L1NEON bit

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1

Hello ,

I am using NEON instructions.I am using previous uboot from
http://www.angstrom-distribution.org/demo/beagleboard/ means not
latest one.

Does previous uboot have L1NEON bit enable? what is effect on
performance on NEON instructions execution if this bit is not set?

what are other setting in Aux Control register can effect NEON
insruction execution?

Thanks,
rach

2

We have been aware of the L1NEON requirement since Oct 2008 so it is
highly likely that your u-boot is setting L1NEON correctly.

3

Hi,

4

Rach <rachit81@gmail.com> writes:

Hi,

> Hello ,

> I am using NEON instructions.I am using previous uboot fromhttp://www.angstrom-distribution.org/demo/beagleboard/meansnot
> latest one.

We have been aware of the L1NEON requirement since Oct 2008 so it is
highly likely that your u-boot is setting L1NEON correctly.

How can I check Auxiliary Control register in User Mode that L1NEON
bit is set or not?

You can't.

Does it other way to check?

Hack the kernel to provide the value somewhere.

5

Måns Rullgård wrote:

Rach<rachit81@gmail.com> writes:

Hi,

> Hello ,

> I am using NEON instructions.I am using previous uboot fromhttp://www.angstrom-distribution.org/demo/beagleboard/meansnot
> latest one.

We have been aware of the L1NEON requirement since Oct 2008 so it is
highly likely that your u-boot is setting L1NEON correctly.

How can I check Auxiliary Control register in User Mode that L1NEON
bit is set or not?

You can't.

Does it other way to check?

Hack the kernel to provide the value somewhere.

+ unsigned long aux;
+ __asm__ __volatile__("mrc p15, 0, %0, c1, c0, 1":"=r" (aux));
+ printk("aux control: %08X\n", aux );

6

Hi Vladimir,
Thanks to help me.

7

Rach, what is the date on your u-boot (hint: you see the date as it
boots)?
It is really easiest to just update u-boot rather than patching the
kernel to try to read the auxv. No-one else has L1NEON issues any
more...

8

Hi Ian,

Rach, what is the date on your u-boot (hint: you see the date as it
boots)?

U-Boot 2009.01-00013-g52eddcd (Feb 03 2009 - 22:22:56)
Does it have L1NEON enable or L2 cache?

9

That looks like the stock uboot, which is known to break usb and dss, among other things.

regards,

Koen

10

Hi Koen,

> Hi Ian,

>> Rach, what is the date on your u-boot (hint: you see the date as it
>> boots)?
> U-Boot 2009.01-00013-g52eddcd (Feb 03 2009 - 22:22:56)
> Does it have L1NEON enable or L2 cache?

That looks like the stock uboot, which is known to break usb and dss,
among other things.

Means, Does this uboot have L1NEON and L2 cache enable?

Thanks,
rach

11

Thanks for the information. It's really interesting to know as I have been
using stock u-boot too.

Btw, http://elinux.org/BeagleBoard#U-Boot currently says
"Mainline U-Boot has good support for BeagleBoard. Get it by: ..."

Should it be updated with some kind of warning about these known issues?
And are these issues reported/documented somewhere?