[PATCH 03/10] irqchip/gic-v5: Serialise IRS synchronisation requests

[Sascha Bischoff]

IRS_SYNCR writes are ignored while IRS_SYNC_STATUSR.IDLE is clear.
Calls to gicv5_irs_syncr() for different IRQs can overlap, allowing
the second request to be dropped. Its caller can then observe the
first request completing and assume that its own events have been
processed.

Serialise the request and completion poll with a raw spinlock. We use
atomic polling, as the lock cannot be held over a sleeping wait.

Fixes: 57d72196dfc8 ("irqchip/gic-v5: Add GICv5 ITS support")
Cc: stable at vger.kernel.org
Signed-off-by: Sascha Bischoff <sascha.bischoff at arm.com>
---
 drivers/irqchip/irq-gic-v5-irs.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v5-irs.c b/drivers/irqchip/irq-gic-v5-irs.c
index 4edf787f3f97f..ead76560ea08f 100644
--- a/drivers/irqchip/irq-gic-v5-irs.c
+++ b/drivers/irqchip/irq-gic-v5-irs.c
@@ -10,6 +10,7 @@
 #include <linux/log2.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
+#include <linux/spinlock.h>
 
 #include <linux/irqchip.h>
 #include <linux/irqchip/arm-gic-v5.h>
@@ -22,6 +23,8 @@
 #define LPI_ID_BITS_LINEAR		12
 
 static DEFINE_PER_CPU_READ_MOSTLY(struct gicv5_irs_chip_data *, per_cpu_irs_data);
+/* Synchronization requests must not overlap in an IRS Domain. */
+static DEFINE_RAW_SPINLOCK(irs_sync_lock);
 static LIST_HEAD(irs_nodes);
 
 static u32 irs_readl_relaxed(struct gicv5_irs_chip_data *irs_data,
@@ -507,10 +510,11 @@ void gicv5_irs_syncr(void)
 		return;
 
 	syncr = FIELD_PREP(GICV5_IRS_SYNCR_SYNC, 1);
+	guard(raw_spinlock_irqsave)(&irs_sync_lock);
 	irs_writel_relaxed(irs_data, syncr, GICV5_IRS_SYNCR);
 
-	gicv5_wait_for_op(irs_data->irs_base, GICV5_IRS_SYNC_STATUSR,
-			  GICV5_IRS_SYNC_STATUSR_IDLE);
+	gicv5_wait_for_op_atomic(irs_data->irs_base, GICV5_IRS_SYNC_STATUSR,
+				 GICV5_IRS_SYNC_STATUSR_IDLE, NULL);
 }
 
 int gicv5_irs_register_cpu(int cpuid)

-- 
2.34.1