
> +		spin_lock(&vop->reg_lock);
> +
> +		vop_crtc_write_gamma_lut(vop, crtc);
> +		VOP_REG_SET(vop, common, dsp_lut_en, 1);
> +		vop_cfg_done(vop);
> +
> +		spin_unlock(&vop->reg_lock);
> +	}
> +}
> +
> +static void vop_crtc_atomic_begin(struct drm_crtc *crtc,
> +				   struct drm_crtc_state *old_crtc_state)
> +{
> +	struct vop *vop = to_vop(crtc);
> +
> +	/*
> +	 * Only update GAMMA if the 'active' flag is not changed,
> +	 * otherwise it's updated by .atomic_enable.
> +	 */
> +	if (vop->lut_regs && crtc->state->color_mgmt_changed &&
> +	    !crtc->state->active_changed)
> +		vop_crtc_gamma_set(vop, crtc, old_crtc_state);
> +}
> +
>  static void vop_crtc_atomic_enable(struct drm_crtc *crtc,
>  				   struct drm_crtc_state *old_state)
>  {
> @@ -1075,6 +1154,14 @@ static void vop_crtc_atomic_enable(struct drm_crtc *crtc,
>  		return;
>  	}
>  
> +	/*
> +	 * If we have a GAMMA LUT in the state, then let's make sure
> +	 * it's updated. We might be coming out of suspend,
> +	 * which means the LUT internal memory needs to be re-written.
> +	 */
> +	if (vop->lut_regs && crtc->state->gamma_lut)
> +		vop_crtc_gamma_set(vop, crtc, old_state);
> +
>  	mutex_lock(&vop->vop_lock);
>  
>  	WARN_ON(vop->event);
> @@ -1191,6 +1278,26 @@ static void vop_wait_for_irq_handler(struct vop *vop)
>  	synchronize_irq(vop->irq);
>  }
>  
> +static int vop_crtc_atomic_check(struct drm_crtc *crtc,
> +				 struct drm_crtc_state *crtc_state)
> +{
> +	struct vop *vop = to_vop(crtc);
> +
> +	if (vop->lut_regs && crtc_state->color_mgmt_changed &&
> +	    crtc_state->gamma_lut) {
> +		unsigned int len;
> +
> +		len = drm_color_lut_size(crtc_state->gamma_lut);
> +		if (len != crtc->gamma_size) {
> +			DRM_DEBUG_KMS("Invalid LUT size; got %d, expected %d\n",
> +				      len, crtc->gamma_size);
> +			return -EINVAL;
> +		}

Overflow is avoided in drm_mode_gamma_set_ioctl(), so I don't think you need
this function.

Sean

> +	}
> +
> +	return 0;
> +}
> +
>  static void vop_crtc_atomic_flush(struct drm_crtc *crtc,
>  				  struct drm_crtc_state *old_crtc_state)
>  {
> @@ -1243,6 +1350,8 @@ static void vop_crtc_atomic_flush(struct drm_crtc *crtc,
>  
>  static const struct drm_crtc_helper_funcs vop_crtc_helper_funcs = {
>  	.mode_fixup = vop_crtc_mode_fixup,
> +	.atomic_check = vop_crtc_atomic_check,
> +	.atomic_begin = vop_crtc_atomic_begin,
>  	.atomic_flush = vop_crtc_atomic_flush,
>  	.atomic_enable = vop_crtc_atomic_enable,
>  	.atomic_disable = vop_crtc_atomic_disable,
> @@ -1361,6 +1470,7 @@ static const struct drm_crtc_funcs vop_crtc_funcs = {
>  	.disable_vblank = vop_crtc_disable_vblank,
>  	.set_crc_source = vop_crtc_set_crc_source,
>  	.verify_crc_source = vop_crtc_verify_crc_source,
> +	.gamma_set = drm_atomic_helper_legacy_gamma_set,
>  };
>  
>  static void vop_fb_unref_worker(struct drm_flip_work *work, void *val)
> @@ -1518,6 +1628,10 @@ static int vop_create_crtc(struct vop *vop)
>  		goto err_cleanup_planes;
>  
>  	drm_crtc_helper_add(crtc, &vop_crtc_helper_funcs);
> +	if (vop->lut_regs) {
> +		drm_mode_crtc_set_gamma_size(crtc, vop_data->lut_size);
> +		drm_crtc_enable_color_mgmt(crtc, 0, false, vop_data->lut_size);
> +	}
>  
>  	/*
>  	 * Create drm_planes for overlay windows with possible_crtcs restricted
> @@ -1822,6 +1936,17 @@ static int vop_bind(struct device *dev, struct device *master, void *data)
>  	if (IS_ERR(vop->regs))
>  		return PTR_ERR(vop->regs);
>  
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> +	if (res) {
> +		if (!vop_data->lut_size) {
> +			DRM_DEV_ERROR(dev, "no gamma LUT size defined\n");
> +			return -EINVAL;
> +		}
> +		vop->lut_regs = devm_ioremap_resource(dev, res);
> +		if (IS_ERR(vop->lut_regs))
> +			return PTR_ERR(vop->lut_regs);
> +	}
> +
>  	vop->regsbak = devm_kzalloc(dev, vop->len, GFP_KERNEL);
>  	if (!vop->regsbak)
>  		return -ENOMEM;
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.h b/drivers/gpu/drm/rockchip/rockchip_drm_vop.h
> index 2149a889c29d..8192c90d48c4 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.h
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.h
> @@ -7,6 +7,8 @@
>  #ifndef _ROCKCHIP_DRM_VOP_H
>  #define _ROCKCHIP_DRM_VOP_H
>  
> +#include <drm/drm_atomic.h>
> +
>  /*
>   * major: IP major version, used for IP structure
>   * minor: big feature change under same structure
> @@ -67,6 +69,7 @@ struct vop_common {
>  	struct vop_reg dither_down_mode;
>  	struct vop_reg dither_down_en;
>  	struct vop_reg dither_up;
> +	struct vop_reg dsp_lut_en;
>  	struct vop_reg gate_en;
>  	struct vop_reg mmu_en;
>  	struct vop_reg out_mode;
> @@ -170,6 +173,7 @@ struct vop_data {
>  	const struct vop_win_yuv2yuv_data *win_yuv2yuv;
>  	const struct vop_win_data *win;
>  	unsigned int win_size;
> +	unsigned int lut_size;
>  
>  #define VOP_FEATURE_OUTPUT_RGB10	BIT(0)
>  #define VOP_FEATURE_INTERNAL_RGB	BIT(1)
> @@ -373,4 +377,5 @@ static inline int scl_vop_cal_lb_mode(int width, bool is_yuv)
>  }
>  
>  extern const struct component_ops vop_component_ops;
> +
>  #endif /* _ROCKCHIP_DRM_VOP_H */
> diff --git a/drivers/gpu/drm/rockchip/rockchip_vop_reg.c b/drivers/gpu/drm/rockchip/rockchip_vop_reg.c
> index d1494be14471..42ddcb698c82 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_vop_reg.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_vop_reg.c
> @@ -598,6 +598,7 @@ static const struct vop_common rk3288_common = {
>  	.dither_down_en = VOP_REG(RK3288_DSP_CTRL1, 0x1, 2),
>  	.pre_dither_down = VOP_REG(RK3288_DSP_CTRL1, 0x1, 1),
>  	.dither_up = VOP_REG(RK3288_DSP_CTRL1, 0x1, 6),
> +	.dsp_lut_en = VOP_REG(RK3288_DSP_CTRL1, 0x1, 0),
>  	.data_blank = VOP_REG(RK3288_DSP_CTRL0, 0x1, 19),
>  	.dsp_blank = VOP_REG(RK3288_DSP_CTRL0, 0x3, 18),
>  	.out_mode = VOP_REG(RK3288_DSP_CTRL0, 0xf, 0),
> @@ -646,6 +647,7 @@ static const struct vop_data rk3288_vop = {
>  	.output = &rk3288_output,
>  	.win = rk3288_vop_win_data,
>  	.win_size = ARRAY_SIZE(rk3288_vop_win_data),
> +	.lut_size = 1024,
>  };
>  
>  static const int rk3368_vop_intrs[] = {
> -- 
> 2.22.0
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS