Re: [PATCH] Longhaul - Use information from Longhaul

["Rafał Bilski" <rafalbilski@interia.pl>]

[...] 
>  > Longhaul don't report minimum multiplier. It reports minimum frequency.
>  > So not always minimum multiplier at minimum FSB is really minimum.
> 
> I don't follow your logic.  How can lowest mult * lowest fsb not be
> lowest frequency ?  The MSRs most definitly only report the multipliers.

I don't know how to explain this properly in English. I will use example.
This is from my Nehemiah:
min f = 433MHz = 6.5 * 66MHz
max f = 999MHz = 7.5 * 133MHz
but this is Nehemiah "C" and it is working downto 4.0 multiplier.

This is Ezra that I have found in Google (output from Your program):
min f = 300MHz = 3.0 * 100MHz
max f = 864MHz = 6.5 * 133MHz

> 
>  > This is most important for Nehemiah witch allows FSB 66MHz, 100MHz and 
>  > 133MHz. Ezra seems to support only 100MHz and 133MHz so in this case 
>  > minimum multiplier at min FSB reported is in fact minimum PLL multiplier.
> 
> Note, that we don't (and won't) do FSB scaling even the hardware in some
> variants of longhaul claim to support it. The reality is that there are
> very few boards out there that can do it, and it's impossible to detect
> at runtime which boards they are.  Given this, all boards should always boot
> up at the fastest FSB, so the FSB we read at startup should remain constant.

I don't intend to do FSB scaling. I really don't belive that boards that don't
have hardware necesary for voltage scaling are capable of scaling FSB.
And I have removed FSB scaling capability code from my patch. Unfortunatly
I have removed to much and I lost that line.
I'm trying to be more compatible with information from Longhaul MSR. Even if 
this register is broken for my CPU, using min frequency insteed of min 
multiplier is fixing this.

> 
>  > Looks like all VIA CPUs allow to read FSB frequency from EBL_CR_POWERON.
>  > Only some have 66MHz reserved.
> 
> ISTR there was at least one (Ezra maybe?) that didn't.
> 

I don't have NDA protected information, but acording to this available to 
public both Ezra and Ezra-T have bus frequency bits.

>  > More precise speed calculations. This is bad when kernel first reports 
>  > 999MHz and we are saying later that max is 997MHz.
> 
> I'd rather keep the code readable and lose a tiny bit of accuracy here.
> The tables match the descriptions in the datasheets exactly, which makes
> it easier to review.
> 
> 		Dave
> 
> 

Come on. We are changing only two tables. Function "calc speed" must be changed
to support FSB anyway.

Rafa³


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