Re: public git l2 cache off.

Koen Kooi
2008-05-06T17:02:29Z

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Op 6 mei 2008, om 18:51 heeft Woodruff, Richard het volgende geschreven:
>> Beagleboard (omap3530)
>>
>>> I'll try the latest from here on SDP with this and see if it works.
>>> There is also a difference in CR handling. I had submitted long
>>> back a fix to Russell but let it get by me as I didn't have the time
>>> to fix per his comments. I think our version was more correct then
>>> the one in place but was still lacking a bit.
>>>
>>> [*] It seems possible you could have an issue depending on what your
>>> boot loader is or isn't doing for you.
>>
>> U-boot (both 1.1.4 and 1.3.2) calls l2disable() before booting linux,
>> so linux needs to enable it. I vote for removing the l2disable() in
>> u-
>> boot, but I can see that people might be stuck with broken binary
>> bootloaders...
>
> Yes, this 'might' help for some users if it works. Traditionally
> things usually have had some complications here at multiple levels
> in both hardware and software. And yes not everyone can upgrade a
> boot loader. However, with expanding boot from MMC/SD support
> things are getting safer.
>
> The bit I was more worried about was the boot loader may not be
> invalidating secure L2 tags correctly. The method to do this
> correctly is a little different between EMU/HS and GP devices. Also
> these base methods changed some between ES1 and ES2 of the chip. I
> hope no one is using an ES1 anymore but I'm sure code remnants exist.
>
> The working code variants did some work in u-boot and some in the
> kernel to handle these conditions. The current balance today in
> working variants today has u-boot doing more work. This probably
> merges with fewer conflicts with the arm-kernel. Last I checked u-
> boot on Beagle was a based on an older version of the code and
> probably even a wider range of versions exist in the community. As
> such it's a good bet some of this is at the root of the problems you
> are seeing.

I'm currently using the u-boot Jason built (1.3.2 + beagle patches)
which disables l2 cache before boot and I switch between 2.6.22-wtbu
(which enables L2) and git HEAD (which doesn't enable L2).

regards,

Koen

>
>
> It is important to keep x-loader/u-boot/kernel somewhat in sync for
> some of these kinds of issues until the development process has
> settled down and code matured.
>
> L2 cache is a huge performance boost on an OMAP3 so it's good to get
> it. Also you really haven't validated your software if you're
> running with it off.
>
> Regards,
> Richard W.
>
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