I´m also trying to get the MAX98357A running on a Linkit Smart 7688 with LEDE master branch (kernel 4.9). The previous manuals about configuring and patching helped me a lot - thanks for it.
Now I´m able to play a mp3-file with madplay and can hear the sound, but there is one issue.
After stopping the sound the loudspeaker gets hot, because of ~5V DC output.
In the MAX datasheet is written "do not remove LRCLK while BCLK is present -> may cause a high DC output". This seems to be the case. In I2S mode the datasheet tells BLCK = "rising edge".
Am I wrong or is it needed to invert the BCLK signal for the MAX98357A in the simple-sound-card settings to get a I2S mode running properly?
I tried to set bitclock-inversion in the simple card setup, but it returned with a ralink-i2s / ASoC issue "Failed to set DAI format -22".
Unfortunately, currently no oscilloscope available to measure it...
Thanks in advance for any hints from you...