Re: [PATCH] drm: bridge: dw-hdmi: Avoid resetting force in the detect function - Russell King

From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Sam Ravnborg <sam@ravnborg.org>
Cc: Fabio Estevam <fabio.estevam@freescale.com>,
	Jernej Skrabec <jernej.skrabec@siol.net>,
	Jonathan Liu <net147@gmail.com>, Jonas Karlman <jonas@kwiboo.se>,
	David Airlie <airlied@linux.ie>,
	Neil Armstrong <narmstrong@baylibre.com>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	Andrzej Hajda <a.hajda@samsung.com>,
	linux-rockchip@lists.infradead.org,
	Boris Brezillon <boris.brezillon@collabora.com>,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
	Liu Ying <victor.liu@nxp.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] drm: bridge: dw-hdmi: Avoid resetting force in the detect function
Date: Sun, 8 Nov 2020 09:57:25 +0000	[thread overview]
Message-ID: <20201108095724.GW1551@shell.armlinux.org.uk> (raw)
In-Reply-To: <20201108095322.GA1129714@ravnborg.org>

On Sun, Nov 08, 2020 at 10:53:22AM +0100, Sam Ravnborg wrote:
> Russell,
> 
> On Sat, Oct 31, 2020 at 07:17:47PM +1100, Jonathan Liu wrote:
> > It has been observed that resetting force in the detect function can
> > result in the PHY being powered down in response to hot-plug detect
> > being asserted, even when the HDMI connector is forced on.
> > 
> > Enabling debug messages and adding a call to dump_stack() in
> > dw_hdmi_phy_power_off() shows the following in dmesg:
> > [  160.637413] dwhdmi-rockchip ff940000.hdmi: EVENT=plugin
> > [  160.637433] dwhdmi-rockchip ff940000.hdmi: PHY powered down in 0 iterations
> > 
> > Call trace:
> > dw_hdmi_phy_power_off
> > dw_hdmi_phy_disable
> > dw_hdmi_update_power
> > dw_hdmi_detect
> > dw_hdmi_connector_detect
> > drm_helper_probe_detect_ctx
> > drm_helper_hpd_irq_event
> > dw_hdmi_irq
> > irq_thread_fn
> > irq_thread
> > kthread
> > ret_from_fork
> > 
> > Fixes: 381f05a7a842 ("drm: bridge/dw_hdmi: add connector mode forcing")
> > Signed-off-by: Jonathan Liu <net147@gmail.com>
> 
> you are the original author of this code - any comments on this patch?

No further comments beyond what has already been discussed, and the
long and short of it is it's been so long that I don't remember why
that code was there. Given that, I'm not even in a position to ack
the change. Sorry.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

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