From: vladimir_zapolskiy@mentor.com (Vladimir Zapolskiy)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v3 2/2] drm: bridge/dw_hdmi: add dw hdmi i2c bus adapter support
Date: Mon, 21 Sep 2015 17:00:33 +0300 [thread overview]
Message-ID: <56000D81.9080509@mentor.com> (raw)
In-Reply-To: <20150916221819.GJ21084@n2100.arm.linux.org.uk>
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
prev parent reply other threads:[~2015-09-21 14:00 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-30 21:34 [PATCH v3 2/2] drm: bridge/dw_hdmi: add dw hdmi i2c bus adapter support Vladimir Zapolskiy
2015-08-31 9:22 ` Philipp Zabel
2015-09-02 22:07 ` Doug Anderson
2015-09-02 22:50 ` Russell King - ARM Linux
2015-09-02 23:00 ` Doug Anderson
2015-09-02 23:04 ` Russell King - ARM Linux
2015-09-02 23:19 ` Doug Anderson
2015-09-16 21:16 ` Vladimir Zapolskiy
2015-09-16 22:02 ` Doug Anderson
2015-09-02 23:43 ` Doug Anderson
2015-09-03 9:19 ` Russell King - ARM Linux
2015-09-03 9:39 ` Thierry Reding
2015-09-03 16:08 ` Doug Anderson
2015-09-08 22:08 ` Wolfram Sang
2015-09-16 20:04 ` Doug Anderson
2015-09-16 20:58 ` Vladimir Zapolskiy
2015-09-16 21:56 ` Doug Anderson
2015-09-16 22:18 ` Russell King - ARM Linux
2015-09-21 14:00 ` Vladimir Zapolskiy [this message]
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