[PATCH 4/4] bsp/atsam: Use TRNG for getentropy.

[Christian Mauderer]

From: Christian Mauderer <Christian.Mauderer at embedded-brains.de>

---
 c/src/lib/libbsp/arm/atsam/Makefile.am             |  4 +-
 .../libbsp/arm/atsam/entropy/getentropy_atsam.c    | 61 ++++++++++++++++++++++
 2 files changed, 64 insertions(+), 1 deletion(-)
 create mode 100644 c/src/lib/libbsp/arm/atsam/entropy/getentropy_atsam.c

diff --git a/c/src/lib/libbsp/arm/atsam/Makefile.am b/c/src/lib/libbsp/arm/atsam/Makefile.am
index 44b31284a3..e19144990a 100644
--- a/c/src/lib/libbsp/arm/atsam/Makefile.am
+++ b/c/src/lib/libbsp/arm/atsam/Makefile.am
@@ -332,7 +332,6 @@ libbsp_a_LIBADD =
 
 # Shared
 libbsp_a_SOURCES += ../../shared/bootcard.c
-libbsp_a_SOURCES += ../../shared/getentropy-cpucounter-based.c
 libbsp_a_SOURCES += ../../shared/bspclean.c
 libbsp_a_SOURCES += ../../shared/bspgetworkarea.c
 libbsp_a_SOURCES += ../../shared/bsppredriverhook.c
@@ -450,6 +449,9 @@ libbsp_a_SOURCES += spi/sc16is752.c
 libbsp_a_SOURCES += ../../shared/tod.c
 libbsp_a_SOURCES += rtc/rtc-config.c
 
+# entropy generator
+libbsp_a_SOURCES += entropy/getentropy_atsam.c
+
 # Includes
 libbsp_a_CPPFLAGS += -I$(srcdir)/../shared/CMSIS/Include
 libbsp_a_CPPFLAGS += -I$(srcdir)/libraries/libboard
diff --git a/c/src/lib/libbsp/arm/atsam/entropy/getentropy_atsam.c b/c/src/lib/libbsp/arm/atsam/entropy/getentropy_atsam.c
new file mode 100644
index 0000000000..11e24dcda1
--- /dev/null
+++ b/c/src/lib/libbsp/arm/atsam/entropy/getentropy_atsam.c
@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2017 embedded brains GmbH.  All rights reserved.
+ *
+ *  embedded brains GmbH
+ *  Dornierstr. 4
+ *  82178 Puchheim
+ *  Germany
+ *  <rtems at embedded-brains.de>
+ *
+ * The license and distribution terms for this file may be
+ * found in the file LICENSE in this distribution or at
+ * http://www.rtems.org/license/LICENSE.
+ */
+
+#include <libchip/chip.h>
+#include <unistd.h>
+#include <string.h>
+#include <rtems/sysinit.h>
+
+static void atsam_trng_enable(void)
+{
+	PMC_EnablePeripheral(ID_TRNG);
+	TRNG_Enable();
+}
+
+int getentropy(void *ptr, size_t n)
+{
+	while (n > 0) {
+		uint32_t random;
+		size_t copy;
+
+		while ((TRNG_GetStatus() & TRNG_ISR_DATRDY) == 0) {
+			/* wait */
+		}
+		random = TRNG_GetRandData();
+
+		/*
+		 * Read TRNG status one more time to avoid race condition.
+		 * Otherwise we can read (and clear) an old ready status but get
+		 * a new value. The ready status for this value wouldn't be
+		 * reset.
+		 */
+		TRNG_GetStatus();
+
+		copy = sizeof(random);
+		if (n < copy ) {
+			copy = n;
+		}
+		memcpy(ptr, &random, copy);
+		n -= copy;
+		ptr += copy;
+	}
+
+	return 0;
+}
+
+RTEMS_SYSINIT_ITEM(
+  atsam_trng_enable,
+  RTEMS_SYSINIT_DEVICE_DRIVERS,
+  RTEMS_SYSINIT_ORDER_LAST
+);
-- 
2.12.3