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authorAlexey Brodkin <abrodkin@synopsys.com>2015-06-29 15:24:37 +0300
committerVineet Gupta <vgupta@synopsys.com>2015-07-06 10:12:39 +0530
commitb607eddd7122595bbcf49c00192faf3e49b142d3 (patch)
tree0019ed4afc4437e5e7ea97b9cfd9ee359bb5baad /arch/arc/mm
parent14a0abfc4ab0b49c7e48eca5c6b31288ea457dee (diff)
downloadlinux-b607eddd7122595bbcf49c00192faf3e49b142d3.tar.bz2
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/mm')
-rw-r--r--arch/arc/mm/cache.c12
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
}