linux-kernel - RE: [PATCH 03/10] arm/tegra: prepare clock code for multiple tegra variants

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Date:	Fri, 18 Nov 2011 12:18:40 -0800
From:	Stephen Warren <swarren@...dia.com>
To:	Olof Johansson <olof@...om.net>,
	Peter De Schrijver <pdeschrijver@...dia.com>
CC:	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Randy Dunlap <rdunlap@...otime.net>,
	Russell King <linux@....linux.org.uk>,
	Colin Cross <ccross@...roid.com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: RE: [PATCH 03/10] arm/tegra: prepare clock code for multiple tegra
 variants

Olof Johansson wrote at Friday, November 18, 2011 12:07 PM:
> On Thu, Nov 17, 2011 at 06:19:17PM +0200, Peter De Schrijver wrote:
> > Rework the tegra20 clock code to support multiple tegra variants :
> >
> >  * remove tegra2_periph_reset_assert/tegra2_periph_reset_deassert. This
> >    functionality should be in clock.c.
> >  * compile tegra_sdmmc_tap_delay only on tegra20 as this feature will not
> >    be available in future variants.
> >  * don't export clk_measure_input_freq as its functionality is also available
> >    using clk_get_rate().
...
> > @@ -403,10 +405,11 @@ void __init tegra_init_clock(void)
> >  }
> >
> >  /*
> > - * The SDMMC controllers have extra bits in the clock source register that
> > - * adjust the delay between the clock and data to compenstate for delays
> > - * on the PCB.
> > + * The SDMMC controllers on tegra20 have extra bits in the clock source
> > + * register that adjust the delay between the clock and data to compenstate
> > + * for delays on the PCB.
> >   */
> > +#ifdef CONFIG_ARCH_TEGRA_2x_SOC
> >  void tegra_sdmmc_tap_delay(struct clk *c, int delay)
> >  {
> >  	unsigned long flags;
> > @@ -415,6 +418,7 @@ void tegra_sdmmc_tap_delay(struct clk *c, int delay)
> >  	tegra2_sdmmc_tap_delay(c, delay);
> >  	spin_unlock_irqrestore(&c->spinlock, flags);
> >  }
> > +#endif
> 
> Ifdeffing this out doesn't quite make sense. Better to do a #ifdef in the
> include file with an #else case that fills in an empty function. This
> needs to be abstracted differently for the two platforms anyway but
> that can be done separately from this. Does tegra3 have tap delay setup
> as well? (I don't have the TRM handy right now).

I vote just rip this function out altogether.

It isn't used in mainline, chromeos-2.6.38, chromeos-3.0, nor our internal
2.6.36 or 2.6.39 kernels.

Equally, I can't find any documentation of the register bits this code
touches in either Tegra20 or Tegra30 TRMs.

-- 
nvpublic

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