[U-Boot] How to use the NEON instruction at u-boot?

[V, Aneesh]

Hi Kyungmin Park, 

> -----Original Message-----
> From: u-boot-bounces at lists.denx.de [mailto:u-boot-
> bounces at lists.denx.de] On Behalf Of Kyungmin Park
> Sent: Thursday, November 11, 2010 11:05 AM
> To: u-boot at lists.denx.de"
> Cc: Minkyu Kang
> Subject: [U-Boot] How to use the NEON instruction at u-boot?
> 
> Hi,
> 
> Now I'm trying to use the NEON instruction at u-boot. but it's
> failed
> and got the data abort.
> Are there any way to use the NEON instruction at u-boot?
> 
> The main purpose is to use the neon memcpy as below.
> 
>         bge         1f
>         // copies 4 bytes, destination 32-bits aligned
>         vld4.8      {d0[0], d1[0], d2[0], d3[0]}, [r1]!
>         vst4.8      {d0[0], d1[0], d2[0], d3[0]}, [r0, :32]!
> 1:      bcc         2f
> 

I am not sure if there is a valid use-case for this. But if you
are keen on using Neon you will have to enable the co-processor first. 
Here is a piece of code I wrote for doing this in another bootloader. 

#define VMSR_FPSCR_r0 dcd 0xeee80a10
#define VMRS_r0_FPSCR dcd 0xeef80a10
__asm uint32 enable_neon(void)
{
    ldr r0, =0x00F00000
    MCR p15,0,r0,c1,c0,2 // CP15 Coprocessor Access Control Register
    ldr r0, =0x40000000
    VMSR_FPSCR_r0
    VMRS_r0_FPSCR
    bx r14
}

This is written for RVCT tool chain. So you may have to convert it
for GCC. Also, my assembler didn't allow ARMv7 instructions. So, I
used DCD. You can either use .word in gcc or use the real instructions
if your assembler understands those instructions. 

> Thank you,
> Kyungmin Park
> _______________________________________________
> U-Boot mailing list
> U-Boot at lists.denx.de
> http://lists.denx.de/mailman/listinfo/u-boot