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 <[email protected]> Signed-off-by: Meenakshi Aggarwal <[email protected]> --- 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 _______________________________________________ U-Boot mailing list [email protected] https://lists.denx.de/listinfo/u-boot
