cpu/stm32/usbdev_fs: fix EP_REG(x) assignment for toggleable bits

EP_REG(x) registers have a total of 6 toggleable bits. Those bits can only be toggled if we write a one to it, otherwise writing a zero has no effect
This commit fixes all the access to these registers to prevent from modifying these bits when not needed

Signed-off-by: Dylan Laduranty <[email protected]>

cpu/stm32/periph/usbdev_fs.c

@@ -132,6 +132,10 @@ typedef struct {
 #error "_PMA_ACCESS_SCHEME is not defined"
 #endif
 
+/* Bit mask containing all toggleable bits in a EP_REG(x) register */
+#define _EP_REG_TOGGLE_ONLY_BITS_MASK (USB_EP_DTOG_TX | USB_EP_DTOG_RX | \
+                                       USB_EPTX_STAT  | USB_EPRX_STAT  )
+
 #define EP_DESC ((ep_buf_desc_t*)USB1_PMAADDR)
 #define EP_REG(x) (*((volatile uint32_t*) (((uintptr_t)(USB)) + (4*x))))
 
@@ -313,8 +317,9 @@ void USBDEV_ISR(void) {
         unsigned epnum = irq_status & 0x000F;
         usbdev_ep_t *ep = (irq_status & USB_ISTR_DIR) ? &_ep_out[epnum] : &_ep_in[epnum];
         /* get type and add endpoint address */
-        uint16_t reg = _type_to_reg(ep->type) | ep->num;
-
+        uint16_t reg = (_type_to_reg(ep->type) | ep->num);
+        /* Avoid toggling by mistake these bits */
+        CLRBIT(reg, (_EP_REG_TOGGLE_ONLY_BITS_MASK));
         if (irq_status & USB_ISTR_DIR) {
             /* Clear RX CTR by writing 0, avoid clear TX CTR so leave it to one */
             EP_REG(epnum) = reg | USB_EP_CTR_TX;
@@ -422,8 +427,10 @@ static bool _ep_check(stm32_usbdev_fs_t *usbdev, unsigned idx,
 static void _ep_enable(usbdev_ep_t *ep)
 {
     uint16_t reg = EP_REG(ep->num);
-    /* Avoid modification of the following registers */
+    /* Avoid modification of the following bits in the register as writing
+       1 has no effect on these bits */
     SETBIT(reg, USB_EP_CTR_RX | USB_EP_CTR_TX);
+    CLRBIT(reg, USB_EP_DTOG_RX | USB_EP_DTOG_TX);
     if (ep->dir == USB_EP_DIR_OUT) {
         _set_ep_out_status(&reg, USB_EP_RX_NAK);
         /* Avoid toggling the other direction */
@@ -441,7 +448,8 @@ static void _ep_enable(usbdev_ep_t *ep)
 static void _ep_disable(usbdev_ep_t *ep)
 {
     uint16_t reg = EP_REG(ep->num);
-    /* Avoid modification of the following registers */
+    /* Avoid modification of the following bits in the register as writing
+       1 has no effect on these bits */
     SETBIT(reg, USB_EP_CTR_RX | USB_EP_CTR_TX);
 
     if (ep->dir == USB_EP_DIR_OUT) {
@@ -580,16 +588,17 @@ static void _usbdev_esr(usbdev_t *dev)
 
 static void _usbdev_ep_init(usbdev_ep_t *ep)
 {
+    uint16_t reg = EP_REG(ep->num);
     /* Set endpoint type */
-    uint16_t reg  = _type_to_reg(ep->type);
-    /* Keep previous state if already set */
-    reg |= EP_REG(ep->num) & (USB_EPTX_STAT | USB_EPRX_STAT);
-    _set_ep_out_status(&reg, USB_EP_RX_VALID);
+    reg &= ~(USB_EP_TYPE_MASK);
+    reg |= _type_to_reg(ep->type);
+    /* Keep the state ouf the other endpoint direction if already sets */
+    CLRBIT(reg, _EP_REG_TOGGLE_ONLY_BITS_MASK);
     /* Assign EP address */
     reg |= (ep->num & 0x000F);
     /* Ensure interrupts are cleared */
-    reg |= USB_EP_CTR_RX | USB_EP_CTR_TX;
-
+    reg &= ~(USB_EP_CTR_RX | USB_EP_CTR_TX);
+    /* Write the configuration to the register */
     EP_REG(ep->num) = reg;
     if (ep->dir == USB_EP_DIR_IN) {
         EP_DESC[ep->num].addr_tx = _ep_in_buf[ep->num];
@@ -653,7 +662,8 @@ static int _usbdev_ep_get(usbdev_ep_t *ep, usbopt_ep_t opt,
 static void _ep_set_stall(usbdev_ep_t *ep, usbopt_enable_t enable)
 {
     uint16_t reg = EP_REG(ep->num);
-    /* Avoid modification of the following registers */
+    /* Avoid modification of the following bits in the register as writing
+       1 has no effect on these bits */
     SETBIT(reg, USB_EP_CTR_RX | USB_EP_CTR_TX);
 
     if (ep->dir == USB_EP_DIR_IN) {
@@ -742,11 +752,12 @@ static int _usbdev_ep_xmit(usbdev_ep_t *ep, uint8_t* buf, size_t len)
 {
     unsigned irq = irq_disable();
     uint16_t reg = EP_REG(ep->num);
-    /* Avoid modification of the following registers */
+    /* Avoid modification of the following bits in the register as writing
+       1 has no effect on these bits */
     SETBIT(reg, USB_EP_CTR_RX | USB_EP_CTR_TX);
     if (ep->dir == USB_EP_DIR_OUT) {
         _set_ep_out_status(&reg, USB_EP_RX_VALID);
-        _set_ep_in_status(&reg, USB_EP_TX_NAK);
+        CLRBIT(reg, USB_EPTX_STAT);
         if (len == 0) {
             len = ep->len;
         }
@@ -761,8 +772,7 @@ static int _usbdev_ep_xmit(usbdev_ep_t *ep, uint8_t* buf, size_t len)
         _app_pbuf[ep->num] = buf;
     } else {
         _set_ep_in_status(&reg, USB_EP_TX_VALID);
-        _set_ep_out_status(&reg, USB_EP_RX_VALID);
-
+        CLRBIT(reg, USB_EPRX_STAT);
         /* Transfer IN buffer content to USB PMA SRAM */
         uint16_t* pma_ptr = (uint16_t *)(USB1_PMAADDR +
                                          (EP_DESC[ep->num].addr_tx * _PMA_ACCESS_STEP_SIZE));