From mboxrd@z Thu Jan 1 00:00:00 1970 From: syin@broadcom.com (Sherman Yin) Date: Tue, 17 Dec 2013 18:02:07 -0800 Subject: [PATCH v3 4/6] pinctrl: Add pinctrl binding for Broadcom Capri SoCs In-Reply-To: References: <1381174108-25168-1-git-send-email-syin@broadcom.com> <1386787041-6035-1-git-send-email-syin@broadcom.com> <1386787041-6035-5-git-send-email-syin@broadcom.com> <52ABB150.1030702@broadcom.com> Message-ID: <52B1021F.2010708@broadcom.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 13-12-16 05:17 AM, Linus Walleij wrote: > On Sat, Dec 14, 2013 at 2:16 AM, Sherman Yin 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