4 files changed, 133 insertions, 0 deletions

diff --git a/common_features.mk b/common_features.mk
index ecb4f5576..8338ce408 100644
--- a/common_features.mk
+++ b/common_features.mk
@@ -631,3 +631,27 @@ endif
 ifeq ($(strip $(JOYSTICK_ENABLE)), digital)
     OPT_DEFS += -DDIGITAL_JOYSTICK_ENABLE
 endif
+
+USBPD_ENABLE ?= no
+VALID_USBPD_DRIVER_TYPES = custom vendor
+USBPD_DRIVER ?= vendor
+ifeq ($(strip $(USBPD_ENABLE)), yes)
+    ifeq ($(filter $(strip $(USBPD_DRIVER)),$(VALID_USBPD_DRIVER_TYPES)),)
+        $(error USBPD_DRIVER="$(USBPD_DRIVER)" is not a valid USBPD driver)
+    else
+        OPT_DEFS += -DUSBPD_ENABLE
+        ifeq ($(strip $(USBPD_DRIVER)), vendor)
+            # Vendor-specific implementations
+            OPT_DEFS += -DUSBPD_VENDOR
+            ifeq ($(strip $(MCU_SERIES)), STM32G4xx)
+                OPT_DEFS += -DUSBPD_STM32G4
+                SRC += usbpd_stm32g4.c
+            else
+                $(error There is no vendor-provided USBPD driver available)
+            endif
+        else ifeq ($(strip $(USBPD_DRIVER)), custom)
+            OPT_DEFS += -DUSBPD_CUSTOM
+            # Board designers can add their own driver to $(SRC)
+        endif
+    endif
+endif
\ No newline at end of file
diff --git a/drivers/chibios/usbpd_stm32g4.c b/drivers/chibios/usbpd_stm32g4.c
new file mode 100644
index 000000000..54c1e1fb3
--- /dev/null
+++ b/drivers/chibios/usbpd_stm32g4.c
@@ -0,0 +1,76 @@
+/* Copyright 2021 Nick Brassel (@tzarc)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <quantum.h>
+
+#ifndef USBPD_UCPD1_CFG1
+#    define USBPD_UCPD1_CFG1 (UCPD_CFG1_PSC_UCPDCLK_0 | UCPD_CFG1_TRANSWIN_3 | UCPD_CFG1_IFRGAP_4 | UCPD_CFG1_HBITCLKDIV_4)
+#endif  // USBPD_UCPD1_CFG1
+
+// Initialises the USBPD subsystem
+__attribute__((weak)) void usbpd_init(void) {
+    // Disable dead-battery signals
+    PWR->CR3 |= PWR_CR3_UCPD_DBDIS;
+    // Enable the clock for the UCPD1 peripheral
+    RCC->APB1ENR2 |= RCC_APB1ENR2_UCPD1EN;
+
+    // Copy the existing value
+    uint32_t CFG1 = UCPD1->CFG1;
+    // Force-disable UCPD1 before configuring
+    CFG1 &= ~UCPD_CFG1_UCPDEN;
+    // Configure UCPD1
+    CFG1 = USBPD_UCPD1_CFG1;
+    // Apply the changes
+    UCPD1->CFG1 = CFG1;
+    // Enable UCPD1
+    UCPD1->CFG1 |= UCPD_CFG1_UCPDEN;
+
+    // Copy the existing value
+    uint32_t CR = UCPD1->CR;
+    // Clear out ANASUBMODE (irrelevant as a sink device)
+    CR &= ~UCPD_CR_ANASUBMODE_Msk;
+    // Advertise our capabilities as a sink, with both CC lines enabled
+    CR |= UCPD_CR_ANAMODE | UCPD_CR_CCENABLE_Msk;
+    // Apply the changes
+    UCPD1->CR = CR;
+}
+
+// Gets the current state of the USBPD allowance
+__attribute__((weak)) usbpd_allowance_t usbpd_get_allowance(void) {
+    uint32_t CR = UCPD1->CR;
+
+    int ucpd_enabled = (UCPD1->CFG1 & UCPD_CFG1_UCPDEN_Msk) >> UCPD_CFG1_UCPDEN_Pos;
+    int anamode      = (CR & UCPD_CR_ANAMODE_Msk) >> UCPD_CR_ANAMODE_Pos;
+    int cc_enabled   = (CR & UCPD_CR_CCENABLE_Msk) >> UCPD_CR_CCENABLE_Pos;
+
+    if (ucpd_enabled && anamode && cc_enabled) {
+        uint32_t SR         = UCPD1->SR;
+        int      vstate_cc1 = (SR & UCPD_SR_TYPEC_VSTATE_CC1_Msk) >> UCPD_SR_TYPEC_VSTATE_CC1_Pos;
+        int      vstate_cc2 = (SR & UCPD_SR_TYPEC_VSTATE_CC2_Msk) >> UCPD_SR_TYPEC_VSTATE_CC2_Pos;
+        int      vstate_max = vstate_cc1 > vstate_cc2 ? vstate_cc1 : vstate_cc2;
+        switch (vstate_max) {
+            case 0:
+            case 1:
+                return USBPD_500MA; // Note that this is 500mA (i.e. max USB 2.0), not 900mA, as we're not using USB 3.1 as a sink device.
+            case 2:
+                return USBPD_1500MA;
+            case 3:
+                return USBPD_3000MA;
+        }
+    }
+
+    return USBPD_500MA;
+}
\ No newline at end of file
diff --git a/drivers/usbpd.h b/drivers/usbpd.h
new file mode 100644
index 000000000..df4f29bb9
--- /dev/null
+++ b/drivers/usbpd.h
@@ -0,0 +1,29 @@
+/* Copyright 2021 Nick Brassel (@tzarc)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+typedef enum {
+    USBPD_500MA,
+    USBPD_1500MA,
+    USBPD_3000MA,
+} usbpd_allowance_t;
+
+// Initialises the USBPD subsystem
+void usbpd_init(void);
+
+// Gets the current state of the USBPD allowance
+usbpd_allowance_t usbpd_get_allowance(void);
\ No newline at end of file
diff --git a/quantum/quantum.h b/quantum/quantum.h
index 370a65fe0..b7bf5be31 100644
--- a/quantum/quantum.h
+++ b/quantum/quantum.h
@@ -193,6 +193,10 @@ extern layer_state_t layer_state;
 #    include "wpm.h"
 #endif
 
+#ifdef USBPD_ENABLE
+#    include "usbpd.h"
+#endif
+
 // Function substitutions to ease GPIO manipulation
 #if defined(__AVR__)
 typedef uint8_t pin_t;