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    SubjectRe: [PATCH 03/10] arm/tegra: prepare clock code for multiple tegra variants
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    On Fri, Nov 18, 2011 at 12:18 PM, Stephen Warren <swarren@nvidia.com> wrote:
    > 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.

    Actually, it used on some of the chromeos platforms, in particular for
    the sdio wifi interface (see board-seaboard.c on the chromeos tree).
    Without it we don't have stable operation. I'll get the use side
    patches posted for it for 3.3.

    And yeah. I was unable to find documentation too, it required getting
    questions answered from FAEs.


    -Olof
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