linux-kernel - Re: Re: [PATCH 1/5] ARM: tegra: set up wlan clocks for tegra dt

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Date:	Thu, 5 Jul 2012 11:18:14 +0800
From:	Wei Ni <wni@...dia.com>
To:	Marc Dietrich <marvin24@....de>
CC:	Stephen Warren <swarren@...dia.com>,
	"olof@...om.net" <olof@...om.net>,
	"ccross@...roid.com" <ccross@...roid.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Laxman Dewangan <ldewangan@...dia.com>,
	"arnd@...db.de" <arnd@...db.de>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"cjb@...top.org" <cjb@...top.org>
Subject: Re: Re: [PATCH 1/5] ARM: tegra: set up wlan clocks for tegra dt

On Wed, 2012-07-04 at 19:51 +0800, Marc Dietrich wrote:
> Am Mittwoch, 4. Juli 2012, 19:23:33 schrieb Wei Ni:
> > On Wed, 2012-07-04 at 18:43 +0800, Marc Dietrich wrote:
> > > Am Mittwoch, 4. Juli 2012, 17:34:44 schrieb Wei Ni:
> > > > Set up the wlan clock tree for Tegra20 and Tegra30.
> > > > 
> > > > Signed-off-by: Wei Ni <wni@...dia.com>
> > > > ---
> > > > 
> > > >  arch/arm/mach-tegra/board-dt-tegra20.c |    1 +
> > > >  arch/arm/mach-tegra/board-dt-tegra30.c |    1 +
> > > >  2 files changed, 2 insertions(+), 0 deletions(-)
> > > > 
> > > > diff --git a/arch/arm/mach-tegra/board-dt-tegra20.c
> > > > b/arch/arm/mach-tegra/board-dt-tegra20.c index 70a19a9..fbcc7d9 100644
> > > > --- a/arch/arm/mach-tegra/board-dt-tegra20.c
> > > > +++ b/arch/arm/mach-tegra/board-dt-tegra20.c
> > > > @@ -78,6 +78,7 @@ static __initdata struct tegra_clk_init_table
> > > > tegra_dt_clk_init_table[] = { { "pll_a",      "pll_p_out1",   56448000,
> > > > 
> > > >   true },
> > > >   
> > > >  	{ "pll_a_out0", "pll_a",        11289600,       true },
> > > >  	{ "cdev1",      NULL,           0,              true },
> > > > 
> > > > +	{ "blink",      "clk_32k",      32768,          true },
> > > 
> > > what's the reason to enable this on all boards? Would it make sense to set
> > > this to "false" instead?
> > 
> > This clock is used for the wlan device, it need to be enabled, so that
> > the wlan device can be powered on, and then the mmc driver can enumerate
> > it.
> 
> My question was more why you enable it for *all* boards, even those without 
> wlan cards connected to the sdhci. Defining it, but set it to "false", would 
> give the driver the chance to enable it only on request. On the other hand, 
> the impact on additional power consumption may be too low to measure.

Yes we have thought about this issue.
In here we need to enable this clock before loading wifi driver, so that
the mmc driver can enumerate it.
This likes another thing that the SD controller should be taught how to
provide to clients, such as trigger the power/reset gpios. We had talked
about it in the:
http://www.spinics.net/lists/linux-wireless/msg92093.html

And we are trying to provide the tegra clk framework support, so at that
time we could set this clock for different boards.

So I suppose we can just dump it into the clk init tables for now.

> 
> Marc
> 
> > > 
> > > >  	{ "i2s1",       "pll_a_out0",   11289600,       false},
> > > >  	{ "i2s2",       "pll_a_out0",   11289600,       false},
> > > >  	{ NULL,		NULL,		0,		0},
> > > > 
> > > > diff --git a/arch/arm/mach-tegra/board-dt-tegra30.c
> > > > b/arch/arm/mach-tegra/board-dt-tegra30.c index 53bf60f..2d73c61 100644
> > > > --- a/arch/arm/mach-tegra/board-dt-tegra30.c
> > > > +++ b/arch/arm/mach-tegra/board-dt-tegra30.c
> > > > @@ -61,6 +61,7 @@ static __initdata struct tegra_clk_init_table
> > > > tegra_dt_clk_init_table[] = { { "pll_a_out0",	"pll_a",	11289600,	true },
> > > > 
> > > >  	{ "extern1",	"pll_a_out0",	0,		true },
> > > >  	{ "clk_out_1",	"extern1",	0,		true },
> > > > 
> > > > +	{ "blink",	"clk_32k",	32768,		true },
> > > > 
> > > >  	{ "i2s0",	"pll_a_out0",	11289600,	false},
> > > >  	{ "i2s1",	"pll_a_out0",	11289600,	false},
> > > >  	{ "i2s2",	"pll_a_out0",	11289600,	false},
> > 
> > --
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