Can you try the attached patch w/o without the defaults for i2s_1/2? Not even compile tested...
[added a couple of underscores]
I get this early during boot/probe [ 1.506291] pcm512x 0-004c: pcm512x_set_fmt: failed to read I2S_1: -16 [ 1.512905] pcm512x 0-004c: pcm512x_set_fmt: failed to read PLL_EN: -16 [ 1.519517] pcm512x 0-004c: Failed to set data format: -16 [ 1.525045] pcm512x 0-004c: Failed to set data offset: -16
and then this later, triggered from userspace when an app opens the device [ 14.620344] pcm512x 0-004c: pcm512x_hw_params: I2S_1: 0x2
So, reading *can* work.
I added some traces and verified that accesses to I2S_1/2 fail (as do PLL_EN accesses) when the chip is in Powerdown mode (pcm512x_suspend has set the RQPD bit in the POWER register), which it is when pcm512x_set_fmt runs. During pcm512x_hw_params the chip is in Standby mode instead (pcm512x_resume has cleared the RQPD bit, but the RQST bit is set).
So, my patch seems wrong, and the I2S_1/2 accesses instead need to move to some point where the chip is not in Powerdown mode.
Or, is the problem that pcm512x_set_fmt is called while the codec is suspended and the chip thus is in Powerdown mode? Because, that seems problematic to me?
Cheers, Peter