stm32g0: add rng.

Regular rng peripheral, with one additional bit : clock error detection
apparently available on l4 chips).  Curiously, Clock error detection is
_disabled_ when bit is set, but bit is cleared by default, so peripheral
/ clock error detection behaves like all other chips..

NB: RNG need proper rcc_ccicr_rngsel bits set to work, no clock is set by
default. Note also that on that chip fRNGCLK must be higher than fHCLK/32

include/libopencm3/stm32/g0/rng.h

@@ -0,0 +1,40 @@
+/** @defgroup rng_defines RNG Defines
+ *
+ * @ingroup STM32G0xx_defines
+ *
+ * @brief <b>Defined Constants and Types for the STM32G0xx EXTI Control</b>
+ *
+ * @version 1.0.0
+ *
+ * LGPL License Terms @ref lgpl_license
+ *  */
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/**@{*/
+#ifndef LIBOPENCM3_RNG_H
+#define LIBOPENCM3_RNG_H
+
+#include <libopencm3/stm32/common/rng_common_v1.h>
+
+/* --- RNG_CR values ------------------------------------------------------- */
+
+/** Clock error detection : CED = 0 : Detection Enabled */
+#define RNG_CR_CED		(1 << 5)
+
+#endif
+/**@}*/

include/libopencm3/stm32/rng.h

@@ -30,6 +30,8 @@
 #       include <libopencm3/stm32/l0/rng.h>
 #elif defined(STM32L4)
 #       include <libopencm3/stm32/l4/rng.h>
+#elif defined(STM32G0)
+#       include <libopencm3/stm32/g0/rng.h>
 #else
 #       error "stm32 family not defined."
 #endif

lib/stm32/g0/Makefile

@@ -43,6 +43,7 @@ OBJS += iwdg_common_all.o
 OBJS += usart_common_all.o usart_common_v2.o
 OBJS += spi_common_all.o spi_common_v1_frf.o
 OBJS += i2c_common_v2.o
+OBJS += rng_common_v1.o
 
 VPATH +=../:../../cm3:../common