On 23.05.2017 11:18, Nikita Yushchenko wrote:
Reset GPIO is active low.
Currently driver uses gpiod_set_value(1) to clean reset, which depends
on device tree to contain GPIO_ACTIVE_HIGH - that does not match reality.
This fixes driver to use _raw version of gpiod_set_value() to enforce
active-low semantics despite of what's written in device tree. Allowing
device tree to override that only opens possibility for errors and does
not add any value.
Additionally, use _cansleep version to make things work with i2c-gpio
and other sleeping gpio drivers.
The reset gpio comes from platform hence it should be handled by DTS.
In driver the gpio should not be raw.
Even the hi8435 is active low but platform may invert signal (f.e. by
adding trigger on the circuit path).
I see. However - isn't this pure theoretic? Does such case exist?
I assure you that this is frequently used.
Simply search google for "simple voltage level shifter"
It might be on PNP or NPN transistor, hence logic might be inverted.
In vast majority of cases, GPIO polarity is chip-specific, not
chip-use-specific. Thus this knowlege belongs to driver and not to
device tree describing particular chip usage. Having this always
defined at usage side is IMO major source of errors.
GPIO comes from SoC then "circuit path" and finally chip reset input.
What do you propose if h/w circuit path has simple voltage level shifter
on transistor. How to differentiate PNP and NPN cases?
Regards,
Vladimir
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