[U-Boot] [PATCH v2] omap3: Variant and revision checks for ARM Cortex-A8 errata workarounds

[Igor Grinberg]

Hi Paul,

On 02/22/15 18:42, Paul Kocialkowski wrote:
> Not every version and revision of the Cortex-A8 ARM core requires the same
> errata workarounds. In addition, enabling those requires to have similar
> workarounds enabled in the kernel or it will cause numerous segmentation faults.
> 
> This enables those workarounds when they are needed, according to what is done
> in Linux.

Conceptually, I'm fine with the patch, but I did not look down into the
erratas and how it should be handled...

> 
> Follow-up to the discussion from July 2013:
> http://lists.denx.de/pipermail/u-boot/2013-July/158377.html

You've missed the s-o-b.

> ---
>  arch/arm/cpu/armv7/omap3/board.c | 27 +++++++++++++++++++++------
>  1 file changed, 21 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm/cpu/armv7/omap3/board.c b/arch/arm/cpu/armv7/omap3/board.c
> index 90d6ae7..a87dd2a 100644
> --- a/arch/arm/cpu/armv7/omap3/board.c
> +++ b/arch/arm/cpu/armv7/omap3/board.c
> @@ -431,14 +431,29 @@ static void omap3_update_aux_cr_secure(u32 set_bits, u32 clear_bits)
>  
>  static void omap3_setup_aux_cr(void)
>  {
> -	/* Workaround for Cortex-A8 errata: #454179 #430973
> -	 *	Set "IBE" bit
> -	 *	Set "Disable Branch Size Mispredicts" bit
> -	 * Workaround for erratum #621766
> +	u32 id, revision, variant;
> +	u32 bits = 0;
> +
> +	asm volatile ("mrc p15, 0, %0, c0, c0, 0" : "=r" (id));
> +
> +	variant = (id & 0xf00000) >> 20;
> +	revision = id & 0x0f;
> +
> +	/* Workaround for Cortex-A8 erratum: #454179 #430973

While on this, I would also fix the multi-line comment...

> +	 *	Set IBE bit
> +	 *	Set Disable Branch Size Mispredicts (DBSM) bit
> +	 */
> +	if (variant < 2)
> +		bits |= (1 << 6) | (1 << 7);
> +
> +	/* Workaround for Cortex-A8 erratum #621766

Also here.

>  	 *	Enable L1NEON bit
> -	 * ACR |= (IBE | DBSM | L1NEON) => ACR |= 0xE0
>  	 */
> -	omap3_update_aux_cr_secure(0xE0, 0);
> +	if (variant == 2 && revision == 0)
> +		bits |= (1 << 5);
> +
> +	if (bits != 0)
> +		omap3_update_aux_cr_secure(bits, 0);
>  }
>  
>  #ifndef CONFIG_SYS_L2CACHE_OFF
> 

-- 
Regards,
Igor.