[U-Boot] [PATCH v2] armv8/fsl-layerscape : Add loop to check cache status

[Meenakshi Aggarwal]

Flushing L3 cache may need variable time depending upon cache line
allocation.

Coming up with a proper timeout value would be best handled by
simulations under multiple scenarios in your actual system.
>From the purely HN-F point of view, the flush would take ~15 cycles for
a clean line, and ~22 cycles for a dirty line.  For the dirty line case,
there are many variables outside the HN-F that will increase the
duration per line.  For example, a *DBIDResp from the SN-F/SBSX,
memory controller latency, SN-F/SBSX RetryAck responses, CCN ring
congestion, CCN ring hops, etc, etc.  The worst-case timeout would
have to factor in all of these variables plus the HN-F cycles for
every line in the L3, and assuming all lines are dirty

In case if L3 is not flushed properly, system behaviour will be
erratic.

Add loop to check status of L3 cache, it insures that L3 is flushed
properly.

System will stuck in while loop if there is some issue in L3 cache
flushing.

Signed-off-by: Udit Kumar <udit.kumar at nxp.com>
Signed-off-by: Meenakshi Aggarwal <meenakshi.aggarwal at nxp.com>

---
changed for v2:
	- An increase in timeout doesn't ensure completion of
	  L3 cache flushing operation. So checking the L3 cache
	  status till it succedd.
---
 arch/arm/cpu/armv8/fsl-layerscape/lowlevel.S | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm/cpu/armv8/fsl-layerscape/lowlevel.S b/arch/arm/cpu/armv8/fsl-layerscape/lowlevel.S
index 6721a57..2ba1a51 100644
--- a/arch/arm/cpu/armv8/fsl-layerscape/lowlevel.S
+++ b/arch/arm/cpu/armv8/fsl-layerscape/lowlevel.S
@@ -414,19 +414,23 @@ ENTRY(__asm_flush_l3_dcache)
 	mov	x0, #0x1		/* HNFPSTAT_SFONLY */
 	bl	hnf_set_pstate
 
+loop1:
 	mov	x0, #0x4		/* SFONLY status */
 	bl	hnf_pstate_poll
 	cbz	x0, 1f
 	mov	x8, #1			/* timeout */
+	b      loop1
 1:
 	dsb	sy
 	mov	x0, #0x3		/* HNFPSTAT_FAM */
 	bl	hnf_set_pstate
 
+loop2:
 	mov	x0, #0xc		/* FAM status */
 	bl	hnf_pstate_poll
 	cbz	x0, 1f
 	add	x8, x8, #0x2
+	b      loop2
 1:
 	mov	x0, x8
 	mov	lr, x29
-- 
1.9.1