linux-kernel - Re: [PATCH] drm/bridge: dw-hdmi: fix hdmi display lost

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Message-ID: <20160811083220.GS1041@n2100.armlinux.org.uk>
Date:	Thu, 11 Aug 2016 09:32:20 +0100
From:	Russell King - ARM Linux <linux@...linux.org.uk>
To:	Mark Yao <mark.yao@...k-chips.com>
Cc:	David Airlie <airlied@...ux.ie>, Heiko Stuebner <heiko@...ech.de>,
	dri-devel@...ts.freedesktop.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Fabio Estevam <fabio.estevam@...escale.com>,
	Liu Ying <gnuiyl@...il.com>
Subject: Re: [PATCH] drm/bridge: dw-hdmi: fix hdmi display lost

On Thu, Aug 11, 2016 at 03:54:03PM +0800, Mark Yao wrote:
> hdmi->disabled maybe not match to the real hardware status.
> 
> ->dw_hdmi_bridge_enable()
>   hdmi->disabled = false;
> -->dw_hdmi_update_power()
>    if (hdmi->rxsense)
>        force = DRM_FORCE_ON;
>    else
>        force = DRM_FORCE_OFF;
> 
> hdmi->rxsense maybe false on bridge enable path, then hdmi->disabled
> is false, but actually hardware is power off, they are not match.

... which is correct.  If rxsense is false, it means there is nothing
plugged in, so we don't power the hardware up until something _is_
plugged in.

When something is plugged in, we get the HPD and RXSENSE events, which
will cause dw_hdmi_update_power() to be called.

hdmi->disabled is merely a bit mask of things that would cause us to
want to avoid powering the hardware up when rxsense becomes true.

-- 
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