From d2b78eddec97cdcf82f119b44fc503571517358e Mon Sep 17 00:00:00 2001
From: ziggurat29 <dev@ziggurat29.com>
Date: Thu, 9 Jun 2016 11:26:36 -0500
Subject: [PATCH] need to be able to explicitly indicate Vddusb is valid in
 order to use the OTFS block in this chip; done via PWR CR2 bit USV.

---
 arch/arm/src/stm32l4/stm32l4_pwr.c | 48 +++++++++++++++++++++++++++++-
 arch/arm/src/stm32l4/stm32l4_pwr.h | 18 +++++++++++
 2 files changed, 65 insertions(+), 1 deletion(-)

diff --git a/arch/arm/src/stm32l4/stm32l4_pwr.c b/arch/arm/src/stm32l4/stm32l4_pwr.c
index 7659f731470..bc9a022fa09 100644
--- a/arch/arm/src/stm32l4/stm32l4_pwr.c
+++ b/arch/arm/src/stm32l4/stm32l4_pwr.c
@@ -138,7 +138,7 @@ bool stm32l4_pwr_enablebkp(bool writable)
   uint16_t regval;
   bool waswritable;
 
-  /* Get the current state of the STM32 PWR control register */
+  /* Get the current state of the STM32L4 PWR control register 1 */
 
   regval      = stm32l4_pwr_getreg(STM32L4_PWR_CR1_OFFSET);
   waswritable = ((regval & PWR_CR1_DBP) != 0);
@@ -166,3 +166,49 @@ bool stm32l4_pwr_enablebkp(bool writable)
 
   return waswritable;
 }
+
+/************************************************************************************
+ * Name: stm32l4_pwr_enableusv
+ *
+ * Description:
+ *   Enables or disables the USB Supply Valid monitoring.  Setting this bit is
+ *   mandatory to use the USB OTG FS peripheral.
+ *
+ * Input Parameters:
+ *   set - True: Vddusb is valid; False: Vddusb is not present. Logical and electrical
+ *         isolation is applied to ignore this supply.
+ *
+ * Returned Value:
+ *   True: The bit was previously set.
+ *
+ ************************************************************************************/
+
+bool stm32l4_pwr_enableusv(bool set)
+{
+  uint16_t regval;
+  bool wasset;
+
+  /* Get the current state of the STM32L4 PWR control register 2 */
+
+  regval      = stm32l4_pwr_getreg(STM32L4_PWR_CR2_OFFSET);
+  wasset = ((regval & PWR_CR2_USV) != 0);
+
+  /* Enable or disable the ability to write */
+
+  if (wasset && !set)
+    {
+      /* Disable the Vddusb monitoring */
+
+      regval &= ~PWR_CR2_USV;
+      stm32l4_pwr_putreg(STM32L4_PWR_CR2_OFFSET, regval);
+    }
+  else if (!wasset && set)
+    {
+      /* Enable the Vddusb monitoring */
+
+      regval |= PWR_CR2_USV;
+      stm32l4_pwr_putreg(STM32L4_PWR_CR2_OFFSET, regval);
+    }
+
+  return wasset;
+}
diff --git a/arch/arm/src/stm32l4/stm32l4_pwr.h b/arch/arm/src/stm32l4/stm32l4_pwr.h
index 6c065f3d442..14891fe00a4 100644
--- a/arch/arm/src/stm32l4/stm32l4_pwr.h
+++ b/arch/arm/src/stm32l4/stm32l4_pwr.h
@@ -101,6 +101,24 @@ bool stm32l4_pwr_enableclk(bool enable);
 
 bool stm32l4_pwr_enablebkp(bool writable);
 
+/************************************************************************************
+ * Name: stm32l4_pwr_enableusv
+ *
+ * Description:
+ *   Enables or disables the USB Supply Valid monitoring.  Setting this bit is
+ *   mandatory to use the USB OTG FS peripheral.
+ *
+ * Input Parameters:
+ *   set - True: Vddusb is valid; False: Vddusb is not present. Logical and electrical
+ *         isolation is applied to ignore this supply.
+ *
+ * Returned Value:
+ *   True: The bit was previously set.
+ *
+ ************************************************************************************/
+
+bool stm32l4_pwr_enableusv(bool set);
+
 #undef EXTERN
 #if defined(__cplusplus)
 }