Messages in this thread | | | Subject | Re: [PATCH V1 3/4] usb: serial: f81534: add output pin control | From | "Ji-Ze Hong (Peter Hong)" <> | Date | Tue, 2 Jan 2018 11:24:26 +0800 |
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Hi Johan,
>> In this code, I'm only read/write 3 registers of 0x2ae8, 0x2a90, 0x2a80, >> but some register will read/write more than once. Should I change the >> code from port_probe() to attach() and re-write it as: >> 1: read the 3 register >> 2: change them will 12 pin desire value >> 3: write it back >> Is it ok? > > Do you expect these pins to ever be changed after probe? If not, then > perhaps it can be moved to attach(), but otherwise I guess they should > be set at port_probe(). By using shadow registers, you should be able to > reduce the number of device accesses, but perhaps it's not worth the > complexity. > > Do you have a rough idea about how long these register updates take? I > was just worried that these changes will add up to really long probe > times. >
I had measured the time of the loop in f81534_set_port_output_pin() via getnstimeofday() with 685.410 ~ 3681.682us per port, but normally with 600~800us per port. So I prefer remain the current method of f81534_set_port_output_pin(). Is it ok?
Thanks -- With Best Regards, Peter Hong
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