[PATCH v3] ARC: mm: Update ARC_REG_*C_PTAG on each cacheline operation

[PATCH v3] ARC: mm: Update ARC_REG_*C_PTAG on each cacheline operation

[Barbaros Tokaoglu]

For 16 kB data cache with 4 ways and 32 byte cache lines we have tag LSB
[(128 locations for each way: 7 bits) + byte offset (32 bytes: 5 bits)]
lower than page offset (13 bits for 8 kB pages).
So it is possible for PTAG to change even for single page loop. Hence
update ARC_REG_*C_PTAG register on each cacheline iteration.

Signed-off-by: Barbaros Tokaoglu <btokaoglu@airspan.com>
---
 arch/arc/mm/cache.c | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/arch/arc/mm/cache.c b/arch/arc/mm/cache.c
index 8aa1231..d0875a8 100644
--- a/arch/arc/mm/cache.c
+++ b/arch/arc/mm/cache.c
@@ -251,13 +251,6 @@ void __cache_line_loop_v3(phys_addr_t paddr, unsigned long vaddr,
 	num_lines = DIV_ROUND_UP(sz, L1_CACHE_BYTES);
 
 	/*
-	 * MMUv3, cache ops require paddr in PTAG reg
-	 * if V-P const for loop, PTAG can be written once outside loop
-	 */
-	if (full_page)
-		write_aux_reg(aux_tag, paddr);
-
-	/*
 	 * This is technically for MMU v4, using the MMU v3 programming model
 	 * Special work for HS38 aliasing I-cache configuration with PAE40
 	 *   - upper 8 bits of paddr need to be written into PTAG_HI
@@ -268,10 +261,8 @@ void __cache_line_loop_v3(phys_addr_t paddr, unsigned long vaddr,
 		write_aux_reg(ARC_REG_IC_PTAG_HI, (u64)paddr >> 32);
 
 	while (num_lines-- > 0) {
-		if (!full_page) {
-			write_aux_reg(aux_tag, paddr);
-			paddr += L1_CACHE_BYTES;
-		}
+		write_aux_reg(aux_tag, paddr);
+		paddr += L1_CACHE_BYTES;
 
 		write_aux_reg(aux_cmd, vaddr);
 		vaddr += L1_CACHE_BYTES;
-- 
2.7.4


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RE: [PATCH v3] ARC: mm: Update ARC_REG_*C_PTAG on each cacheline operation

[Vladimir Isaev]

On Dec 15, 2021 5:13 PM, Barbaros Tokaoglu wrote:
> For 16 kB data cache with 4 ways and 32 byte cache lines we have tag LSB
> [(128 locations for each way: 7 bits) + byte offset (32 bytes: 5 bits)]
> lower than page offset (13 bits for 8 kB pages).
> So it is possible for PTAG to change even for single page loop. Hence
> update ARC_REG_*C_PTAG register on each cacheline iteration.
> 
> Signed-off-by: Barbaros Tokaoglu <btokaoglu@airspan.com>
> ---
>  arch/arc/mm/cache.c | 13 ++-----------
>  1 file changed, 2 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/arc/mm/cache.c b/arch/arc/mm/cache.c
> index 8aa1231..d0875a8 100644
> --- a/arch/arc/mm/cache.c
> +++ b/arch/arc/mm/cache.c
> @@ -251,13 +251,6 @@ void __cache_line_loop_v3(phys_addr_t paddr,
> unsigned long vaddr,
>  	num_lines = DIV_ROUND_UP(sz, L1_CACHE_BYTES);
> 
>  	/*
> -	 * MMUv3, cache ops require paddr in PTAG reg
> -	 * if V-P const for loop, PTAG can be written once outside loop
> -	 */
> -	if (full_page)
> -		write_aux_reg(aux_tag, paddr);
> -
> -	/*
>  	 * This is technically for MMU v4, using the MMU v3 programming
> model
>  	 * Special work for HS38 aliasing I-cache configuration with PAE40
>  	 *   - upper 8 bits of paddr need to be written into PTAG_HI
> @@ -268,10 +261,8 @@ void __cache_line_loop_v3(phys_addr_t paddr,
> unsigned long vaddr,
>  		write_aux_reg(ARC_REG_IC_PTAG_HI, (u64)paddr >> 32);
> 
>  	while (num_lines-- > 0) {
> -		if (!full_page) {
> -			write_aux_reg(aux_tag, paddr);
> -			paddr += L1_CACHE_BYTES;
> -		}
> +		write_aux_reg(aux_tag, paddr);
> +		paddr += L1_CACHE_BYTES;
> 
>  		write_aux_reg(aux_cmd, vaddr);
>  		vaddr += L1_CACHE_BYTES;
> --
> 2.7.4

Reviewed-by: Vladimir Isaev <isaev@synopsys.com>

Thank you,
Vladimir Isaev

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