From mboxrd@z Thu Jan 1 00:00:00 1970 From: tony@atomide.com (Tony Lindgren) Date: Mon, 22 Oct 2012 12:07:45 -0700 Subject: [PATCH v2] pinctrl: reserve pins when states are activated In-Reply-To: References: <1350651909-5337-1-git-send-email-linus.walleij@stericsson.com> <20121019181019.GP4730@atomide.com> Message-ID: <20121022190743.GE4730@atomide.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org * Linus Walleij [121022 01:22]: > On Fri, Oct 19, 2012 at 8:10 PM, Tony Lindgren wrote: > > [Me] > >> Instead: let use reserve the pins when the state is activated > >> and drop them when the state is disabled, i.e. when we move to > >> another state. This way different devices/functions can use the > >> same pins at different times. > > > > Hmm doesn't this mean that we are now doing lots of extra > > reserving and dropping of pins? Performance is important from > > latency point of view for cases where we need to remux pins > > constantly runtime PM. > > It is only done in case the pinmux state is switched in runtime > suspend/resume, so it's e.g. possible to just alter the pin config. > > But in general what you say is true. > > We used to to the same thing by having drivers call > pinctrl_get()/pinctrl_put() in this case instead, but that went > away with the introduction of states, so we cannot encode > different pin sets with say > pinctrl_get(dev, "foo")/pinctrl_get(dev, "bar") > anymore since there is only one pinctrl handle per device, > but multiple states. OK > If this turns out to be a severe performance bottleneck, I > suggest to add some additional constraint API, like > pinctrl_set_pinmux_homegeneous_pinsets(true) that will > at runtime select whether the pin allocation is done when > getting the pinctrl handle instead. Or maybe you could release + reserve the pins only if the pins change? Regards, Tony