[U-Boot] [PATCH v2 7/7] Tegra30: Add/enable Cardhu build (T30 reference board)

Tom Warren
2012-12-10T17:05:51Z

Simon,

On Sat, Dec 8, 2012 at 1:00 PM, Simon Glass <sjg@chromium.org> wrote:
> Hi,
>
> On Tue, Dec 4, 2012 at 2:41 PM, Stephen Warren <swarren@wwwdotorg.org> wrote:
>> On 12/04/2012 01:40 PM, Lucas Stach wrote:
>>> Hi Tom,
>>>
>>> Am Dienstag, den 04.12.2012, 13:22 -0700 schrieb Tom Warren:
>>> [...]
>>>>
>>>>>
>>>>>> +#define V_NS16550_CLK 216000000 /* 216MHz (pllp_out0) */
>>>>>
>>>>> I thought PLL_P ran at 408MHz on Tegra30? The kernel certainly sets it
>>>>> up that way.
>>>>
>>>> See my previous reply. In the internal U-Boot repo I ported from, PLLP
>>>> was initially set to 216MHz, then sped up to 408MHz. When this first
>>>> round of patches is in, I can address going to 408MHz first thing.
>>>>
>>> Is running the PLL_P at 408MHz something which requires a lot of work?
>>> If not, please do this and fold it into this patchset. It doesn't look
>>> too nice adding things to upstream which have to be changed/removed
>>> immediately after going in.
>>
>> Naively I'd have to agree here; it seems that programming the PLL for
>> the correct rate would probably "just work" right from the outset? After
>> all, if the code runs OK with the higher rate enabled a little later in
>> boot, I see no reason it shouldn't run OK with that exact same rate the
>> whole way through.
>
> From memory, the problem was originally that we wanted to be able to
> configure the PLL speed at run time, because we we using both speeds.
> Since T30 now apparently only uses 408MHz, it should be ok to set it
> once and hard-code it.
>
> Regards,
> Simon
>
Thanks. As I remember it, it was a user-config option for early T30
boards to run at 216MHz or 408MHz. The 408MHz PLLP change generated a
lot of email traffic on what the best output clocks (pllp_out1 thru 4)
would be for the various periphs, subclocks, etc.

When I did the original bringup for upstream U-Boot on my (older)
Cardhu, I wanted to start at 216MHz first, then step up to 408MHz when
I was at a stable point. Much like when I rebuilt my Mustang - I took
it out around the block first, to be sure everything was working OK
before I took it on the highway ;)

I'm running OK at 408MHz on my Cardhu T33. I'll resubmit V3 of the
patchset in the next day or so.

Thanks,

Tom
>>
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