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Date: Sat, 21 Jan 2012 07:08:56 +0530 From: Thomas Abraham <thomas.abraham@...aro.org> To: Tony Lindgren <tony@...mide.com> Cc: Stephen Warren <swarren@...dia.com>, Dong Aisheng-B29396 <B29396@...escale.com>, "linus.walleij@...ricsson.com" <linus.walleij@...ricsson.com>, "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>, "rob.herring@...xeda.com" <rob.herring@...xeda.com>, "kernel@...gutronix.de" <kernel@...gutronix.de>, "cjb@...top.org" <cjb@...top.org>, "Simon Glass (sjg@...omium.org)" <sjg@...omium.org>, Dong Aisheng <dongas86@...il.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "devicetree-discuss@...ts.ozlabs.org" <devicetree-discuss@...ts.ozlabs.org> Subject: Re: Pinmux bindings proposal On 20 January 2012 23:23, Tony Lindgren <tony@...mide.com> wrote: > * Thomas Abraham <thomas.abraham@...aro.org> [120120 16:45]: >> On 20 January 2012 15:35, Tony Lindgren <tony@...mide.com> wrote: >> > * Thomas Abraham <thomas.abraham@...aro.org> [120119 10:05]: >> >> On 19 January 2012 23:50, Tony Lindgren <tony@...mide.com> wrote: >> >> >> >> I would like to understand the need for populating the >> >> pinmux/pingroups tables from dt. The question here is when we have >> >> something like >> >> >> >> pins = <&pinctrl0 0x0030 0x15 0x15 0x7>; >> >> >> >> which specifies the values that need to be written to the hardware >> >> registers, would populating pinmux/pingroup tables from dt required. >> >> The SoC specific pinctrl driver can provide a way (with the help of >> >> pinctrl core) to translate these values and write to corresponding >> >> hardware registers. Is there any particular reason for populating the >> >> pinmux/pingroups tables from dt? >> > >> > Hmm I see. Yes it's still needed as we only want to parse the DT once >> > because it's slower unless it was one time only configuration during >> > init. >> >> Ok. The time spent on searching for the pin-config property can be >> reduced by having the device driver (say, i2c) keep a pointer to all >> the pinconfig properties in its node. The next time a driver needs to >> reconfigure the pins, the search time can be reduced. The time to >> parse the property values though would still be applicable. But I >> would still not opt to build pinmux/pinconfig/pindesc tables from dt. > > Hmm that's something to consider to save memory as the node will stay > there. This would allow making all the pinctrl framework data __initdata > in some cases. You'd probably want to copy the data into the driver in > some pinctrl framework struct so you could still use pinctrl framework > functions with this data and not have to parse the node again. Is it required to use pinctrl functions when we already have the hardware register values for pinmux/pinconfig in the device nodes? I was of the opinion that we need not use pinctrl API in case of dt based boot. > > For building the tables from dt, what I have currently is building > the tables without any specific knowledge about the pinmux functions. > I'm thinking that any further knowledge for debugging etc can be done > later on using user space tools to avoid storing the data in kernel. > Ok. I will go through your patches when you post them. Thanks, Thomas. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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