From: Shawn Guo <shawn.guo@linaro.org>
To: Tony Lindgren <tony@atomide.com>
Cc: Stephen Warren <swarren@nvidia.com>,
Dong Aisheng <dongas86@gmail.com>,
"devicetree-discuss@lists.ozlabs.org"
<devicetree-discuss@lists.ozlabs.org>,
"Linus Walleij (linus.walleij@linaro.org)"
<linus.walleij@linaro.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"rob.herring@calxeda.com" <rob.herring@calxeda.com>,
"Grant Likely (grant.likely@secretlab.ca)"
<grant.likely@secretlab.ca>,
Thomas Abraham <thomas.abraham@linaro.org>,
"kernel@pengutronix.de" <kernel@pengutronix.de>,
"Simon Glass (sjg@chromium.org)" <sjg@chromium.org>,
"cjb@laptop.org" <cjb@laptop.org>,
Dong Aisheng-B29396 <B29396@freescale.com>,
"Sascha Hauer (s.hauer@pengutronix.de)" <s.hauer@pengutronix.de>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: Pinmux bindings proposal V2
Date: Mon, 30 Jan 2012 09:56:10 +0800 [thread overview]
Message-ID: <20120130015607.GA10470@S2101-09.ap.freescale.net> (raw)
In-Reply-To: <20120127170545.GH13504@atomide.com>
On Fri, Jan 27, 2012 at 09:05:45AM -0800, Tony Lindgren wrote:
> Hi,
>
> * Shawn Guo <shawn.guo@linaro.org> [120126 22:15]:
> > On Thu, Jan 26, 2012 at 06:08:33PM -0800, Tony Lindgren wrote:
> > > * Stephen Warren <swarren@nvidia.com> [120126 11:03]:
> > ...
> > > > Second, as I mentioned before, while some of the states are certainly
> > > > PM-related, I don't think all will be, e.g. the case of running an SD
> > > > controller at different clock rates to the SD card, and needing to
> > > > set different pin parameters based on the clock rate. Is runtime PM
> > > > intended cover that kind of thing? The idea here is that the common
> > > > pinctrl binding can allow the driver to require different named states
> > > > for those different clock rate cases.
> > >
> > > For the PM related states, those should be Linux generic. For rate
> > > setting sounds like that's really something you should set up as clocks
> > > in the Tegra wrapper driver for SDHCI?
> > >
> > That's right.
> >
> > > Ideally the SDHCI driver would be completely arch independent, and
> > > then the SoC specific wrapper driver would know how to communicate to
> > > the pinmux/pinconf framwork or clock framework what it needs using
> > > Linux generic APIs.
> >
> > But that wrapper driver should not be bothered to call pinmux/pinconf
> > APIs on pin basis to change the pinctrl configuration. The elegant
> > way would be something like the following in case that it switches
> > the bus frequency from 50 MHz to 100 MHz.
> >
> > pmx = pinmux_get(dev, "esdhc_50mhz");
> > ...
> > pinmux_put(pmx);
> > pmx = pinmux_get(dev, "esdhc_100mhz");
> > ...
> >
> > The specific mux and config settings of states esdhc_50mhz and
> > esdhc_100mhz would be retrieved from device tree.
>
> Yes whatever mux names can be used, same as with clock framework
> for clock names. But that means you'll have to constantly get/put
> the mux which is not efficient.
>
The most important reason that we want to move to pinctrl subsystem
is we need its run-time configuration feature for cases like esdhc
here. I do not think the switch here is so constant to be inefficient.
> Wouldn't it be cleaner to just clk_get esdhc_clk during init, then
> do clk_set_rate on it to toggle the rates?
>
It's not an init-time switch but run-time one. That said,
sdhci_ops.set_clock will be called during run-time.
> > > So I'd rather stay out of random named states for
> > > the pins coming from device tree; If we still need them, they should
> > > be common bindings rather than things like "xyz_clock_hack".
> > >
> > The binding defines the syntax, and I do not see the necessity to
> > force the particular state name, which is really pinctrl client
> > device specific.
>
> Do you have some other custom pin state example other than the
> clock rate change example above?
>
I have another case PM related. To aggressively save power, the pins
configured for particular function during active mode need to be
muxed on gpio mode and output 0 in low-power mode.
--
Regards,
Shawn
next prev parent reply other threads:[~2012-01-30 1:44 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-20 22:22 Pinmux bindings proposal V2 Stephen Warren
2012-01-23 21:00 ` Tony Lindgren
2012-01-23 23:08 ` Stephen Warren
2012-01-24 1:20 ` Tony Lindgren
2012-01-24 22:29 ` Stephen Warren
2012-01-25 0:04 ` Tony Lindgren
2012-01-26 19:33 ` Stephen Warren
2012-01-27 2:08 ` Tony Lindgren
2012-01-27 6:57 ` Shawn Guo
2012-01-27 17:05 ` Tony Lindgren
2012-01-30 1:56 ` Shawn Guo [this message]
2012-01-30 17:20 ` Tony Lindgren
2012-01-31 1:32 ` Shawn Guo
2012-01-31 2:29 ` Tony Lindgren
2012-02-01 5:36 ` Shawn Guo
2012-01-27 17:36 ` Stephen Warren
2012-01-27 17:42 ` Tony Lindgren
2012-01-26 9:36 ` Shawn Guo
2012-01-26 17:51 ` Tony Lindgren
2012-01-27 7:19 ` Shawn Guo
2012-01-27 17:16 ` Tony Lindgren
2012-01-30 2:10 ` Shawn Guo
2012-01-30 17:43 ` Tony Lindgren
2012-01-31 1:07 ` Shawn Guo
2012-01-26 9:24 ` Shawn Guo
2012-01-26 17:42 ` Simon Glass
2012-01-27 2:21 ` Tony Lindgren
2012-01-27 15:43 ` Simon Glass
2012-01-27 17:37 ` Tony Lindgren
2012-01-27 17:51 ` Stephen Warren
2012-01-27 18:10 ` Tony Lindgren
2012-01-30 3:27 ` Shawn Guo
2012-01-30 3:13 ` Shawn Guo
2012-01-30 17:49 ` Tony Lindgren
2012-01-27 17:38 ` Stephen Warren
2012-01-27 17:29 ` Stephen Warren
2012-01-30 2:31 ` Shawn Guo
2012-02-01 14:35 ` Shawn Guo
2012-02-02 18:36 ` Stephen Warren
2012-02-02 20:07 ` Dong Aisheng
2012-02-03 14:02 ` Shawn Guo
2012-02-03 17:21 ` Dong Aisheng
2012-02-03 17:32 ` Tony Lindgren
2012-02-03 18:13 ` Dong Aisheng
2012-02-03 21:05 ` Tony Lindgren
2012-02-04 16:55 ` Dong Aisheng
2012-02-04 17:15 ` Tony Lindgren
2012-02-03 8:46 ` Shawn Guo
2012-02-13 19:58 ` Stephen Warren
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