Re: [PATCH v3 4/6] pinctrl: Add pinctrl binding for Broadcom CapriSoCs

From: Sherman Yin
Date: Tue Dec 17 2013 - 21:02:21 EST


On 13-12-16 05:17 AM, Linus Walleij wrote:
On Sat, Dec 14, 2013 at 2:16 AM, Sherman Yin <syin@xxxxxxxxxxxx> wrote:

+- bias-pull-up: Integer. Pull up strength in Ohm:
+ 1: 1.2 kOhm
+ 2: 1.8 kOhm
+ 3: 720 Ohm
+ 4: 2.7 kOhm
+ 5: 831 Ohm
+ 6: 1.08 kOhm
+ 7: 568 Ohm


Please do not use these custom enumerators 1 thru 7.
Instead say that the argument is given in ohms, so for
example:

bias-pull-up = <12000>;

Then translate this into the proper enumerator in your
driver instead.

Ok. The 3 bits in this enumeration correspond to enabling the 3 pull up Rs
(1.2k, 1.8k, 2.7k) in parallel, so the enum kind of make sense. But sure I
can change it to actual ohms and will error out in the driver if specified
value is not one of the 7.

Aha, that's how they do it :-)

Please write this in a comment in the driver because it makes
it a lot easier to understand what is going on, and e.g. how to
fuzz an apropriate resistance.

Yes, I plan to explain where those odd numbers come from in this file.

Can you tell me something about how such resistors are produced
in silicon?

Sorry I'm not quite sure. I only know a little bit of the circuitry down to the schematic level...

Regards,
Sherman
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