From 1acf58c08f0f29408522a99cc7ef1d6270c21c09 Mon Sep 17 00:00:00 2001
From: Damien George <damien.p.george@gmail.com>
Date: Mon, 24 Sep 2018 12:55:15 +1000
Subject: [PATCH] stm32/modmachine: Re-enable PLLSAI[1] after waking from stop
 mode.

On F7s PLLSAI is used as a 48MHz clock source if the main PLL cannot
provide such a frequency, and on L4s PLLSAI1 is always used as a clock
source for the peripherals.  This commit makes sure these PLLs are
re-enabled upon waking from stop mode so the peripherals work.

See issues #4022 and #4178 (L4 specific).
---
 ports/stm32/modmachine.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/ports/stm32/modmachine.c b/ports/stm32/modmachine.c
index 6e0c086052..7c24b08672 100644
--- a/ports/stm32/modmachine.c
+++ b/ports/stm32/modmachine.c
@@ -568,6 +568,22 @@ STATIC mp_obj_t machine_sleep(void) {
     #endif
     }
 
+    #if defined(STM32F7)
+    if (RCC->DCKCFGR2 & RCC_DCKCFGR2_CK48MSEL) {
+        // Enable PLLSAI if it is selected as 48MHz source
+        RCC->CR |= RCC_CR_PLLSAION;
+        while (!(RCC->CR & RCC_CR_PLLSAIRDY)) {
+        }
+    }
+    #endif
+
+    #if defined(STM32L4)
+    // Enable PLLSAI1 for peripherals that use it
+    RCC->CR |= RCC_CR_PLLSAI1ON;
+    while (!(RCC->CR & RCC_CR_PLLSAI1RDY)) {
+    }
+    #endif
+
     #endif
 
     return mp_const_none;