Hello,
On 2/26/24 16:01, Andy Shevchenko wrote:
On Mon, Feb 26, 2024 at 03:46:56PM +0200, Arturas Moskvinas wrote:
Move output enabling after chip registers are cleared.
Does this fix anything? If so, maybe elaborate a bit the potential behavioural
changes on the real lines.
Chip outputs are enabled[1] before actual reset is performed[2] which
might cause pin output value to flip flop if previous pin value was set
to 1 in chip. Change fixes that behavior by making sure chip is fully
reset before all outputs are enabled.
Flip-flop can be noticed when module is removed and inserted again and
one of the pins was changed to 1 before removal. 100 microsecond
flipping is noticeable on oscilloscope (100khz SPI bus).
For a properly reset chip - output is enabled around 100 microseconds
(on 100khz SPI bus) later during probing process hence should be
irrelevant behavioral change.
[1] -
https://elixir.bootlin.com/linux/v6.7.4/source/drivers/gpio/gpio-74x164.c#L130
[2] -
https://elixir.bootlin.com/linux/v6.7.4/source/drivers/gpio/gpio-74x164.c#L150
Arturas Moskvinas
