[U-Boot] [PATCH 2/6] ARM: tegra: Implement clk_m

[Tom Warren]

> -----Original Message-----
> From: Tom Warren
> Sent: Thursday, August 20, 2015 9:20 AM
> To: 'Stephen Warren'; Thierry Reding
> Cc: Albert Aribaud; u-boot at lists.denx.de; Stephen Warren
> Subject: RE: [U-Boot] [PATCH 2/6] ARM: tegra: Implement clk_m
> 
> Stephen/Thierry,
> 
> > -----Original Message-----
> > From: Stephen Warren [mailto:swarren at wwwdotorg.org]
> > Sent: Thursday, August 20, 2015 7:59 AM
> > To: Thierry Reding
> > Cc: Albert Aribaud; Tom Warren; u-boot at lists.denx.de; Stephen Warren
> > Subject: Re: [U-Boot] [PATCH 2/6] ARM: tegra: Implement clk_m
> >
> > On 08/20/2015 03:42 AM, Thierry Reding wrote:
> > > From: Thierry Reding <treding at nvidia.com>
> > >
> > > On currently supported SoCs, clk_m always runs at the same frequency
> > > as the oscillator input. However newer SoC generations such as
> > > Tegra210 no longer have that restriction. Prepare for that by
> > > separating clk_m from the oscillator clock and allow SoC code to
> > > override
> > the clk_m rate.
> >
> > > diff --git a/arch/arm/include/asm/arch-tegra114/clock-tables.h
> > > b/arch/arm/include/asm/arch-tegra114/clock-tables.h
> > > index d8fa0e1d2cee..3f910f5ae8b9 100644
> > > --- a/arch/arm/include/asm/arch-tegra114/clock-tables.h
> > > +++ b/arch/arm/include/asm/arch-tegra114/clock-tables.h
> > > @@ -38,6 +38,7 @@ enum clock_id {
> > >   	/* These are the base clocks (inputs to the Tegra SOC) */
> > >   	CLOCK_ID_32KHZ,
> > >   	CLOCK_ID_OSC,
> > > +	CLOCK_ID_CLK_M,
> > >
> > >   	CLOCK_ID_COUNT,	/* number of PLLs */
> > >   	CLOCK_ID_DISPLAY2,	/* placeholder */
> >
> > clock.h contains the following:
> >
> > /* Number of PLL-based clocks (i.e. not OSC or 32KHz) */
> > #define CLOCK_ID_PLL_COUNT	(CLOCK_ID_COUNT - 2)
> 
> I decremented the CLOCK_ID_COUNT for my pllinfo tables, since 32KHZ and
> OSC have no PLL params that can be configured, to remove the 2 extra,
> empty table entries.
> We can either remove it, and add 2 empty entries for OSC/32KHZ in all the
> pllinfo tables (per SoC), and then add new CLOCK_ID entries wherever, or
> have a rule that new entries here need to be above ID_32KHZ for any PLL
> needing dividers, etc., and below it for any static clock like OSC, 32KHz, etc.
> Of course, we'll need to keep track of the decrement depending on how
> many IDs are added and where. Might be easier to just have an entry for
> every CLOCK_ID, regardless.

I applied Thierry's patchset and found that adding CLK_M to the CLOCK_ID tables results in an extra empty pll_info_table entry (3 32-bit words) for each SoC.

So I can leave it as-is, or I can adjust CLOCK_ID_PLL_COUNT in clock.h to be CLOCK_ID_COUNT - 3 to account for the 3 non-configurable clocks (OSC, 32KHz and MCLK), and there'll be no extra empty data in the pll_info tables.

I'm going to go with the 2nd approach.  I've applied these (plus some from Stephen and one from Axel Lin) to u-boot-tegra/next and after some testing today I'll be pushing this to Denx for everyone to play with it before I send a PR to TomR.  So PTAL.

Thanks
 
Tom
--
nvpublic
> 
> >
> > ... which would need to be updated. Related, see internal bug number
> > 1676978 to see if any of the other gotchas there affect this patch.