[PATCH v3 1/5] arm: enable allocate-on-read for LPAE's DCACHE_WRITEBACK/_WRITETHROUGH

[André Przywara]

On 07/07/2020 11:07, Ard Biesheuvel wrote:
> The LPAE versions of DCACHE_WRITEBACK and DCACHE_WRITETHROUGH are currently
> defined as no-allocate for both reads and writes, which deviates from the
> non-LPAE definition, and mostly defeats the purpose of enabling the caches
> in the first place.
> 
> So align LPAE with !LPAE, and enable allocate-on-read for both. And while
> at it, add some clarification about the meaning of the chosen values.

Many thanks for adding those comments!

> Signed-off-by: Ard Biesheuvel <ardb at kernel.org>

Verified the bits against the ARMv7 ARM.

Reviewed-by: Andre Przywara <andre.przywara at arm.com>

Cheers,
Andre.

> ---
>  arch/arm/include/asm/system.h | 23 ++++++++++++++++----
>  1 file changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
> index 7a40b56acdca..3a1501a0623c 100644
> --- a/arch/arm/include/asm/system.h
> +++ b/arch/arm/include/asm/system.h
> @@ -442,10 +442,16 @@ static inline void set_dacr(unsigned int val)
>  #define TTBCR_EPD0		(0 << 7)
>  
>  /*
> - * Memory types
> + * VMSAv8-32 Long-descriptor format memory region attributes
> + * (ARM Architecture Reference Manual section G5.7.4 [DDI0487E.a])
> + *
> + * MAIR0[ 7: 0] 0x00 Device-nGnRnE (aka Strongly-Ordered)
> + * MAIR0[15: 8] 0xaa Outer/Inner Write-Through, Read-Allocate No Write-Allocate
> + * MAIR0[23:16] 0xee Outer/Inner Write-Back, Read-Allocate No Write-Allocate
> + * MAIR0[31:24] 0xff Outer/Inner Write-Back, Read-Allocate Write-Allocate
>   */
> -#define MEMORY_ATTRIBUTES	((0x00 << (0 * 8)) | (0x88 << (1 * 8)) | \
> -				 (0xcc << (2 * 8)) | (0xff << (3 * 8)))
> +#define MEMORY_ATTRIBUTES	((0x00 << (0 * 8)) | (0xaa << (1 * 8)) | \
> +				 (0xee << (2 * 8)) | (0xff << (3 * 8)))
>  
>  /* options available for data cache on each page */
>  enum dcache_option {
> @@ -468,7 +474,16 @@ enum dcache_option {
>  #define TTB_SECT_B_MASK		(1 << 2)
>  #define TTB_SECT			(2 << 0)
>  
> -/* options available for data cache on each page */
> +/*
> + * Short-descriptor format memory region attributes, without TEX remap
> + * (ARM Architecture Reference Manual section G5.7.2 [DDI0487E.a])
> + *
> + * TEX[0] C  B
> + *   0    0  0   Device-nGnRnE (aka Strongly-Ordered)
> + *   0    1  0   Outer/Inner Write-Through, Read-Allocate No Write-Allocate
> + *   0    1  1   Outer/Inner Write-Back, Read-Allocate No Write-Allocate
> + *   1    1  1   Outer/Inner Write-Back, Read-Allocate Write-Allocate
> + */
>  enum dcache_option {
>  	DCACHE_OFF = TTB_SECT_DOMAIN(0) | TTB_SECT_XN_MASK | TTB_SECT,
>  	DCACHE_WRITETHROUGH = DCACHE_OFF | TTB_SECT_C_MASK,
>