Hi,
Am 03.10.2014 um 09:56 schrieb Vladimir Komendantskiy:
The Allwinner SoCs that have an HDMI pin, also have a memory-mapped
HDMI-CEC register located at HDMI base 0xf1c16000 plus the offset
0x214. This register provides the following bits
#define CEC_RX 0x0100 /* phys. line value, either high or low */
#define CEC_TX 0x0200
#define CEC_ENABLE 0x0800
Other bits are unused.
I asked Allwinner about CEC once but they only replied that A10s
doesn't have a hardware CEC core.
You can find examples of using the CEC register in some unfinished CEC
code in the 3.4 linux-sunxi kernel.
Thx, a lot I found this PATCH
https://groups.google.com/forum/#!msg/linux-sunxi/cNbMiwzgGJ0/tK-KvXkn-pQJ
And the source
https://github.com/linux-sunxi/linux-sunxi/blob/sunxi-3.4/drivers/video/sunxi/hdmi/hdmi_cec.c
I'll take a closer look on this. It looks like they do bitbanging on
those two bits.
regards,
Christian
--Vladimir
On 3 October 2014 07:33, Chen-Yu Tsai <[email protected]
<mailto:[email protected]>> wrote:
Hi,
On Fri, Oct 3, 2014 at 3:29 AM, [email protected]
<mailto:[email protected]> <[email protected]
<mailto:[email protected]>> wrote:
> I
>
> On Thu, Oct 2, 2014 at 1:19 PM, Christian Ege <[email protected]
<mailto:[email protected]>> wrote:
>> During a quick search I had not been able to find any HDMI CEC
driver. In
>> the docs available there is only one Register about CEC.
>>
>> I thought about implementation of an driver and libcec support
for the A20.
>
> I believe CEC is just I2C on the HDMI connector.
>
> So maybe --- it is one of the I2C devices. Then that bit enables it
> onto the HDMI pin? Just a guess.
>
> EDID works the same way. How is it implemented?
You are referring to DDC. The HDMI block has a separate DDC
controller.
IIRC, the DDC pins also have standard TWI muxed on them, so you could
use either one.
But this is entirely irrelevant to the original question.
As Christian stated, the HDMI block does have a register named
HDMI_HDP_CEC. However it does not contain any useful descriptions.
Also the SoC does have a pin for HDMI CEC.
Best ask Allwinner for some help.
ChenYu
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