linux-kernel - Re: [PATCH v6, 13/14] drm/mediatek: add fifo

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Date:   Thu, 2 Jan 2020 15:31:57 +0800
From:   CK Hu <ck.hu@...iatek.com>
To:     Yongqiang Niu <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 v6, 13/14] drm/mediatek: add fifo_size into rdma private
 data

Hi, Yongqiang:

On Thu, 2020-01-02 at 13:42 +0800, Yongqiang Niu wrote:
> On Thu, 2020-01-02 at 13:20 +0800, CK Hu wrote:
> > Hi, Yongqiang:
> > 
> > On Thu, 2020-01-02 at 12:00 +0800, Yongqiang Niu wrote:
> > > the fifo size of rdma in mt8183 is different.
> > > rdma0 fifo size is 5k
> > > rdma1 fifo size is 2k
> > > 
> > > Signed-off-by: Yongqiang Niu <yongqiang.niu@...iatek.com>
> > > ---
> > >  drivers/gpu/drm/mediatek/mtk_disp_rdma.c | 21 ++++++++++++++++++++-
> > >  1 file changed, 20 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
> > > index 405afef..691480b 100644
> > > --- a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
> > > +++ b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
> > > @@ -62,6 +62,7 @@ struct mtk_disp_rdma {
> > >  	struct mtk_ddp_comp		ddp_comp;
> > >  	struct drm_crtc			*crtc;
> > >  	const struct mtk_disp_rdma_data	*data;
> > > +	u32				fifo_size;
> > >  };
> > >  
> > >  static inline struct mtk_disp_rdma *comp_to_rdma(struct mtk_ddp_comp *comp)
> > > @@ -130,10 +131,16 @@ static void mtk_rdma_config(struct mtk_ddp_comp *comp, unsigned int width,
> > >  	unsigned int threshold;
> > >  	unsigned int reg;
> > >  	struct mtk_disp_rdma *rdma = comp_to_rdma(comp);
> > > +	u32 rdma_fifo_size;
> > >  
> > >  	rdma_update_bits(comp, DISP_REG_RDMA_SIZE_CON_0, 0xfff, width);
> > >  	rdma_update_bits(comp, DISP_REG_RDMA_SIZE_CON_1, 0xfffff, height);
> > >  
> > > +	if (rdma->fifo_size)
> > > +		rdma_fifo_size = rdma->fifo_size;
> > > +	else
> > > +		rdma_fifo_size = RDMA_FIFO_SIZE(rdma);
> > > +
> > >  	/*
> > >  	 * Enable FIFO underflow since DSI and DPI can't be blocked.
> > >  	 * Keep the FIFO pseudo size reset default of 8 KiB. Set the
> > > @@ -142,7 +149,7 @@ static void mtk_rdma_config(struct mtk_ddp_comp *comp, unsigned int width,
> > >  	 */
> > >  	threshold = width * height * vrefresh * 4 * 7 / 1000000;
> > >  	reg = RDMA_FIFO_UNDERFLOW_EN |
> > > -	      RDMA_FIFO_PSEUDO_SIZE(RDMA_FIFO_SIZE(rdma)) |
> > > +	      RDMA_FIFO_PSEUDO_SIZE(rdma_fifo_size) |
> > >  	      RDMA_OUTPUT_VALID_FIFO_THRESHOLD(threshold);
> > >  	writel(reg, comp->regs + DISP_REG_RDMA_FIFO_CON);
> > >  }
> > > @@ -284,6 +291,18 @@ static int mtk_disp_rdma_probe(struct platform_device *pdev)
> > >  		return comp_id;
> > >  	}
> > >  
> > > +	if (of_find_property(dev->of_node, "mediatek,rdma_fifo_size", &ret)) {
> > 
> > "mediatek,rdma_fifo_size" does not exists in binding document.
> > 
> > > +		ret = of_property_read_u32(dev->of_node,
> > > +					   "mediatek,rdma_fifo_size",
> > > +					   &priv->fifo_size);
> > > +		if (ret) {
> > > +			dev_err(dev, "Failed to get rdma fifo size\n");
> > > +			return ret;
> > > +		}
> > > +
> > > +		priv->fifo_size *= SZ_1K;
> > 
> > Why not define fifo_size in 'bytes' ?
> > 
> > Regards,
> > CK
> 
> this is align the definition of fifo_size in mtk_disp_rdma_data, it is
> SZ_1K, 
> and the macro RDMA_FIFO_PSEUDO_SIZE calculated with SZ_1K

I mean why not set the fifo size in bytes in device tree. So you need
not to do '*= SZ_1K' here. I think unit of fifo size in kernel is byte.

Regards,
CK

> > 
> > > +	}
> > > +
> > >  	ret = mtk_ddp_comp_init(dev, dev->of_node, &priv->ddp_comp, comp_id,
> > >  				&mtk_disp_rdma_funcs);
> > >  	if (ret) {
> > 
> > 
> 
>