On Mon, Jun 7, 2021 at 4:56 AM Krzysztof Hałasa <khalasa@xxxxxxx> wrote: > > Hi Hans, > > Hans Verkuil <hverkuil@xxxxxxxxx> writes: > > >> Without this patch, the TDA19971 chip's EDID is inactive. > > > > Was this wrong from the very beginning? How can this ever have been tested > > without an EDID? > > It seems so. I suspect it might have worked in tests because this > register isn't cleared on reboot. I.e., setting it once after power up > makes it work to the next power up. > Or, maybe, the HDMI signal source didn't need EDID. > Krzysztof, Most likely it was that the HDMI signal source I tested with didn't need EDID. I primarily used a V-SG4K HMDI signal generator in my testing and development of the driver (http://www.marshall-usa.com/monitors/model/V-SG4K-HDI.php) which definitely doesn't need it. Other devices I tested with were another Gateworks board with HDMI out (which also didn't need EDID) and occasionally a 1st gen Google Chromecast and Amazon Fire stick (which I'm not sure about). > 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 what the "non-internal" EDID could be - a separate I2C EEPROM > chip? I'm using this on Gateworks' GW54xx boards and I can't see any > such EEPROM in the vicinity of the TDA19971, but I don't know how it is > wired - perhaps Tim has some idea? Not sure where the source above is from (this was all so long ago) but 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. Tim
