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Tue, 20 Apr 2021 22:49:58 +0000 Received: from pendragon.ideasonboard.com (62-78-145-57.bb.dnainternet.fi [62.78.145.57]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 5293345E; Wed, 21 Apr 2021 00:49:40 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1618958980; bh=tnPqQylg0M/heoMDy9x5XiXEnGZ70xHfOc6q1pK7LwQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ZeMKknPmyhvE4Lv+KgrktMqxfIhcblSiEh0KPDRygcger3YAT3GSLEBBVqXh7qDG3 LUCWeoNI6c8vlxZEBDR5b4U2e8itmNqfq+KD8TT6Vjcyoxfawp1ukhGUyh4Uuk+uES vWsUrRluJfe99MxGLvGZHiOc3SPvj76DvRnhj3UA= Date: Wed, 21 Apr 2021 01:49:36 +0300 From: Laurent Pinchart To: Neil Armstrong Cc: Hans Verkuil , jernej.skrabec@siol.net, jonas@kwiboo.se, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, robert.foss@linaro.org, linux-amlogic@lists.infradead.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 0/2] drm/bridge: dw-hdmi: disable loading of DW-HDMI CEC sub-driver Message-ID: References: <20210416092737.1971876-1-narmstrong@baylibre.com> <96b9e144-0791-4c19-3e3c-b0e9efb86138@baylibre.com> <0821533b-9e6a-237e-3845-741e82de4ed9@baylibre.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <0821533b-9e6a-237e-3845-741e82de4ed9@baylibre.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210420_154954_618761_AA10B272 X-CRM114-Status: GOOD ( 31.99 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Apr 20, 2021 at 05:19:52PM +0200, Neil Armstrong wrote: > On 20/04/2021 17:13, Hans Verkuil wrote: > > On 16/04/2021 13:38, Neil Armstrong wrote: > >> On 16/04/2021 11:58, Laurent Pinchart wrote: > >>> Hi Neil, > >>> > >>> On Fri, Apr 16, 2021 at 11:27:35AM +0200, Neil Armstrong wrote: > >>>> This adds DW-HDMI driver a glue option to disable loading of the CEC sub-driver. > >>>> > >>>> On some SoCs, the CEC functionality is enabled in the IP config bits, but the > >>>> CEC bus is non-functional like on Amlogic SoCs, where the CEC config bit is set > >>>> but the DW-HDMI CEC signal is not connected to a physical pin, leading to some > >>>> confusion when the DW-HDMI CEC controller can't communicate on the bus. > >>> > >>> If we can't trust the CEC config bit, would it be better to not use it > >>> at all, and instead let each platform glue logic tell whether to enable > >>> CEC or not ? > >> > >> Actually, the CEC config bit is right, the HW exists and should be functional, but > >> this bit doesn't tell if the CEC signal is connected to something. > >> > >> This lies in the IP integration, like other bits under the "amlogic,meson-*-dw-hdmi" > >> umbrella. > >> > >> The first attempt was by Hans using DT, but adding a property in DT for a vendor > >> specific compatible doesn't make sense. Another idea would be to describe the > >> CEC signal endpoint like we do for video signal, but I think this is out of scope and > >> this solution is much simpler and straightforward, and it's more an exception than > >> a general use case to solve. > > > > While a DT property might not make sense in this particular case, I still > > believe that it is a perfectly valid approach in general: whether or not > > the CEC pin is connected is at the hardware level decision, it is not > > something that software can detect. If the designer of the board didn't > > connect it, then the only place you can define that is in the device tree. > > Agreed, we need to define a smart way to declare CEC bus relationship in DT, the side > effect would be to handle this particular case. I wonder if it would make sense to use the OF graph bindings to describe the connection between the CEC controller and the CEC "device" (which I assume in most cases will be a DT node for a physical connector). Or is this overkill ? > > Anyway, for meson I am fine with this solution. At least it prevents creating > > a non-functioning cec device. So for this series: > > > > Acked-by: Hans Verkuil > > Thanks, > > Applying this serie to drm-misc-next > > >>>> Jernej Skrabec (1): > >>>> drm/bridge/synopsys: dw-hdmi: Add an option to suppress loading CEC > >>>> driver > >>>> > >>>> Neil Armstrong (1): > >>>> drm/meson: dw-hdmi: disable DW-HDMI CEC sub-driver > >>>> > >>>> drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 2 +- > >>>> drivers/gpu/drm/meson/meson_dw_hdmi.c | 1 + > >>>> include/drm/bridge/dw_hdmi.h | 2 ++ > >>>> 3 files changed, 4 insertions(+), 1 deletion(-) -- Regards, Laurent Pinchart _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel