Re: [PATCH] TDA1997x: enable EDID support

Krzysztof Hałasa
2021-06-08T04:55:42Z

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.