TDA1997x: enable EDID support

Without this patch, the TDA19971 chip's EDID is inactive.

Signed-off-by: Krzysztof Halasa <khalasa@piap.pl>

Tim,

Tim Harvey <tharvey@gateworks.com> writes:

>> I'm looking at the previous version of this driver from Gateworks and it
>> contains:
>>
>>      /* Configure EDID
>>       *
>>       * EDID_ENABLE bits:
>>       *  7 - nack_off
>>       *  6 - edid_only
>>       *  1 - edid_b_en
>>       *  0 - edid_a_en
>>       */
>>      reg = io_read(REG_EDID_ENABLE);
>>      if (!tda1997x->internal_edid)
>>          reg &= ~0x83; /* EDID Nack ON */
>>      else
>>          reg |= 0x83;  /* EDID Nack OFF */
>>      io_write(REG_EDID_ENABLE, reg);

> Not sure where the source above is from (this was all so long ago) but

That's your gateworks_fslc_3.14_1.0.x_ga branch (3.14 is the kernel and
1.0.x_ga is IIRC some Freescale versioning) :-)

> my guess is that 'internal_edid' meant an EDID had been provided via
> software and the else case meant there was no EDID available.
> There is no support on that chip for an external EEPROM.

Right. I guess the else meant it was available and &= ~83 meant no
EDID... Anyway one could simply drop a 24c02 or a similar chip directly
to SDA/SCL HDMI lines, that's what the monitor makers had been doing for
a long time. Then, I guess, you would need the internal_edid = 0
(otherwise the TDA chip would be fighting the EEPROM on the SDA line).
Not that I know of any such design using this driver, I guess we can
safely skip this part.

Hi Krzysztof,

On 08/06/2021 06:54, Krzysztof Hałasa wrote:
> Tim,
> 
> Tim Harvey <tharvey@gateworks.com> writes:
> 
>>> I'm looking at the previous version of this driver from Gateworks and it
>>> contains:
>>>
>>>      /* Configure EDID
>>>       *
>>>       * EDID_ENABLE bits:
>>>       *  7 - nack_off
>>>       *  6 - edid_only
>>>       *  1 - edid_b_en
>>>       *  0 - edid_a_en
>>>       */
>>>      reg = io_read(REG_EDID_ENABLE);
>>>      if (!tda1997x->internal_edid)
>>>          reg &= ~0x83; /* EDID Nack ON */
>>>      else
>>>          reg |= 0x83;  /* EDID Nack OFF */
>>>      io_write(REG_EDID_ENABLE, reg);
> 
>> Not sure where the source above is from (this was all so long ago) but
> 
> That's your gateworks_fslc_3.14_1.0.x_ga branch (3.14 is the kernel and
> 1.0.x_ga is IIRC some Freescale versioning) :-)
> 
>> my guess is that 'internal_edid' meant an EDID had been provided via
>> software and the else case meant there was no EDID available.
>> There is no support on that chip for an external EEPROM.
> 
> Right. I guess the else meant it was available and &= ~83 meant no
> EDID... Anyway one could simply drop a 24c02 or a similar chip directly
> to SDA/SCL HDMI lines, that's what the monitor makers had been doing for
> a long time. Then, I guess, you would need the internal_edid = 0
> (otherwise the TDA chip would be fighting the EEPROM on the SDA line).
> Not that I know of any such design using this driver, I guess we can
> safely skip this part.
> 

OK, I think the history is clear. Can you post a v2 with a Fixes tag and
comment a bit on why this was not caught before?

Regards,

	Hans

On 08/06/2021 10:45, Krzysztof Hałasa wrote:
> Hans Verkuil <hverkuil@xs4all.nl> writes:
> 
>> OK, I think the history is clear. Can you post a v2 with a Fixes tag and
>> comment a bit on why this was not caught before?
> 
> Sure, will do. That "Fixes" tag... since it's from the beginning (the
> Gateworks' branch was never a part of the official tree), do I still
> need it? It would have to point to the initial submission of this
> driver.
> 

Yes, that's fine. It's been broken since the beginning, so the Fixes
tag will indicate that.

Regards,

	Hans