diff options
| author |   Alexey Brodkin <abrodkin@synopsys.com> | 2015-06-29 15:24:37 +0300 |
|---|---|---|
| committer |   Vineet Gupta <vgupta@synopsys.com> | 2015-07-06 10:12:39 +0530 |
| commit | b607eddd7122595bbcf49c00192faf3e49b142d3 (patch) | |
| tree | 0019ed4afc4437e5e7ea97b9cfd9ee359bb5baad /arch/arc | |
| parent | ARC: Kconfig: better way to disable ARC_HAS_LLSC for ARC_CPU_750D (diff) | |
| download | linux-dev-b607eddd7122595bbcf49c00192faf3e49b142d3.tar.xz linux-dev-b607eddd7122595bbcf49c00192faf3e49b142d3.zip | |
ARCv2: guard SLC DMA ops with spinlock
SLC maintenance ops need to be serialized by software as there is no
inherent buffering / quequing of aux commands. It can silently ignore a
new aux operation if previous one is still ongoing (SLC_CTRL_BUSY)
So gaurd the SLC op using a spin lock
The spin lock doesn't seem to be contended even in heavy workloads such
as iperf. On FPGA @ 75 MHz.
[1] Before this change:
============================================================
# iperf -c 10.42.0.1
------------------------------------------------------------
Client connecting to 10.42.0.1, TCP port 5001
TCP window size: 43.8 KByte (default)
------------------------------------------------------------
[ 3] local 10.42.0.110 port 38935 connected with 10.42.0.1 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 48.4 MBytes 40.6 Mbits/sec
============================================================
[2] After this change:
============================================================
# iperf -c 10.42.0.1
------------------------------------------------------------
Client connecting to 10.42.0.1, TCP port 5001
TCP window size: 43.8 KByte (default)
------------------------------------------------------------
[ 3] local 10.42.0.243 port 60248 connected with 10.42.0.1 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 47.5 MBytes 39.8 Mbits/sec
# iperf -c 10.42.0.1
------------------------------------------------------------
Client connecting to 10.42.0.1, TCP port 5001
TCP window size: 43.8 KByte (default)
------------------------------------------------------------
[ 3] local 10.42.0.243 port 60249 connected with 10.42.0.1 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 54.9 MBytes 46.0 Mbits/sec
============================================================
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: arc-linux-dev@synopsys.com
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Diffstat (limited to 'arch/arc')
| -rw-r--r-- | arch/arc/mm/cache.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/arch/arc/mm/cache.c b/arch/arc/mm/cache.c index b29d62ed4f7e..1cd6695b6ab5 100644 --- a/arch/arc/mm/cache.c +++ b/arch/arc/mm/cache.c @@ -468,10 +468,18 @@ static void __ic_line_inv_vaddr(unsigned long paddr, unsigned long vaddr, noinline void slc_op(unsigned long paddr, unsigned long sz, const int op) { #ifdef CONFIG_ISA_ARCV2 + /* + * SLC is shared between all cores and concurrent aux operations from + * multiple cores need to be serialized using a spinlock + * A concurrent operation can be silently ignored and/or the old/new + * operation can remain incomplete forever (lockup in SLC_CTRL_BUSY loop + * below) + */ + static DEFINE_SPINLOCK(lock); unsigned long flags; unsigned int ctrl; - local_irq_save(flags); + spin_lock_irqsave(&lock, flags); /* * The Region Flush operation is specified by CTRL.RGN_OP[11..9] @@ -504,7 +512,7 @@ noinline void slc_op(unsigned long paddr, unsigned long sz, const int op) while (read_aux_reg(ARC_REG_SLC_CTRL) & SLC_CTRL_BUSY); - local_irq_restore(flags); + spin_unlock_irqrestore(&lock, flags); #endif } |