@@ -782,6 +782,37 @@ static const struct coresight_ops etm4_cs_ops = {
.source_ops = &etm4_source_ops,
};
+static inline bool cpu_supports_sysreg_trace(void)
+{
+ u64 dfr0 = read_sysreg_s(SYS_ID_AA64DFR0_EL1);
+
+ return ((dfr0 >> ID_AA64DFR0_TRACEVER_SHIFT) & 0xfUL) > 0;
+}
+
+static bool etm4_init_sysreg_access(struct etmv4_drvdata *drvdata,
+ struct csdev_access *csa)
+{
+ u32 devarch;
+
+ if (!cpu_supports_sysreg_trace())
+ return false;
+
+ /*
+ * ETMs implementing sysreg access must implement TRCDEVARCH.
+ */
+ devarch = read_etm4x_sysreg_const_offset(TRCDEVARCH);
+ if ((devarch & ETM_DEVARCH_ID_MASK) != ETM_DEVARCH_ETMv4x_ARCH)
+ return false;
+ *csa = (struct csdev_access) {
+ .io_mem = false,
+ .read = etm4x_sysreg_read,
+ .write = etm4x_sysreg_write,
+ };
+
+ drvdata->arch = etm_devarch_to_arch(devarch);
+ return true;
+}
+
static bool etm4_init_iomem_access(struct etmv4_drvdata *drvdata,
struct csdev_access *csa)
{
@@ -812,9 +843,17 @@ static bool etm4_init_iomem_access(struct etmv4_drvdata *drvdata,
static bool etm4_init_csdev_access(struct etmv4_drvdata *drvdata,
struct csdev_access *csa)
{
+ /*
+ * Always choose the memory mapped io, if there is
+ * a memory map to prevent sysreg access on broken
+ * systems.
+ */
if (drvdata->base)
return etm4_init_iomem_access(drvdata, csa);
+ if (etm4_init_sysreg_access(drvdata, csa))
+ return true;
+
return false;
}