added comment note for beta chip walkaround

1 files changed, 11 insertions, 1 deletions

diff --git a/src/portable/espressif/esp32s2/dcd_esp32s2.c b/src/portable/espressif/esp32s2/dcd_esp32s2.c
index 099f3af3e..d1e670358 100644
--- a/src/portable/espressif/esp32s2/dcd_esp32s2.c
+++ b/src/portable/espressif/esp32s2/dcd_esp32s2.c
@@ -170,7 +170,17 @@ void dcd_init(uint8_t rhport)
   USB0.gusbcfg |= USB_FORCEDEVMODE_M;                    // force devmode
 
   USB0.gotgctl &= ~(USB_BVALIDOVVAL_M | USB_BVALIDOVEN_M | USB_VBVALIDOVVAL_M); //no overrides
-#ifdef CONFIG_IDF_TARGET_ESP32S2BETA // needed for beta chip only
+
+#ifdef CONFIG_IDF_TARGET_ESP32S2BETA
+  // needed for beta chip only
+  // there was a bug in the phy logic that made the chip reset as soon as it transmitted anything.
+  // Setting the B override value made it ignore resets (any resets, generated by the faulty logic or not),
+  // which 'fixed' the problem well enough to test usb with it.
+  // Also, do note that the beta silicon run was very small and software support for it is not in mainstream esp-idf,
+  // as such you may consider phasing out support for it alltogether somewhere in the future
+
+  // TODO we could safely remove this later (maybe after 2020)
+
   //C. chip 7.2.2 hack
   ESP_LOGV(TAG, "DCD init - chip ESP32-S2 beta hack");
   USB0.gotgctl = (0 << USB_BVALIDOVVAL_S); //B override value