From: Tony Lindgren <tony@atomide.com>
To: Hans Verkuil <hverkuil@xs4all.nl>
Cc: dri-devel@lists.freedesktop.org, Jyri Sarha <jsarha@ti.com>,
Tomi Valkeinen <tomi.valkeinen@ti.com>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
linux-omap@vger.kernel.org, linux-media@vger.kernel.org
Subject: Re: CEC blocks idle on omap4
Date: Mon, 25 Mar 2019 09:18:14 -0700 [thread overview]
Message-ID: <20190325161814.GL19425@atomide.com> (raw)
In-Reply-To: <dc7e900c-52e2-3268-6c08-6a5b0049135a@xs4all.nl>
* Hans Verkuil <hverkuil@xs4all.nl> [190325 15:52]:
> Hi Tony,
>
> On 3/25/19 4:32 PM, Tony Lindgren wrote:
> > Hi Hans,
> >
> > Looks like CONFIG_OMAP4_DSS_HDMI_CEC=y blocks SoC core retention
> > idle on omap4 if selected.
> >
> > Should we maybe move hdmi4_cec_init() to hdmi_display_enable()
> > and hdmi4_cec_uninit() to hdmi_display_disable()?
> >
> > Or add some enable/disable calls in addtion to the init and
> > uninit calls that can be called from hdmi_display_enable()
> > and hdmi_display_disable()?
>
> For proper HDMI CEC behavior the CEC adapter has to remain active
> even if the HPD of the display is low. Some displays pull down the
> HPD when in standby, but CEC can still be used to wake them up.
OK
> And we see this more often as regulations for the maximum power
> consumption of displays are getting more and more strict.
>
> So disabling CEC when the display is disabled is not an option.
OK
> Disabling CEC if the source is no longer transmitting isn't a good
> idea either since the display will typically still send periodic
> CEC commands to the source that it expects to reply to.
Hmm I wonder if we could test for HPD floating and then disable
cec? Then we would know nothing is connected, right?
> The reality is that HDMI CEC and HDMI video are really independent of
> one another. So I wonder if it isn't better to explain the downsides
> of enabling CEC for the omap4 in the CONFIG_OMAP4_DSS_HDMI_CEC
> description. And perhaps disable it by default?
From distro kernel point of view we should find some way to
disable cec dynamically. Can we maybe do something via /sys or
some command line option for cec.ko?
Then if we find a way to check for floating HPD pin or something
we could support that too.
Regards,
Tony
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WARNING: multiple messages have this Message-ID (diff)
From: Tony Lindgren <tony@atomide.com>
To: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-omap@vger.kernel.org, Jyri Sarha <jsarha@ti.com>
Subject: Re: CEC blocks idle on omap4
Date: Mon, 25 Mar 2019 09:18:14 -0700 [thread overview]
Message-ID: <20190325161814.GL19425@atomide.com> (raw)
In-Reply-To: <dc7e900c-52e2-3268-6c08-6a5b0049135a@xs4all.nl>
* Hans Verkuil <hverkuil@xs4all.nl> [190325 15:52]:
> Hi Tony,
>
> On 3/25/19 4:32 PM, Tony Lindgren wrote:
> > Hi Hans,
> >
> > Looks like CONFIG_OMAP4_DSS_HDMI_CEC=y blocks SoC core retention
> > idle on omap4 if selected.
> >
> > Should we maybe move hdmi4_cec_init() to hdmi_display_enable()
> > and hdmi4_cec_uninit() to hdmi_display_disable()?
> >
> > Or add some enable/disable calls in addtion to the init and
> > uninit calls that can be called from hdmi_display_enable()
> > and hdmi_display_disable()?
>
> For proper HDMI CEC behavior the CEC adapter has to remain active
> even if the HPD of the display is low. Some displays pull down the
> HPD when in standby, but CEC can still be used to wake them up.
OK
> And we see this more often as regulations for the maximum power
> consumption of displays are getting more and more strict.
>
> So disabling CEC when the display is disabled is not an option.
OK
> Disabling CEC if the source is no longer transmitting isn't a good
> idea either since the display will typically still send periodic
> CEC commands to the source that it expects to reply to.
Hmm I wonder if we could test for HPD floating and then disable
cec? Then we would know nothing is connected, right?
> The reality is that HDMI CEC and HDMI video are really independent of
> one another. So I wonder if it isn't better to explain the downsides
> of enabling CEC for the omap4 in the CONFIG_OMAP4_DSS_HDMI_CEC
> description. And perhaps disable it by default?
From distro kernel point of view we should find some way to
disable cec dynamically. Can we maybe do something via /sys or
some command line option for cec.ko?
Then if we find a way to check for floating HPD pin or something
we could support that too.
Regards,
Tony
next prev parent reply other threads:[~2019-03-25 16:18 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-25 15:32 CEC blocks idle on omap4 Tony Lindgren
2019-03-25 15:32 ` Tony Lindgren
2019-03-25 15:51 ` Hans Verkuil
2019-03-25 15:51 ` Hans Verkuil
2019-03-25 15:55 ` Laurent Pinchart
2019-03-25 15:55 ` Laurent Pinchart
2019-03-25 16:12 ` Hans Verkuil
2019-03-25 16:12 ` Hans Verkuil
2019-03-25 16:21 ` Tony Lindgren
2019-03-25 16:21 ` Tony Lindgren
2019-03-25 16:27 ` Hans Verkuil
2019-03-25 16:27 ` Hans Verkuil
2019-03-25 16:33 ` Tony Lindgren
2019-03-25 16:33 ` Tony Lindgren
2019-03-25 16:18 ` Tony Lindgren [this message]
2019-03-25 16:18 ` Tony Lindgren
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