stm32/usb: Add support for USB suspend

This follows the basics of what is decribed in
RM0091 Reference Manual 30.5.5 Suspend/Resume events .

We call enable/disable_sleep at suspend/resume, to make
sure the EC stays awake when USB is connected and active.

We also call clock_enable/disable_module, which is stubbed on
stm32f0, but can be used on other devices in the family.

This also fixes interrupt handling in usb_interrupt, by only
clearing interrupt bits that were handled instead of resetting
them all, which is racy, and can potentially lead to issues
if reset comes soon after a resume event.

BRANCH=none
BUG=chrome-os-partner:62325
TEST=build and flash hammer, connect to chell, suspend/resume,
     and see that hammer prints USB suspend and USB resume lines.

Change-Id: Ie9d02fd4a114add3ebc98dc9393680bc9a64a522
Reviewed-on: https://chromium-review.googlesource.com/446239
Commit-Ready: Nicolas Boichat <drinkcat@chromium.org>
Tested-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

6 files changed, 84 insertions, 2 deletions

diff --git a/chip/stm32/registers.h b/chip/stm32/registers.h
index 57193b08af..4f79beb769 100644
--- a/chip/stm32/registers.h
+++ b/chip/stm32/registers.h
@@ -2157,6 +2157,10 @@ typedef volatile struct stm32_dma_regs stm32_dma_regs_t;
 #define STM32_USB_ISTR_CTR	    (1 << 15)
 
 #define STM32_USB_FNR              REG16(STM32_USB_FS_BASE + 0x48)
+
+#define STM32_USB_FNR_RXDP_RXDM_SHIFT (14)
+#define STM32_USB_FNR_RXDP_RXDM_MASK  (3 << STM32_USB_FNR_RXDP_RXDM_SHIFT)
+
 #define STM32_USB_DADDR            REG16(STM32_USB_FS_BASE + 0x4C)
 #define STM32_USB_BTABLE           REG16(STM32_USB_FS_BASE + 0x50)
 #define STM32_USB_LPMCSR           REG16(STM32_USB_FS_BASE + 0x54)
diff --git a/chip/stm32/usb-stm32f0.c b/chip/stm32/usb-stm32f0.c
index 1805c74e5e..97bb93cafd 100644
--- a/chip/stm32/usb-stm32f0.c
+++ b/chip/stm32/usb-stm32f0.c
@@ -6,10 +6,14 @@
  */
 
 #include "registers.h"
+#include "system.h"
 #include "usb_api.h"
 
 void usb_connect(void)
 {
+	/* USB is in use */
+	disable_sleep(SLEEP_MASK_USB_DEVICE);
+
 	STM32_USB_BCDR |= (1 << 15) /* DPPU */;
 }
 
@@ -17,4 +21,7 @@ void usb_disconnect(void)
 {
 	/* disable pull-up on DP to disconnect */
 	STM32_USB_BCDR &= ~(1 << 15) /* DPPU */;
+
+	/* USB is off, so sleep whenever */
+	enable_sleep(SLEEP_MASK_USB_DEVICE);
 }
diff --git a/chip/stm32/usb-stm32f3.c b/chip/stm32/usb-stm32f3.c
index 8c16bd6b4a..d81548729b 100644
--- a/chip/stm32/usb-stm32f3.c
+++ b/chip/stm32/usb-stm32f3.c
@@ -7,14 +7,21 @@
 
 #include "usb-stm32f3.h"
 
+#include "system.h"
 #include "usb_api.h"
 
 void usb_connect(void)
 {
+	/* USB is in use */
+	disable_sleep(SLEEP_MASK_USB_DEVICE);
+
 	usb_board_connect();
 }
 
 void usb_disconnect(void)
 {
 	usb_board_disconnect();
+
+	/* USB is off, so sleep whenever */
+	enable_sleep(SLEEP_MASK_USB_DEVICE);
 }
diff --git a/chip/stm32/usb-stm32l.c b/chip/stm32/usb-stm32l.c
index c5d58257cb..0fa3cd0b9d 100644
--- a/chip/stm32/usb-stm32l.c
+++ b/chip/stm32/usb-stm32l.c
@@ -6,10 +6,14 @@
  */
 
 #include "registers.h"
+#include "system.h"
 #include "usb_api.h"
 
 void usb_connect(void)
 {
+	/* USB is in use */
+	disable_sleep(SLEEP_MASK_USB_DEVICE);
+
 	STM32_SYSCFG_PMC |= 1;
 }
 
@@ -17,4 +21,7 @@ void usb_disconnect(void)
 {
 	/* disable pull-up on DP to disconnect */
 	STM32_SYSCFG_PMC &= ~1;
+
+	/* USB is off, so sleep whenever */
+	enable_sleep(SLEEP_MASK_USB_DEVICE);
 }
diff --git a/chip/stm32/usb.c b/chip/stm32/usb.c
index ea34877c6d..4cdfe0828c 100644
--- a/chip/stm32/usb.c
+++ b/chip/stm32/usb.c
@@ -12,6 +12,7 @@
 #include "hooks.h"
 #include "link_defs.h"
 #include "registers.h"
+#include "system.h"
 #include "task.h"
 #include "timer.h"
 #include "util.h"
@@ -292,6 +293,47 @@ static void usb_reset(void)
 	CPRINTF("RST EP0 %04x\n", STM32_USB_EP(0));
 }
 
+#ifdef CONFIG_USB_SUSPEND
+/* See RM0091 Reference Manual 30.5.5 Suspend/Resume events */
+static void usb_suspend(void)
+{
+	CPRINTF("USB suspend!\n");
+
+	/* Set FSUSP bit to activate suspend mode */
+	STM32_USB_CNTR |= STM32_USB_CNTR_FSUSP;
+
+	/* Set USB low power mode */
+	STM32_USB_CNTR |= STM32_USB_CNTR_LP_MODE;
+
+	clock_enable_module(MODULE_USB, 0);
+
+	/* USB is not in use anymore, we can (hopefully) sleep now. */
+	enable_sleep(SLEEP_MASK_USB_DEVICE);
+}
+
+static void usb_resume(void)
+{
+	int state = (STM32_USB_FNR & STM32_USB_FNR_RXDP_RXDM_MASK)
+			>> STM32_USB_FNR_RXDP_RXDM_SHIFT;
+
+	CPRINTF("USB resume %x\n", state);
+
+	/*
+	 * TODO(crosbug.com/p/63273): Reference manual suggests going back to
+	 * sleep if state is 10 or 11, but this seems to cause other problems
+	 * (see bug). Ignore them for now.
+	 */
+
+	clock_enable_module(MODULE_USB, 1);
+
+	/* Clear FSUSP bit to exit suspend mode */
+	STM32_USB_CNTR &= ~STM32_USB_CNTR_FSUSP;
+
+	/* USB is in use again */
+	disable_sleep(SLEEP_MASK_USB_DEVICE);
+}
+#endif /* CONFIG_USB_SUSPEND */
+
 void usb_interrupt(void)
 {
 	uint16_t status = STM32_USB_ISTR;
@@ -299,6 +341,14 @@ void usb_interrupt(void)
 	if (status & STM32_USB_ISTR_RESET)
 		usb_reset();
 
+#ifdef CONFIG_USB_SUSPEND
+	if (status & STM32_USB_ISTR_SUSP)
+		usb_suspend();
+
+	if (status & STM32_USB_ISTR_WKUP)
+		usb_resume();
+#endif
+
 	if (status & STM32_USB_ISTR_CTR) {
 		int ep = status & STM32_USB_ISTR_EP_ID_MASK;
 		if (ep < USB_EP_COUNT) {
@@ -311,8 +361,8 @@ void usb_interrupt(void)
 		/* task_set_event(, 1 << ep_task); */
 	}
 
-	/* ack interrupts */
-	STM32_USB_ISTR = 0;
+	/* ack only interrupts that we handled */
+	STM32_USB_ISTR = ~status;
 }
 DECLARE_IRQ(STM32_IRQ_USB_LP, usb_interrupt, 1);
 
@@ -350,6 +400,10 @@ void usb_init(void)
 	STM32_USB_CNTR = STM32_USB_CNTR_CTRM |
 			 STM32_USB_CNTR_PMAOVRM |
 			 STM32_USB_CNTR_ERRM |
+#ifdef CONFIG_USB_SUSPEND
+			 STM32_USB_CNTR_WKUPM |
+			 STM32_USB_CNTR_SUSPM |
+#endif
 			 STM32_USB_CNTR_RESETM;
 
 #ifdef CONFIG_USB_SERIALNO
diff --git a/include/config.h b/include/config.h
index d9597d01cd..5811e0f2b5 100644
--- a/include/config.h
+++ b/include/config.h
@@ -2442,6 +2442,9 @@
 /* Support reporting as self powered in USB configuration. */
 #undef CONFIG_USB_SELF_POWERED
 
+/* Support correct handling of USB suspend (host-initiated). */
+#undef CONFIG_USB_SUSPEND
+
 /* Default pull-up value on the USB-C ports when they are used as source. */
 #define CONFIG_USB_PD_PULLUP TYPEC_RP_1A5
 /*