[PATCH v3 3/3] coresight: etm4x: Add 32-bit read/write option to split 64-bit words

[Steve Clevenger]

An Ampere Computing design decision to not support 64-bit read/write
access in the ETMv4.6 implementation.

The Ampere work around is to split ETMv4.6 64-bit register access
into 2 ea. 32-bit read/write accesses.
AC03_DEBUG_10 is described in the AmpereOne Developer Errata document:

https://solutions.amperecomputing.com/customer-connect/products/AmpereOne-device-documentation

Changes since v2:
Removed errant '\' character from end of line 1121 in coresight-etm4x.h.

Signed-off-by: Steve Clevenger <scclevenger at os.amperecomputing.com>
---
 drivers/hwtracing/coresight/coresight-etm4x.h | 58 ++++++++++++++-----
 1 file changed, 44 insertions(+), 14 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
index 434f4e95ee17..992154770556 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.h
+++ b/drivers/hwtracing/coresight/coresight-etm4x.h
@@ -539,11 +539,6 @@
 		 readl_relaxed((csa)->base + (offset)) :		\
 		 read_etm4x_sysreg_offset((offset), false)))
 
-#define etm4x_relaxed_read64(csa, offset)				\
-	((u64)((csa)->io_mem ?						\
-		 readq_relaxed((csa)->base + (offset)) :		\
-		 read_etm4x_sysreg_offset((offset), true)))
-
 #define etm4x_read32(csa, offset)					\
 	({								\
 		u32 __val = etm4x_relaxed_read32((csa), (offset));	\
@@ -567,15 +562,6 @@
 						  false);		\
 	} while (0)
 
-#define etm4x_relaxed_write64(csa, val, offset)				\
-	do {								\
-		if ((csa)->io_mem)					\
-			writeq_relaxed((val), (csa)->base + (offset));	\
-		else							\
-			write_etm4x_sysreg_offset((val), (offset),	\
-						  true);		\
-	} while (0)
-
 #define etm4x_write32(csa, val, offset)					\
 	do {								\
 		__io_bw();						\
@@ -1091,6 +1077,50 @@ void etm4_config_trace_mode(struct etmv4_config *config);
 u64 etm4x_sysreg_read(u32 offset, bool _relaxed, bool _64bit);
 void etm4x_sysreg_write(u64 val, u32 offset, bool _relaxed, bool _64bit);
 
+/* 64-bit aligned to convert 64-bit access to 2 ea. 32-bit access */
+#pragma pack(push, 8)
+
+struct etm_quad_split {
+	u32 lsw;
+	u32 msw;
+};
+
+#pragma pack(pop)
+
+static inline u64 etm4x_relaxed_read64(struct csdev_access *csa, unsigned int offset)
+{
+	if (csa->io_mem) {
+		if (csa->no_quad_mmio) {
+			/* split 64-bit reads into 2 consecutive 32-bit reads */
+			struct etm_quad_split container;
+
+			container.lsw = etm4x_read32(csa, offset);
+			container.msw = etm4x_read32(csa, offset + sizeof(u32));
+
+			return *(u64 *) &container;
+		} else
+			return readq_relaxed(csa->base + offset);
+	} else
+		return read_etm4x_sysreg_offset(offset, true);
+}
+
+static inline void etm4x_relaxed_write64(struct csdev_access *csa, u64 quad, unsigned int offset)
+{
+	if (csa->io_mem) {
+		/* split 64-bit writes into 2 consecutive 32-bit writes */
+		if (csa->no_quad_mmio) {
+			struct etm_quad_split container;
+
+			*(u64 *) &container = quad;
+
+			etm4x_relaxed_write32(csa, container.lsw, offset);
+			etm4x_relaxed_write32(csa, container.msw, offset + sizeof(u32));
+		} else
+			writeq_relaxed(quad, csa->base + offset);
+	} else
+		write_etm4x_sysreg_offset(quad, offset, true);
+}
+
 static inline bool etm4x_is_ete(struct etmv4_drvdata *drvdata)
 {
 	return drvdata->arch >= ETM_ARCH_ETE;
-- 
2.25.1