RE: [PATCH v4 1/7] OMAP3: PM: Update clean_l2 to use v7_flush_dcache_all

[Santosh Shilimkar <santosh.shilimkar@ti.com>]

> -----Original Message-----
> From: linux-omap-owner@vger.kernel.org [mailto:linux-omap-
> owner@vger.kernel.org] On Behalf Of Nishanth Menon
> Sent: Sunday, December 19, 2010 4:24 AM
> To: linux-omap; linux-arm
> Cc: Jean Pihet; Kevin; Tony
> Subject: [PATCH v4 1/7] OMAP3: PM: Update clean_l2 to use
> v7_flush_dcache_all
>
> From: Richard Woodruff <r-woodruff2@ti.com>
>
> Analysis in TI kernel with ETM showed that using cache mapped flush
> in kernel instead of SO mapped flush cost drops by 65% (3.39mS down
> to 1.17mS) for clean_l2 which is used during sleep sequences.
> Overall:
> 	- speed up
> 	- unfortunately there isn't a good alternative flush method today
> 	- code reduction and less maintenance and potential bug in
> 	  unmaintained code
>
> This also fixes the bug with the clean_l2 function usage.
>
> Reported-by: Tony Lindgren <tony@atomide.com>
>
> Cc: Kevin Hilman <khilman@deeprootsystems.com>
> Cc: Tony Lindgren <tony@atomide.com>
>
> [nm@ti.com: ported rkw's proposal to 2.6.37-rc2]
> Signed-off-by: Nishanth Menon <nm@ti.com>
> Signed-off-by: Richard Woodruff <r-woodruff2@ti.com>
> ---
> (no change in this series, posted for completeness)
> v2: https://patchwork.kernel.org/patch/365222/
> v1: http://marc.info/?l=linux-omap&m=129013171325210&w=2
>  arch/arm/mach-omap2/sleep34xx.S |   79
++++++----------------------------
> ----
>  1 files changed, 13 insertions(+), 66 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/sleep34xx.S b/arch/arm/mach-
> omap2/sleep34xx.S
> index 2fb205a..2c20fcf 100644
> --- a/arch/arm/mach-omap2/sleep34xx.S
> +++ b/arch/arm/mach-omap2/sleep34xx.S
> @@ -520,72 +520,17 @@ clean_caches:
>  	cmp	r9, #1 /* Check whether L2 inval is required or not*/
>  	bne	skip_l2_inval
>  clean_l2:
> -	/* read clidr */
> -	mrc     p15, 1, r0, c0, c0, 1
> -	/* extract loc from clidr */
> -	ands    r3, r0, #0x7000000
> -	/* left align loc bit field */
> -	mov     r3, r3, lsr #23
> -	/* if loc is 0, then no need to clean */
> -	beq     finished
> -	/* start clean at cache level 0 */
> -	mov     r10, #0
> -loop1:
> -	/* work out 3x current cache level */
> -	add     r2, r10, r10, lsr #1
> -	/* extract cache type bits from clidr*/
> -	mov     r1, r0, lsr r2
> -	/* mask of the bits for current cache only */
> -	and     r1, r1, #7
> -	/* see what cache we have at this level */
> -	cmp     r1, #2
> -	/* skip if no cache, or just i-cache */
> -	blt     skip
> -	/* select current cache level in cssr */
> -	mcr     p15, 2, r10, c0, c0, 0
> -	/* isb to sych the new cssr&csidr */
> -	isb
> -	/* read the new csidr */
> -	mrc     p15, 1, r1, c0, c0, 0
> -	/* extract the length of the cache lines */
> -	and     r2, r1, #7
> -	/* add 4 (line length offset) */
> -	add     r2, r2, #4
> -	ldr     r4, assoc_mask
> -	/* find maximum number on the way size */
> -	ands    r4, r4, r1, lsr #3
> -	/* find bit position of way size increment */
> -	clz     r5, r4
> -	ldr     r7, numset_mask
> -	/* extract max number of the index size*/
> -	ands    r7, r7, r1, lsr #13
> -loop2:
> -	mov     r9, r4
> -	/* create working copy of max way size*/
> -loop3:
> -	/* factor way and cache number into r11 */
> -	orr     r11, r10, r9, lsl r5
> -	/* factor index number into r11 */
> -	orr     r11, r11, r7, lsl r2
> -	/*clean & invalidate by set/way */
> -	mcr     p15, 0, r11, c7, c10, 2
> -	/* decrement the way*/
> -	subs    r9, r9, #1
> -	bge     loop3
> -	/*decrement the index */
> -	subs    r7, r7, #1
> -	bge     loop2
> -skip:
> -	add     r10, r10, #2
> -	/* increment cache number */
> -	cmp     r3, r10
> -	bgt     loop1
> -finished:
> -	/*swith back to cache level 0 */
> -	mov     r10, #0
> -	/* select current cache level in cssr */
> -	mcr     p15, 2, r10, c0, c0, 0
> -	isb
> +	/*
> +	 * Jump out to kernel flush routine
> +	 *  - reuse that code is better
> +	 *  - it executes in a cached space so is faster than refetch per-
> block
> +	 *  - should be faster and will change with kernel
> +	 *  - 'might' have to copy address, load and jump to it
Would be good to clarify that this is needed to maintain the 'lr'
when code is executed from SRAM

> +	 */
> +	ldr r1, kernel_flush
> +	mov lr, pc
> +	bx  r1
> +
>  skip_l2_inval:
>  	/* Data memory barrier and Data sync barrier */
>  	mov     r1, #0
> @@ -668,5 +613,7 @@ cache_pred_disable_mask:
>  	.word	0xFFFFE7FB
>  control_stat:
>  	.word	CONTROL_STAT
> +kernel_flush:
> +	.word v7_flush_dcache_all
>  ENTRY(omap34xx_cpu_suspend_sz)
>  	.word	. - omap34xx_cpu_suspend

O.w
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>

> --
> 1.6.3.3
>
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