irqchip: gicv3-its: Use non-cacheable accesses when no shareability

If the ITS or the redistributors report their shareability as zero,
then it is important to make sure they will no generate any cacheable
traffic, as this is unlikely to produce the expected result.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Link: https://lkml.kernel.org/r/1427465705-17126-5-git-send-email-marc.zyngier@arm.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

1 files changed, 43 insertions, 4 deletions

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 56353f6..9687f8a 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -802,6 +802,7 @@ static int its_alloc_tables(struct its_node *its)
 	int i;
 	int psz = SZ_64K;
 	u64 shr = GITS_BASER_InnerShareable;
+	u64 cache = GITS_BASER_WaWb;
 
 	for (i = 0; i < GITS_BASER_NR_REGS; i++) {
 		u64 val = readq_relaxed(its->base + GITS_BASER + i * 8);
@@ -848,7 +849,7 @@ retry_baser:
 		val = (virt_to_phys(base) 				 |
 		       (type << GITS_BASER_TYPE_SHIFT)			 |
 		       ((entry_size - 1) << GITS_BASER_ENTRY_SIZE_SHIFT) |
-		       GITS_BASER_WaWb					 |
+		       cache						 |
 		       shr						 |
 		       GITS_BASER_VALID);
 
@@ -874,9 +875,12 @@ retry_baser:
 			 * Shareability didn't stick. Just use
 			 * whatever the read reported, which is likely
 			 * to be the only thing this redistributor
-			 * supports.
+			 * supports. If that's zero, make it
+			 * non-cacheable as well.
 			 */
 			shr = tmp & GITS_BASER_SHAREABILITY_MASK;
+			if (!shr)
+				cache = GITS_BASER_nC;
 			goto retry_baser;
 		}
 
@@ -980,6 +984,17 @@ static void its_cpu_init_lpis(void)
 	tmp = readq_relaxed(rbase + GICR_PROPBASER);
 
 	if ((tmp ^ val) & GICR_PROPBASER_SHAREABILITY_MASK) {
+		if (!(tmp & GICR_PROPBASER_SHAREABILITY_MASK)) {
+			/*
+			 * The HW reports non-shareable, we must
+			 * remove the cacheability attributes as
+			 * well.
+			 */
+			val &= ~(GICR_PROPBASER_SHAREABILITY_MASK |
+				 GICR_PROPBASER_CACHEABILITY_MASK);
+			val |= GICR_PROPBASER_nC;
+			writeq_relaxed(val, rbase + GICR_PROPBASER);
+		}
 		pr_info_once("GIC: using cache flushing for LPI property table\n");
 		gic_rdists->flags |= RDIST_FLAGS_PROPBASE_NEEDS_FLUSHING;
 	}
@@ -990,6 +1005,18 @@ static void its_cpu_init_lpis(void)
 	       GICR_PENDBASER_WaWb);
 
 	writeq_relaxed(val, rbase + GICR_PENDBASER);
+	tmp = readq_relaxed(rbase + GICR_PENDBASER);
+
+	if (!(tmp & GICR_PENDBASER_SHAREABILITY_MASK)) {
+		/*
+		 * The HW reports non-shareable, we must remove the
+		 * cacheability attributes as well.
+		 */
+		val &= ~(GICR_PENDBASER_SHAREABILITY_MASK |
+			 GICR_PENDBASER_CACHEABILITY_MASK);
+		val |= GICR_PENDBASER_nC;
+		writeq_relaxed(val, rbase + GICR_PENDBASER);
+	}
 
 	/* Enable LPIs */
 	val = readl_relaxed(rbase + GICR_CTLR);
@@ -1422,14 +1449,26 @@ static int its_probe(struct device_node *node, struct irq_domain *parent)
 
 	writeq_relaxed(baser, its->base + GITS_CBASER);
 	tmp = readq_relaxed(its->base + GITS_CBASER);
-	writeq_relaxed(0, its->base + GITS_CWRITER);
-	writel_relaxed(GITS_CTLR_ENABLE, its->base + GITS_CTLR);
 
 	if ((tmp ^ baser) & GITS_CBASER_SHAREABILITY_MASK) {
+		if (!(tmp & GITS_CBASER_SHAREABILITY_MASK)) {
+			/*
+			 * The HW reports non-shareable, we must
+			 * remove the cacheability attributes as
+			 * well.
+			 */
+			baser &= ~(GITS_CBASER_SHAREABILITY_MASK |
+				   GITS_CBASER_CACHEABILITY_MASK);
+			baser |= GITS_CBASER_nC;
+			writeq_relaxed(baser, its->base + GITS_CBASER);
+		}
 		pr_info("ITS: using cache flushing for cmd queue\n");
 		its->flags |= ITS_FLAGS_CMDQ_NEEDS_FLUSHING;
 	}
 
+	writeq_relaxed(0, its->base + GITS_CWRITER);
+	writel_relaxed(GITS_CTLR_ENABLE, its->base + GITS_CTLR);
+
 	if (of_property_read_bool(its->msi_chip.of_node, "msi-controller")) {
 		its->domain = irq_domain_add_tree(NULL, &its_domain_ops, its);
 		if (!its->domain) {