From: Luciano Coelho <coelho@ti.com>
To: Mike Turquette <mturquette@linaro.org>
Cc: <linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>, <balbi@ti.com>
Subject: Re: [RFC] clk: add flags to distinguish xtal clocks
Date: Fri, 5 Jul 2013 01:37:45 +0300 [thread overview]
Message-ID: <1372977465.21065.136.camel@cumari.coelho.fi> (raw)
In-Reply-To: <20130704222538.10823.2559@quantum>
On Thu, 2013-07-04 at 15:25 -0700, Mike Turquette wrote:
> Quoting Luciano Coelho (2013-07-04 14:05:12)
> > Add a flag that indicate whether the clock is a crystal or not. Since
> > no clocks set this flag right now, include an additional flag that
> > indicates whether the type is set or not. If the CLK_IS_TYPE_DEFINED
> > flag is not set, the value of the CLK_IS_TYPE_XTAL flag is undefined.
> > This ensures backwards compatibility.
> >
> > Additionally, parse a new device tree binding in clk-fixed-rate to set
> > this flag.
> >
> > Signed-off-by: Luciano Coelho <coelho@ti.com>
> > ---
> >
> > I'm not familiar with the common clock framework and I'm not
> > entirely sure the flags can be used in such a way, but to me it looks
> > reasonable, since some clock consumers may need to know what type of
> > clock is being provided.
> >
> > Specifically, the wl12xx firmware needs to know if the clock is XTAL
> > or not to handle the stabilization and boosts properly.
>
> Hi Luciano,
Hi Mike,
> I'd like clarification on one point. Is the same clock input signal used
> on the wifi chip? What I mean is, are there multiple clock inputs and
> XTAL is one, and not-XTAL is another?
This wifi chip can work with a few different clocks and some of them are
XTAL and others are not. What the chip's firmware can use is one of
these:
19.2MHz (not XTAL)
26.0MHz (not XTAL)
26.0MHz (XTAL)
38.4MHz (not XTAL)
38.4MHz (XTAL)
52.0MHz (not XTAL)
It treats the XTAL clocks differently (but I don't really understand
enough of the details), so the driver needs to configure the firmware
according to these values.
> Or is it the same clock input and basically the problem is that you need
> to know what kind of waveform to expect (e.g. square versus sine)?
It's the same clock input in the chip's perspective. One clock input
that can be any of the combinations I mentioned above. Again, I'm not
familiar with clocks, so I guess the square vs. sine explanation is
plausible. What I could see in the firmware is that it handles the
clocks differently if they're xtal or not.
--
Luca.
next prev parent reply other threads:[~2013-07-04 22:38 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-04 21:05 [RFC] clk: add flags to distinguish xtal clocks Luciano Coelho
[not found] ` <20130704222538.10823.2559@quantum>
2013-07-04 22:37 ` Luciano Coelho [this message]
[not found] ` <20130704231953.10823.94331@quantum>
2013-07-05 7:54 ` Luciano Coelho
2013-07-29 13:50 ` Luciano Coelho
[not found] ` <20131007074424.7445.52119@quantum>
2013-10-08 15:27 ` Felipe Balbi
2013-10-16 10:24 ` Luca Coelho
2013-10-23 9:24 ` Mike Turquette
2013-10-23 11:35 ` Luca Coelho
2013-11-08 18:00 ` [PATCH] " Felipe Balbi
2013-11-08 19:16 ` Luca Coelho
2013-11-10 11:37 ` Maxime Ripard
2013-11-11 19:42 ` Felipe Balbi
2013-11-11 19:50 ` Luca Coelho
2013-11-11 20:59 ` Maxime Ripard
2013-11-12 8:05 ` Luca Coelho
2013-11-13 14:40 ` Maxime Ripard
2013-11-11 20:54 ` Maxime Ripard
2013-11-11 16:27 ` Stephen Warren
2013-11-11 19:43 ` Felipe Balbi
2013-07-05 13:12 ` [RFC] " James Hogan
2013-07-05 13:21 ` Felipe Balbi
2013-07-05 13:22 ` Luciano Coelho
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