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From: Yegor Yefremov <yegorslists-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org>
To: Shubhrajyoti Datta
	<omaplinuxkernel-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>,
	Linux I2C <linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	shubhrajyoti-l0cyMroinI0@public.gmane.org
Subject: Re: OMAP: send i2c message ignoring NAK
Date: Wed, 11 Jul 2012 18:23:41 +0200	[thread overview]
Message-ID: <CAGm1_kvLwj3iFz5M6zc+pitS_45OYPYw=aBU4bv8TdOhH600NA@mail.gmail.com> (raw)
In-Reply-To: <CAM=Q2cv2yCEaxjSL45PSpf8k8pgMuhr88TJ-RWc0OW1GL+n6Dg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On Tue, Jul 10, 2012 at 5:08 PM, Shubhrajyoti Datta
<omaplinuxkernel-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> On Tue, Jul 10, 2012 at 8:29 PM, Yegor Yefremov
> <yegorslists-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote:
>> On Tue, Jul 3, 2012 at 10:32 AM, Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org> wrote:
>>> On Tue, 3 Jul 2012 10:12:09 +0200, Yegor Yefremov wrote:
>>>> I'm using the second i2c channel to connect to HDMI transmitter
>>>> sii9022a. In order to get EDID information from the attached monitor
>>>> the sii9022a chip passes i2c request direct to the monitors i2c bus.
>>>> To return to sii9022a mode one has to write data to HDMI transmitter,
>>>> but this data won't be acknowledged. Because of this i2c produces
>>>> timeout permanently (omap_i2c omap_i2c.2: controller timed out), so no
>>>> communication is possible. The last bits I see on the scope are the
>>>> i2c address of sii9022a. The CPU automatically end the transfer.
>>>>
>>>> The HDMI chip has i2c address 0x72 (8-bit notation) and EDID channel
>>>> 0xa0 (8-bit notation). AFAIK there is only one device at a time on the
>>>> bus, i.e. as soon as I switch sii9022a to access monitor only 0xa0
>>>> responds to the queries. And I need to send a message to 0x72 ignoring
>>>> normal i2c conditions in order to turn it back in normal mode.
>>>>
>>>> The driver for this HDMI transmitter can be found here:
>>>> http://gitorious.org/efikamx/linux-kernel.git
>>>> (drivers/video/mxc/siihdmi.c)
>>>>
>>>> How can I send this write request without awaiting for ACK?
>>>
>>> Use I2C_M_IGNORE_NAK, see Documentation/i2c/i2c-protocol.
>>
>> Jean, thanks for the tip. I got it working by disabling the omap-i2c
>> driver and enabling i2c-gpio on the same pins. Only in this
>> combination and I2C_M_IGNORE_NAK I could get back to the HDMI chip.
>> OMAP i2c driver/I2C_M_IGNORE_NAK combo is not working. But I still got
>> no chance to try the latest kernel.
>
> OK may be you are missing patches like
> http://git.kernel.org/?p=linux/kernel/git/tmlind/linux-omap.git;a=commit;h=464fca36d98b97ccd05e4f200ab7483d3acc8345

No, i don't.

> Personally will recommend the latest kernel.

To do that, I'll have to use device tree (there is no board file) and
I have no experience with this so far. So I'll have to postpone this
till am335x support stabilizes.

Yegor

  parent reply	other threads:[~2012-07-11 16:23 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-07-03  8:12 OMAP: send i2c message ignoring NAK Yegor Yefremov
     [not found] ` <CAGm1_ktL96X7kF3tvKErtirwnL7FGU=zGe+EyhX4GcUkZUeSkQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-07-03  8:32   ` Jean Delvare
     [not found]     ` <20120703103221.62fcb7ae-R0o5gVi9kd7kN2dkZ6Wm7A@public.gmane.org>
2012-07-10 14:59       ` Yegor Yefremov
     [not found]         ` <CAGm1_kvBerv_Ot-NX2+ozZT3y+h4ECzwb-MM0-v=3M9aRRznzA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-07-10 15:08           ` Shubhrajyoti Datta
     [not found]             ` <CAM=Q2cv2yCEaxjSL45PSpf8k8pgMuhr88TJ-RWc0OW1GL+n6Dg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-07-11 16:23               ` Yegor Yefremov [this message]
     [not found]                 ` <CAGm1_kvLwj3iFz5M6zc+pitS_45OYPYw=aBU4bv8TdOhH600NA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-07-11 16:52                   ` Shubhrajyoti
     [not found]                     ` <4FFDAF5A.8070205-l0cyMroinI0@public.gmane.org>
2012-07-12  5:24                       ` Datta, Shubhrajyoti
     [not found]                         ` <CANQgH-YxYY7M6o4Hxw0kq9=GSwF8TSgiobXLJoPnGhj=c3w4KQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-07-17  9:31                           ` Yegor Yefremov
     [not found]                             ` <CAGm1_ktYqq5HKt13RuQVL8axX0FUnZ_5a6va7BRuUschQRKERQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-07-17 14:01                               ` Shubhrajyoti Datta
     [not found]                                 ` <CAM=Q2ct_mfGiuKrX9KAuk7B+PA==FRL7DPOfge9fRAuFg6bA3Q-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-07-19 13:05                                   ` Yegor Yefremov
     [not found]                                     ` <CAGm1_ktVXmEBZz90_SMB+WmZGax5DwoXD5pr66Dja=8QW1QcGA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-07-19 13:26                                       ` Shubhrajyoti
2012-07-11 16:52                   ` Shubhrajyoti

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