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

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Message-ID: <20201108095724.GW1551@shell.armlinux.org.uk>
Date:   Sun, 8 Nov 2020 09:57:25 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Sam Ravnborg <sam@...nborg.org>
Cc:     Jonathan Liu <net147@...il.com>,
        linux-rockchip@...ts.infradead.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Fabio Estevam <fabio.estevam@...escale.com>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Jonas Karlman <jonas@...boo.se>,
        David Airlie <airlied@...ux.ie>,
        Neil Armstrong <narmstrong@...libre.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Liu Ying <victor.liu@....com>
Subject: Re: [PATCH] drm: bridge: dw-hdmi: Avoid resetting force in the
 detect function

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@...il.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/
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