I'm trying to track yet another vendor vs current OpenWrt driver mishandling.
In my vendor kernel:
[ 2.243263] i2c-mt7621 1e000900.i2c: clock 100KHz, re-start not support
Which is this driver:
* drivers/i2c/busses/i2c-mt7621.c
*
* Copyright (C) 2013 Steven Liu <steven_...@mediatek.com>
* Copyright (C) 2016 Michael Lee <igv...@gmail.com>
*
* Improve driver for i2cdetect from i2c-tools to detect i2c devices on the bus.
* (C) 2014 Sittisak <sittis...@hotmail.com>
This is kernel 4.14.131
Which of course works fine.
In 5.10 and 5.15 current OpenWrt kernels:
[ 2.917685] i2c-mt7621 1e000900.i2c: clock 100 kHz
Writes work correctly. This for example sets LEDs via i2c (handled by the MCU
and its GPIOs - I control this code too):
# i2ctransfer -y 0 w1@0x50 0x43 w3 3 2 1
Wed Feb 15 18:23:01 2023 kern.debug kernel: [ 307.979880] i2c i2c-0: ioctl,
cmd=0x705, arg=0x7fb736f0
Wed Feb 15 18:23:01 2023 kern.debug kernel: [ 307.979927] i2c i2c-0: ioctl,
cmd=0x703, arg=0x50
Wed Feb 15 18:23:01 2023 kern.debug kernel: [ 307.979954] i2c i2c-0: ioctl,
cmd=0x707, arg=0x7fb736f0
# i2ctransfer -y 0 w1@0x50 1 r1
Wed Feb 15 18:23:04 2023 kern.debug kernel: [ 310.921389] i2c i2c-0: ioctl,
cmd=0x705, arg=0x7febfd60
Wed Feb 15 18:23:04 2023 kern.debug kernel: [ 310.921437] i2c i2c-0: ioctl,
cmd=0x703, arg=0x50
Wed Feb 15 18:23:04 2023 kern.debug kernel: [ 310.921463] i2c i2c-0: ioctl,
cmd=0x707, arg=0x7febfd60
0x03
# i2ctransfer -y 0 w1@0x50 1 r1
Wed Feb 15 18:23:06 2023 kern.debug kernel: [ 312.714856] i2c i2c-0: ioctl,
cmd=0x705, arg=0x7feaf3e0
Wed Feb 15 18:23:06 2023 kern.debug kernel: [ 312.714903] i2c i2c-0: ioctl,
cmd=0x703, arg=0x50
Wed Feb 15 18:23:06 2023 kern.debug kernel: [ 312.714928] i2c i2c-0: ioctl,
cmd=0x707, arg=0x7feaf3e0
0x00
In particular, for the first read attempt, the value is always the first
value sent as part of the last write. i.e, 3 in this case. After, that,
it's always 0 (the correct answer ought to be 0xf).
Clues where to look please?
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