Andriy Gapon 155514eacf nctgpio: improve performance (latency) of operation ... This change consists of two parts. First, nctgpio now supports hardware access via an I/O port window if it's configured by firmware. For instance, PC Engines firmware v4.10.0.2 does that. This is faster than going through the Super I/O configuration registers. Second, nctgpio now caches values of bits that it controls. For example, the driver does not need to access the hardware to determine if a pin is an output or an input, or a state of an output. Also, the driver makes use of the fact that the hardware preserves an output state of a pin accross a switch to the input mode and back. With this change I am able to use the 1-Wire bus over nctgpio whereas previously the driver introduced too much latency to be compliant with the relatively strict protocol timings. superio0: <Nuvoton NCT5104D/NCT6102D/NCT6106D (rev. B+)> at port 0x2e-0x2f on isa0 gpio1: <Nuvoton GPIO controller> at GPIO ldn 0x07 on superio0 pcib0: allocated type 4 (0x220-0x226) for rid 0 of gpio1 gpiobus1: <GPIO bus> on gpio1 owc0: <GPIO attached one-wire bus> at pin 4 on gpiobus1 ow0: <1 Wire Bus> on owc0 ow0: romid 28:b2:9e:45:92:10:02:34: no driver ow_temp0: <Advanced One Wire Temperature> romid 28:b2:9e:45:92:10:02:34 on ow0 MFC after: 4 weeks		2019-10-22 14:20:35 +00:00
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nctgpio.c	nctgpio: improve performance (latency) of operation	2019-10-22 14:20:35 +00:00