linux-kernel - Re: [PATCH v1, 2/2] drm/mediatek: Fix external display vblank timeout issue

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Date:   Tue, 3 Dec 2019 15:07:11 +0800
From:   CK Hu <ck.hu@...iatek.com>
To:     <yongqiang.niu@...iatek.com>
CC:     Philipp Zabel <p.zabel@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "David Airlie" <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Mark Rutland <mark.rutland@....com>,
        <dri-devel@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v1, 2/2] drm/mediatek: Fix external display vblank
 timeout issue

Hi, Yongqiang:

I would like the title could clearly express what does this patch do. I
think what this patch do is to implement prepare/unprepare interface for
dpi driver. And you could describe why do this in commit message.


On Wed, 2019-11-27 at 09:17 +0800, yongqiang.niu@...iatek.com wrote:
> From: Yongqiang Niu <yongqiang.niu@...iatek.com>
> 
> Fix external display vblank timeout issue

I think you move dpi_power_on to more early stage. But why this would
fix vblank timeout. Please describe more about this so that I would
agree this patch. 

This is a bug fix, so please add a 'Fixes' tag.

> 
> Signed-off-by: Yongqiang Niu <yongqiang.niu@...iatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_dpi.c          | 14 +++++++++-----
>  drivers/gpu/drm/mediatek/mtk_drm_crtc.c     |  6 ++++++
>  drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h | 14 ++++++++++++++
>  3 files changed, 29 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dpi.c b/drivers/gpu/drm/mediatek/mtk_dpi.c
> index be6d95c..38cabbe 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dpi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dpi.c
> @@ -387,8 +387,12 @@ static int mtk_dpi_power_on(struct mtk_dpi *dpi)
>  {
>  	int ret;
>  
> -	if (++dpi->refcount != 1)
> +	if (++dpi->refcount != 1) {
> +		dev_warn(dpi->dev, "%s refcount: %d\n", __func__, dpi->refcount);
>  		return 0;
> +	}
> +
> +	DRM_DEBUG_DRIVER("%s refcount %d\n", __func__, dpi->refcount);
>  
>  	ret = clk_prepare_enable(dpi->engine_clk);
>  	if (ret) {
> @@ -563,14 +567,14 @@ static int mtk_dpi_atomic_check(struct drm_encoder *encoder,
>  	.atomic_check = mtk_dpi_atomic_check,
>  };
>  
> -static void mtk_dpi_start(struct mtk_ddp_comp *comp)
> +static void mtk_dpi_prepare(struct mtk_ddp_comp *comp)
>  {
>  	struct mtk_dpi *dpi = container_of(comp, struct mtk_dpi, ddp_comp);
>  
>  	mtk_dpi_power_on(dpi);
>  }
>  
> -static void mtk_dpi_stop(struct mtk_ddp_comp *comp)
> +static void mtk_dpi_unprepare(struct mtk_ddp_comp *comp)
>  {
>  	struct mtk_dpi *dpi = container_of(comp, struct mtk_dpi, ddp_comp);
>  
> @@ -578,8 +582,8 @@ static void mtk_dpi_stop(struct mtk_ddp_comp *comp)
>  }
>  
>  static const struct mtk_ddp_comp_funcs mtk_dpi_funcs = {
> -	.start = mtk_dpi_start,
> -	.stop = mtk_dpi_stop,
> +	.prepare = mtk_dpi_prepare,
> +	.unprepare = mtk_dpi_unprepare,
>  };
>  
>  static int mtk_dpi_bind(struct device *dev, struct device *master, void *data)
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> index 7eca02f..a6d3d97 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> @@ -345,6 +345,9 @@ static int mtk_crtc_ddp_hw_init(struct mtk_drm_crtc *mtk_crtc)
>  		return ret;
>  	}
>  
> +	for (i = 0; i < mtk_crtc->ddp_comp_nr; i++)
> +		mtk_ddp_comp_prepare(mtk_crtc->ddp_comp[i]);
> +
>  	ret = mtk_disp_mutex_prepare(mtk_crtc->mutex);
>  	if (ret < 0) {
>  		DRM_ERROR("Failed to enable mutex clock: %d\n", ret);
> @@ -434,6 +437,9 @@ static void mtk_crtc_ddp_hw_fini(struct mtk_drm_crtc *mtk_crtc)
>  	mtk_crtc_ddp_clk_disable(mtk_crtc);
>  	mtk_disp_mutex_unprepare(mtk_crtc->mutex);
>  
> +	for (i = 0; i < mtk_crtc->ddp_comp_nr; i++)
> +		mtk_ddp_comp_unprepare(mtk_crtc->ddp_comp[i]);
> +
>  	pm_runtime_put(drm->dev);
>  
>  	if (crtc->state->event && !crtc->state->active) {
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h
> index 5b0a3d4..097b90d 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h
> @@ -78,6 +78,8 @@ struct mtk_ddp_comp_funcs {
>  	void (*stop)(struct mtk_ddp_comp *comp);
>  	void (*enable_vblank)(struct mtk_ddp_comp *comp, struct drm_crtc *crtc);
>  	void (*disable_vblank)(struct mtk_ddp_comp *comp);
> +	void (*prepare)(struct mtk_ddp_comp *comp);
> +	void (*unprepare)(struct mtk_ddp_comp *comp);
>  	unsigned int (*supported_rotations)(struct mtk_ddp_comp *comp);
>  	unsigned int (*layer_nr)(struct mtk_ddp_comp *comp);
>  	void (*layer_on)(struct mtk_ddp_comp *comp, unsigned int idx,
> @@ -117,6 +119,18 @@ static inline void mtk_ddp_comp_config(struct mtk_ddp_comp *comp,
>  		comp->funcs->config(comp, w, h, vrefresh, bpc, cmdq_pkt);
>  }
>  
> +static inline void mtk_ddp_comp_prepare(struct mtk_ddp_comp *comp)
> +{
> +	if (comp->funcs && comp->funcs->prepare)
> +		comp->funcs->prepare(comp);
> +}
> +
> +static inline void mtk_ddp_comp_unprepare(struct mtk_ddp_comp *comp)
> +{
> +	if (comp->funcs && comp->funcs->unprepare)
> +		comp->funcs->unprepare(comp);
> +}
> +
>  static inline void mtk_ddp_comp_start(struct mtk_ddp_comp *comp)
>  {
>  	if (comp->funcs && comp->funcs->start)