On Wed, Aug 29, 2018 at 02:20:19PM +0000, Joakim Tjernlund wrote: > I see when I boot: > [ 0.602608] i2c /dev entries driver > [ 0.608010] mpc-i2c e0003000.i2c: timeout 1000000 us > [ 0.623056] rtc-ds1307 1-0068: read: 17 33 13 04 29 08 18 > [ 0.623096] rtc-ds1307 1-0068: read secs=17, mins=33, hours=13, mday=29, mon=7, year=118, wday=3 > [ 0.623554] rtc-ds1307 1-0068: char device (253:0) > [ 0.623609] rtc-ds1307 1-0068: registered as rtc0 > [ 0.629544] i2c i2c-0: Added multiplexed i2c bus 1 > [ 0.635788] i2c i2c-0: Added multiplexed i2c bus 2 > [ 0.642584] i2c i2c-0: Added multiplexed i2c bus 3 > [ 0.649617] i2c i2c-0: Added multiplexed i2c bus 4 > [ 0.657617] i2c i2c-0: Added multiplexed i2c bus 5 > [ 0.666545] i2c i2c-0: Added multiplexed i2c bus 6 > [ 0.673730] i2c i2c-0: Added multiplexed i2c bus 7 > [ 0.679968] i2c i2c-0: Added multiplexed i2c bus 8 > [ 0.686263] i2c i2c-0: Added multiplexed i2c bus 9 > [ 0.692515] i2c i2c-0: Added multiplexed i2c bus 10 > [ 0.698832] i2c i2c-0: Added multiplexed i2c bus 11 > [ 0.705256] i2c i2c-0: Added multiplexed i2c bus 12 > [ 0.711551] i2c i2c-0: Added multiplexed i2c bus 13 > [ 0.717979] i2c i2c-0: Added multiplexed i2c bus 14 > [ 0.724342] i2c i2c-0: Added multiplexed i2c bus 15 > [ 0.730654] i2c i2c-0: Added multiplexed i2c bus 16 > [ 0.735635] i2c-mux-gpio e0000000.soc8321:i2cmux: 16 port mux on MPC adapter at 0xe0003000 adapter > > This looks like the I2C based RTC is accessed before i2c-mux-gpio is active? I once got confused by this, too. As part of the initialization of the mux, all devices behind it are probed. During that probe, transactions happen. Once all devices are probed, then the mux initialization is finished, and *then* the "added bus" message is printed. Couldn't think of a better way back then, because we don't want to print this message before everything with regard to the mux initialization was successful. At least, this is how I recall all of this.
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