rp2: Selectively leave the USB clocks enabled in light sleep.

projectgus · projectgus · commit d6986d6319cf · 2024-05-24T18:18:35.000+10:00
Without this change going to lightsleep stops the USB peripheral clock, and can lead to either the device going into a weird state or the host deciding to issue a bus reset. This change only keeps the USB peripheral clocks enabled if the USB device is currently active and a host has configured the device. Otherwise USB clocks are disabled same as before. Increases power consumption in light sleep (measured at the USB port for a PICO board as 12-13mA without this change, and 34-35mA with this change). I think can argue that if you have a working active USB host connection, an extra 20mA is unlikely to be significant. As discussed at https://github.com/orgs/micropython/discussions/14401 This work was funded through GitHub Sponsors. Signed-off-by: Angus Gratton <angus@redyak.com.au>
diff --git a/ports/rp2/modmachine.c b/ports/rp2/modmachine.c
@@ -28,6 +28,7 @@
 // extmod/modmachine.c via MICROPY_PY_MACHINE_INCLUDEFILE.
 
 #include "py/mphal.h"
+#include "mp_usbd.h"
 #include "modmachine.h"
 #include "uart.h"
 #include "hardware/clocks.h"
@@ -134,8 +135,17 @@ static void mp_machine_lightsleep(size_t n_args, const mp_obj_t *args) {
         return;
     }
     #endif
-    // Disable USB and ADC clocks.
-    clock_stop(clk_usb);
+
+    #if MICROPY_HW_ENABLE_USBDEV
+    // Only disable the USB clock if a USB host has not configured the device
+    bool disable_usb = !tud_mounted();
+    #else
+    bool disable_usb = true;
+    #endif
+    if (disable_usb) {
+        clock_stop(clk_usb);
+    }
+
     clock_stop(clk_adc);
 
     // CLK_REF = XOSC
@@ -152,7 +162,9 @@ static void mp_machine_lightsleep(size_t n_args, const mp_obj_t *args) {
 
     // Disable PLLs.
     pll_deinit(pll_sys);
-    pll_deinit(pll_usb);
+    if (disable_usb) {
+        pll_deinit(pll_usb);
+    }
 
     // Disable ROSC.
     rosc_hw->ctrl = ROSC_CTRL_ENABLE_VALUE_DISABLE << ROSC_CTRL_ENABLE_LSB;
@@ -181,6 +193,12 @@ static void mp_machine_lightsleep(size_t n_args, const mp_obj_t *args) {
             // TODO: Use RTC alarm to wake.
             clocks_hw->sleep_en1 = 0;
         }
+
+        if (!disable_usb) {
+            clocks_hw->sleep_en0 |= CLOCKS_SLEEP_EN0_CLK_SYS_PLL_USB_BITS;
+            clocks_hw->sleep_en1 |= CLOCKS_SLEEP_EN1_CLK_USB_USBCTRL_BITS;
+        }
+
         scb_hw->scr |= M0PLUS_SCR_SLEEPDEEP_BITS;
         __wfi();
         scb_hw->scr &= ~M0PLUS_SCR_SLEEPDEEP_BITS;
