From mboxrd@z Thu Jan 1 00:00:00 1970 From: vladimir_zapolskiy@mentor.com (Vladimir Zapolskiy) Date: Mon, 21 Sep 2015 17:00:33 +0300 Subject: [PATCH v3 2/2] drm: bridge/dw_hdmi: add dw hdmi i2c bus adapter support In-Reply-To: <20150916221819.GJ21084@n2100.arm.linux.org.uk> References: <1440970470-7155-1-git-send-email-vladimir_zapolskiy@mentor.com> <55F9D7F0.4070402@mentor.com> <20150916221819.GJ21084@n2100.arm.linux.org.uk> Message-ID: <56000D81.9080509@mentor.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 17.09.2015 01:18, Russell King - ARM Linux wrote: > On Wed, Sep 16, 2015 at 02:56:57PM -0700, Doug Anderson wrote: >> Yes, I'd expect 100kHz and 400kHz. >> >> I agree that 50ms is non-trivial, but it's also not something you're >> doing lots of. I'd expect that the EDID is read over this channel at >> cable plugin time and then not used much after that. Adding an extra >> 40ms (10ms vs 50ms) before we can access the TV doesn't seem terrible >> for compatibility. >> >> Doing a quick scan for what others in mainline do: >> >> A few can be found with: >> >> $ git grep -A3 hdmiddc | grep clock-freq >> arch/arm/boot/dts/stihxxx-b2120.dtsi- >> clock-frequency = <100000>; >> arch/arm/boot/dts/tegra30-apalis.dtsi- clock-frequency = <100000>; >> arch/arm/boot/dts/tegra30-beaver.dts- clock-frequency = <100000>; >> arch/arm/boot/dts/tegra30-colibri.dtsi- clock-frequency = <100000>; > > This is a sure way to propagate a bug. > > I said in a previous email that you need to check the HDMI and CEA > specs. I've done this, and HDMI 1.3a specifies a maximum SCL clock > rate of 100kHz. > > So that's settled then. 100kHz is must be. Using 400kHz is out of > specification. > FYI I've managed to measure SCL on iMX6, fast mode stands for 333KHz and standard mode stands for 100KHz, therefore I'll set the latter mode. -- With best wishes, Vladimir