diff --git a/firmware/target/arm/as3525/usb-drv-as3525.c b/firmware/target/arm/as3525/usb-drv-as3525.c
index e97abb2ca0..60c8cd7027 100644
--- a/firmware/target/arm/as3525/usb-drv-as3525.c
+++ b/firmware/target/arm/as3525/usb-drv-as3525.c
@@ -156,6 +156,14 @@ static void dma_desc_init(int ep, int dir)
 static void reset_endpoints(int init)
 {
     int i;
+    /*
+     * MPS sizes depending on speed:
+     * LS: 8 (control), no bulk available
+     * FS: 64 (control), 64 (bulk)
+     * HS: 64 (control), 512 (bulk)
+     *
+     * We don't need to handle LS since there is no low-speed only host AFAIK.
+     */
     int mps = i == 0 ? 64 : (usb_drv_port_speed() ? 512 : 64);
 
     /*