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([2a01:e0a:90c:e290:b4:316d:263e:1360]) by smtp.gmail.com with ESMTPSA id h10sm13764777wrt.40.2021.04.20.08.19.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 20 Apr 2021 08:19:53 -0700 (PDT) Subject: Re: [PATCH 0/2] drm/bridge: dw-hdmi: disable loading of DW-HDMI CEC sub-driver To: Hans Verkuil , Laurent Pinchart Cc: 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 References: <20210416092737.1971876-1-narmstrong@baylibre.com> <96b9e144-0791-4c19-3e3c-b0e9efb86138@baylibre.com> From: Neil Armstrong Organization: Baylibre Message-ID: <0821533b-9e6a-237e-3845-741e82de4ed9@baylibre.com> Date: Tue, 20 Apr 2021 17:19:52 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210420_081955_711771_36DA9EBB X-CRM114-Status: GOOD ( 27.43 ) X-BeenThere: linux-amlogic@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-amlogic" Errors-To: linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org 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. > > 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 Neil > > Regards, > > Hans > >> >> Neil >> >>> >>>> 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(-) >>>> >>> >> >> _______________________________________________ >> dri-devel mailing list >> dri-devel@lists.freedesktop.org >> https://lists.freedesktop.org/mailman/listinfo/dri-devel >> > _______________________________________________ linux-amlogic mailing list linux-amlogic@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-amlogic