From 1b801508baf58b8053bb30d101efce018b159a5e Mon Sep 17 00:00:00 2001
From: Kevin O'Connor <kevin@koconnor.net>
Date: Tue, 12 Oct 2021 13:32:46 -0400
Subject: [PATCH] stm32: Add comments to configuration of OSPEEDR gpio speed

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
---
 src/stm32/stm32f0.c |  4 +++-
 src/stm32/stm32f1.c | 11 ++++++-----
 src/stm32/stm32f4.c |  4 +++-
 src/stm32/stm32h7.c |  4 +++-
 4 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/src/stm32/stm32f0.c b/src/stm32/stm32f0.c
index a2a3a52f..06b5d3ab 100644
--- a/src/stm32/stm32f0.c
+++ b/src/stm32/stm32f0.c
@@ -64,6 +64,8 @@ gpio_clock_enable(GPIO_TypeDef *regs)
     RCC->AHBENR;
 }
 
+#define STM_OSPEED 0x2 // ~2Mhz at 50pF
+
 // Set the mode and extended function of a pin
 void
 gpio_peripheral(uint32_t gpio, uint32_t mode, int pullup)
@@ -84,7 +86,7 @@ gpio_peripheral(uint32_t gpio, uint32_t mode, int pullup)
     regs->MODER = (regs->MODER & ~m_msk) | (mode_bits << m_shift);
     regs->PUPDR = (regs->PUPDR & ~m_msk) | (pup << m_shift);
     regs->OTYPER = (regs->OTYPER & ~(1 << pos)) | (od << pos);
-    regs->OSPEEDR = (regs->OSPEEDR & ~m_msk) | (0x02 << m_shift);
+    regs->OSPEEDR = (regs->OSPEEDR & ~m_msk) | (STM_OSPEED << m_shift);
 }
 
 #define USB_BOOT_FLAG_ADDR (CONFIG_RAM_START + CONFIG_RAM_SIZE - 1024)
diff --git a/src/stm32/stm32f1.c b/src/stm32/stm32f1.c
index c0ae35fa..88500165 100644
--- a/src/stm32/stm32f1.c
+++ b/src/stm32/stm32f1.c
@@ -68,7 +68,6 @@ gpio_clock_enable(GPIO_TypeDef *regs)
     RCC->APB2ENR;
 }
 
-
 static void stm32f1_alternative_remap(uint32_t mapr_mask, uint32_t mapr_value)
 {
     // The MAPR register is a mix of write only and r/w bits
@@ -80,6 +79,8 @@ static void stm32f1_alternative_remap(uint32_t mapr_mask, uint32_t mapr_value)
     AFIO->MAPR = mapr;
 }
 
+#define STM_OSPEED 0x1 // ~10Mhz at 50pF
+
 // Set the mode and extended function of a pin
 void
 gpio_peripheral(uint32_t gpio, uint32_t mode, int pullup)
@@ -94,20 +95,20 @@ gpio_peripheral(uint32_t gpio, uint32_t mode, int pullup)
     if (mode == GPIO_INPUT) {
         cfg = pullup ? 0x8 : 0x4;
     } else if (mode == GPIO_OUTPUT) {
-        cfg = 0x1;
+        cfg = STM_OSPEED;
     } else if (mode == (GPIO_OUTPUT | GPIO_OPEN_DRAIN)) {
-        cfg = 0x5;
+        cfg = 0x4 | STM_OSPEED;
     } else if (mode == GPIO_ANALOG) {
         cfg = 0x0;
     } else {
         if (mode & GPIO_OPEN_DRAIN)
             // Alternate function with open-drain mode
-            cfg = 0xd;
+            cfg = 0xc | STM_OSPEED;
         else if (pullup > 0)
             // Alternate function input pins use GPIO_INPUT mode on the stm32f1
             cfg = 0x8;
         else
-            cfg = 0x9;
+            cfg = 0x8 | STM_OSPEED;
     }
     if (pos & 0x8)
         regs->CRH = (regs->CRH & ~msk) | (cfg << shift);
diff --git a/src/stm32/stm32f4.c b/src/stm32/stm32f4.c
index 06312832..6cbfd22a 100644
--- a/src/stm32/stm32f4.c
+++ b/src/stm32/stm32f4.c
@@ -68,6 +68,8 @@ gpio_clock_enable(GPIO_TypeDef *regs)
     RCC->AHB1ENR;
 }
 
+#define STM_OSPEED 0x2 // ~50Mhz at 40pF on STM32F4 (~25Mhz at 40pF on STM32F2)
+
 // Set the mode and extended function of a pin
 void
 gpio_peripheral(uint32_t gpio, uint32_t mode, int pullup)
@@ -88,7 +90,7 @@ gpio_peripheral(uint32_t gpio, uint32_t mode, int pullup)
     regs->MODER = (regs->MODER & ~m_msk) | (mode_bits << m_shift);
     regs->PUPDR = (regs->PUPDR & ~m_msk) | (pup << m_shift);
     regs->OTYPER = (regs->OTYPER & ~(1 << pos)) | (od << pos);
-    regs->OSPEEDR = (regs->OSPEEDR & ~m_msk) | (0x02 << m_shift);
+    regs->OSPEEDR = (regs->OSPEEDR & ~m_msk) | (STM_OSPEED << m_shift);
 }
 
 #define USB_BOOT_FLAG_ADDR (CONFIG_RAM_START + CONFIG_RAM_SIZE - 4096)
diff --git a/src/stm32/stm32h7.c b/src/stm32/stm32h7.c
index c89dd9c5..f58154d7 100644
--- a/src/stm32/stm32h7.c
+++ b/src/stm32/stm32h7.c
@@ -102,6 +102,8 @@ gpio_clock_enable(GPIO_TypeDef *regs)
     enable_pclock((uint32_t)regs);
 }
 
+#define STM_OSPEED 0x2 // ~85Mhz at 50pF
+
 // Set the mode and extended function of a pin
 void
 gpio_peripheral(uint32_t gpio, uint32_t mode, int pullup)
@@ -122,7 +124,7 @@ gpio_peripheral(uint32_t gpio, uint32_t mode, int pullup)
     regs->MODER = (regs->MODER & ~m_msk) | (mode_bits << m_shift);
     regs->PUPDR = (regs->PUPDR & ~m_msk) | (pup << m_shift);
     regs->OTYPER = (regs->OTYPER & ~(1 << pos)) | (od << pos);
-    regs->OSPEEDR = (regs->OSPEEDR & ~m_msk) | (0x02 << m_shift);
+    regs->OSPEEDR = (regs->OSPEEDR & ~m_msk) | (STM_OSPEED << m_shift);
 }
 
 #if !CONFIG_STM32_CLOCK_REF_INTERNAL