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Message-ID: <1532497379.9280.32.camel@mtksdaap41>
Subject: Re: [PATCH v1 11/15] drm/mediatek: add dummy buffer for RDMA memory
 mode
From:   CK Hu <ck.hu@mediatek.com>
To:     Stu Hsieh <stu.hsieh@mediatek.com>
CC:     Philipp Zabel <p.zabel@pengutronix.de>,
        David Airlie <airlied@linux.ie>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        <dri-devel@lists.freedesktop.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-mediatek@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>, <srv_heupstream@mediatek.com>
Date:   Wed, 25 Jul 2018 13:42:59 +0800
In-Reply-To: <1532420235-22268-12-git-send-email-stu.hsieh@mediatek.com>
References: <1532420235-22268-1-git-send-email-stu.hsieh@mediatek.com>
         <1532420235-22268-12-git-send-email-stu.hsieh@mediatek.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Hi, Stu:

On Tue, 2018-07-24 at 16:17 +0800, Stu Hsieh wrote:
> This patch add dummy buffer for RDMA memory mode
> 
> When display power on, the drm frame work would modeset and
> set up the display HW.
> 
> In this time, the RDMA would start wroking and read the data from memory.
> But, user space not send the data to drm yet.
> 
> For this case, if user space not send data to display hw(RDMA) yet,
> RDMA would read the wrong address to show garbage.
> 
> Therefore, we create dummy buffer for RDMA reading memory
> when userspace not send the data yet.
> 

Is this the only solution? If panel resolution is 1920x1080, the buffer
size is 8294400 bytes. How large it is. If we have another solution,
I'll not accept this one. As far as I know, DSI or DPI could output
single color even though there is no input data. If this is true, when
encoder is enabled, it output the single color. When crtc enable, config
all setting except 'start'. When receive the buffer, 'start' the
pipeline which include encoder. When encoder 'start', it disable the
single color function and output the data from input.

Regards,
CK


> Signed-off-by: Stu Hsieh <stu.hsieh@mediatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_disp_rdma.c    | 23 +++++++++++++++++++++++
>  drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h |  1 +
>  2 files changed, 24 insertions(+)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
> index 8d41f5cd485b..e28f368728cd 100644
> --- a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
> +++ b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
> @@ -20,6 +20,7 @@
>  
>  #include "mtk_drm_crtc.h"
>  #include "mtk_drm_ddp_comp.h"
> +#include "mtk_drm_gem.h"
>  
>  #define DISP_REG_RDMA_INT_ENABLE		0x0000
>  #define DISP_REG_RDMA_INT_STATUS		0x0004
> @@ -59,6 +60,9 @@
>  #define MEM_MODE_INPUT_FORMAT_UYVY		(0x004 << 4)
>  #define MEM_MODE_INPUT_FORMAT_YUYV		(0x005 << 4)
>  
> +#define RDMA_DUMMY_BUFFER_SIZE(h, v)		((h) * (v) * 4)
> +#define RDMA_DUMMY_BUFFER_PITCH(h)		((h) * 4)
> +
>  struct mtk_disp_rdma_data {
>  	unsigned int fifo_size;
>  };
> @@ -74,6 +78,7 @@ struct mtk_disp_rdma {
>  	const struct mtk_disp_rdma_data	*data;
>  	struct drm_device *drm_dev;
>  	bool rdma_memory_mode;
> +	unsigned int dummy_size;
>  };
>  
>  static inline struct mtk_disp_rdma *comp_to_rdma(struct mtk_ddp_comp *comp)
> @@ -126,14 +131,29 @@ static void mtk_rdma_disable_vblank(struct mtk_ddp_comp *comp)
>  
>  static void mtk_rdma_start(struct mtk_ddp_comp *comp)
>  {
> +	struct mtk_disp_rdma *rdma = comp_to_rdma(comp);
> +	bool *rdma_memory_mode = comp->comp_mode;
> +
> +	if (*rdma_memory_mode == true) {
> +		comp->mtk_gem = mtk_drm_gem_create(rdma->drm_dev,
> +						   rdma->dummy_size, false);
> +		writel(comp->mtk_gem->dma_addr & 0xFFFFFFFF,
> +		       comp->regs + DISP_RDMA_MEM_START_ADDR);
> +	}
> +
>  	rdma_update_bits(comp, DISP_REG_RDMA_GLOBAL_CON, RDMA_ENGINE_EN,
>  			 RDMA_ENGINE_EN);
>  }
>  
>  static void mtk_rdma_stop(struct mtk_ddp_comp *comp)
>  {
> +	bool *rdma_memory_mode = comp->comp_mode;
> +
>  	writel(RDMA_SOFT_RESET, comp->regs + DISP_REG_RDMA_GLOBAL_CON);
>  	writel(0, comp->regs + DISP_REG_RDMA_GLOBAL_CON);
> +
> +	if (*rdma_memory_mode == true)
> +		mtk_drm_gem_free_object(&comp->mtk_gem->base);
>  }
>  
>  static void mtk_rdma_config(struct mtk_ddp_comp *comp, unsigned int width,
> @@ -149,8 +169,11 @@ static void mtk_rdma_config(struct mtk_ddp_comp *comp, unsigned int width,
>  	rdma_update_bits(comp, DISP_REG_RDMA_SIZE_CON_1, 0xfffff, height);
>  
>  	if (*rdma_memory_mode == true) {
> +		rdma->dummy_size = RDMA_DUMMY_BUFFER_SIZE(width, height);
>  		rdma_update_bits(comp, DISP_REG_RDMA_SIZE_CON_0, 0xff0000,
>  				 MATRIX_INT_MTX_SEL_DEFAULT);
> +		writel(RDMA_DUMMY_BUFFER_PITCH(width),
> +		       comp->regs + DISP_RDMA_MEM_SRC_PITCH);
>  		rdma_update_bits(comp, DISP_REG_RDMA_GLOBAL_CON,
>  				 RDMA_MODE_MEMORY, RDMA_MODE_MEMORY);
>  	}
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h
> index a1988ce15141..6dbb83144a74 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h
> @@ -92,6 +92,7 @@ struct mtk_ddp_comp {
>  	int irq;
>  	struct device *larb_dev;
>  	enum mtk_ddp_comp_id id;
> +	struct mtk_drm_gem_obj *mtk_gem;
>  	const struct mtk_ddp_comp_funcs *funcs;
>  	void *comp_mode;
>  };