linux-kernel - Re: [PATCH v3 8/8] drm/mediatek: add third ddp path

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Date:   Mon, 28 May 2018 10:50:15 +0800
From:   CK Hu <ck.hu@...iatek.com>
To:     Stu Hsieh <stu.hsieh@...iatek.com>
CC:     Philipp Zabel <p.zabel@...gutronix.de>,
        David Airlie <airlied@...ux.ie>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.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>, <srv_heupstream@...iatek.com>
Subject: Re: [PATCH v3 8/8] drm/mediatek: add third ddp path

Hi, Stu:

On Mon, 2018-05-28 at 10:26 +0800, Stu Hsieh wrote:
> Hi, CK:
> I've some idea as below.
> 
> On Fri, 2018-05-25 at 13:00 +0800, CK Hu wrote:
> > Hi, Stu:
> > 
> > On Fri, 2018-05-25 at 10:34 +0800, stu.hsieh@...iatek.com wrote:
> > > From: Stu Hsieh <stu.hsieh@...iatek.com>
> > > 
> > > This patch create third crtc by third ddp path
> > > 
> > 
> > Apply this patch before the patch 'Add support for mediatek SOC MT2712'
> > because this patch is necessary for mt2712.
> > 
> > > Signed-off-by: Stu Hsieh <stu.hsieh@...iatek.com>
> > > ---
> > >  drivers/gpu/drm/mediatek/mtk_drm_drv.c | 5 +++++
> > >  1 file changed, 5 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> > > index b32c4cc8d051..3a866e1d6af4 100644
> > > --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> > > +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> > > @@ -267,6 +267,11 @@ static int mtk_drm_kms_init(struct drm_device *drm)
> > >  	if (ret < 0)
> > >  		goto err_component_unbind;
> > >  
> > > +	ret = mtk_drm_crtc_create(drm, private->data->third_path,
> > > +				  private->data->third_len);
> > 
> > I think you should prevent doing this for mt8173 and mt2701 because that
> > two SoC has only two ddp path.
> 
> Now, 8173 and 2701 have only two ddp path, there is a problem on run
> time. 
> There are three crtc for drm resource, and there is nothing in third
> crtc. 
> Because 8173 and 2701 have no third ddp, and the third ddp_len is zero.
> So, I want to add the condition like following in mtk_crtc_create()
> if (path_len == 0)
> 	return 0;
> 
> Then, the valur ret is zero and it would not create the null third crtc.

This sounds good to me.

Regards,
CK

> 
> 
> Regards,
> Stu
> 
> > 
> > Regards,
> > CK
> > 
> > > +	if (ret < 0)
> > > +		goto err_component_unbind;
> > > +
> > >  	/* Use OVL device for all DMA memory allocations */
> > >  	np = private->comp_node[private->data->main_path[0]] ?:
> > >  	     private->comp_node[private->data->ext_path[0]];
> > 
> > 
> 
>