linux-kernel - Re: [RFC 2/3] drm/mediatek: add support for Mediatek SoC MT2701

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Date:	Fri, 13 May 2016 11:59:16 +0800
From:	CK Hu <ck.hu@...iatek.com>
To:	<yt.shen@...iatek.com>
CC:	<dri-devel@...ts.freedesktop.org>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	"Mark Rutland" <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"Russell King" <linux@....linux.org.uk>,
	David Airlie <airlied@...ux.ie>,
	"Matthias Brugger" <matthias.bgg@...il.com>,
	Mao Huang <littlecvr@...omium.org>,
	"Bibby Hsieh" <bibby.hsieh@...iatek.com>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-mediatek@...ts.infradead.org>,
	<srv_heupstream@...iatek.com>,
	"Sascha Hauer" <kernel@...gutronix.de>
Subject: Re: [RFC 2/3] drm/mediatek: add support for Mediatek SoC MT2701

Hi, YT:

On Thu, 2016-05-12 at 19:49 +0800, yt.shen@...iatek.com wrote:
> From: YT Shen <yt.shen@...iatek.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@...iatek.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