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Message-ID: <1463398781.13038.4.camel@mtksdaap41>
Subject: Re: [RFC 2/3] drm/mediatek: add support for Mediatek SoC MT2701
From: YT Shen <yt.shen@mediatek.com>
To: CK Hu <ck.hu@mediatek.com>
CC: <dri-devel@lists.freedesktop.org>, Philipp Zabel <p.zabel@pengutronix.de>,
        Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>,
        "Mark Rutland" <mark.rutland@arm.com>,
        Ian Campbell <ijc+devicetree@hellion.org.uk>,
        Kumar Gala <galak@codeaurora.org>,
        "Russell King" <linux@arm.linux.org.uk>,
        David Airlie <airlied@linux.ie>,
        "Matthias Brugger" <matthias.bgg@gmail.com>,
        Mao Huang <littlecvr@chromium.org>,
        "Bibby Hsieh" <bibby.hsieh@mediatek.com>, <devicetree@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <linux-arm-kernel@lists.infradead.org>,
        <linux-mediatek@lists.infradead.org>, <srv_heupstream@mediatek.com>,
        "Sascha Hauer" <kernel@pengutronix.de>
Date: Mon, 16 May 2016 19:39:41 +0800
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Hi CK,
On Fri, 2016-05-13 at 11:59 +0800, CK Hu wrote:
> Hi, YT:
> 
> On Thu, 2016-05-12 at 19:49 +0800, yt.shen@mediatek.com wrote:
> > From: YT Shen <yt.shen@mediatek.com>
> > 
> > This patch add support for the Mediatek MT2701 DISP subsystem.
> > There is only one OVL engine in MT2701, and we have shadow
> > register support here.
> > 
> > Signed-off-by: YT Shen <yt.shen@mediatek.com>
> > ---
> 
> > @@ -385,12 +422,16 @@ static void mtk_drm_crtc_atomic_begin(struct drm_crtc *crtc,
> >  		mtk_crtc->event = state->base.event;
> >  		state->base.event = NULL;
> >  	}
> > +
> > +	if (priv->data->shadow_register)
> > +		mtk_disp_mutex_acquire(mtk_crtc->mutex);
> >  }
> >  
> > @@ -409,6 +450,11 @@ static void mtk_drm_crtc_atomic_flush(struct drm_crtc *crtc,
> >  	}
> >  	if (pending_planes)
> >  		mtk_crtc->pending_planes = true;
> > +
> > +	if (priv->data->shadow_register) {
> > +		mtk_crtc_ddp_config(crtc);
> > +		mtk_disp_mutex_release(mtk_crtc->mutex);
> > +	}
> >  }
> >  
> 
> I think it's better to call mtk_disp_mutex_acquire() and
> mtk_disp_mutex_release() as near as possible to prevent mutex locked for
> a long time. All HW register access of this atomic setting is in
> mtk_crtc_ddp_config(), so it's better to move mtk_disp_mutex_acquire()
> just before mtk_crtc_ddp_config().
> 
> Regards,
> CK
I'll do this in the next version.  Thanks for the review.

Regards,
yt.shen