stm32_fsdev: Allow configuring single-buffered isochronous endpoints.

Controlled by the embedder defining CFG_TUD_FSDEV_DOUBLE_BUFFERED_ISO_EP
in tusb_config.h. If hardware does have SBUF_ISO bit it will use only
one half of endpoint pair register.

Author: Milek7

src/portable/st/stm32_fsdev/dcd_stm32_fsdev.c

@@ -331,8 +331,13 @@ static void handle_ctr_rx(uint32_t ep_id) {
   xfer_ctl_t* xfer = xfer_ctl_ptr(ep_num, TUSB_DIR_OUT);
 
   uint8_t buf_id;
-  if (is_iso) {
-    buf_id = (ep_reg & USB_EP_DTOG_RX) ? 0 : 1; // ISO are double buffered
+#if FSDEV_USE_SBUF_ISO == 0
+  bool const dbl_buf = is_iso;
+#else
+  bool const dbl_buf = false;
+#endif
+  if (dbl_buf) {
+    buf_id = (ep_reg & USB_EP_DTOG_RX) ? 0 : 1;
   } else {
     buf_id = BTABLE_BUF_RX;
   }
@@ -527,10 +532,16 @@ static uint8_t dcd_ep_alloc(uint8_t ep_addr, uint8_t ep_type)
       return i;
     }
 
+#if FSDEV_USE_SBUF_ISO == 0
+    bool const dbl_buf = ep_type == TUSB_XFER_ISOCHRONOUS;
+#else
+    bool const dbl_buf = false;
+#endif
+
     // If EP of current direction is not allocated
-    // Except for ISO endpoint, both direction should be free
+    // For double-buffered mode both directions needs to be free
     if (!ep_alloc_status[i].allocated[dir] &&
-        (ep_type != TUSB_XFER_ISOCHRONOUS || !ep_alloc_status[i].allocated[dir ^ 1])) {
+        (!dbl_buf || !ep_alloc_status[i].allocated[dir ^ 1])) {
       // Check if EP number is the same
       if (ep_alloc_status[i].ep_num == 0xFF || ep_alloc_status[i].ep_num == epnum) {
         // One EP pair has to be the same type
@@ -652,18 +663,20 @@ bool dcd_edpt_iso_alloc(uint8_t rhport, uint8_t ep_addr, uint16_t largest_packet
   uint8_t const dir = tu_edpt_dir(ep_addr);
   uint8_t const ep_idx = dcd_ep_alloc(ep_addr, TUSB_XFER_ISOCHRONOUS);
 
-  /* Create a packet memory buffer area. Enable double buffering for devices with 2048 bytes PMA,
-     for smaller devices double buffering occupy too much space. */
-#if FSDEV_PMA_SIZE > 1024u
+#if CFG_TUD_FSDEV_DOUBLE_BUFFERED_ISO_EP != 0
   uint32_t pma_addr = dcd_pma_alloc(largest_packet_size, true);
   uint16_t pma_addr2 = pma_addr >> 16;
 #else
   uint32_t pma_addr = dcd_pma_alloc(largest_packet_size, false);
   uint16_t pma_addr2 = pma_addr;
 #endif
 
+#if FSDEV_USE_SBUF_ISO == 0
   btable_set_addr(ep_idx, 0, pma_addr);
   btable_set_addr(ep_idx, 1, pma_addr2);
+#else
+  btable_set_addr(ep_idx, dir == TUSB_DIR_IN ? BTABLE_BUF_TX : BTABLE_BUF_RX, pma_addr);
+#endif
 
   xfer_ctl_t* xfer = xfer_ctl_ptr(ep_num, dir);
   xfer->ep_idx = ep_idx;
@@ -684,10 +697,23 @@ bool dcd_edpt_iso_activate(uint8_t rhport, tusb_desc_endpoint_t const *desc_ep)
 
   uint32_t ep_reg = ep_read(ep_idx) & ~USB_EPREG_MASK;
   ep_reg |= tu_edpt_number(ep_addr) | USB_EP_ISOCHRONOUS | USB_EP_CTR_TX | USB_EP_CTR_RX;
+#if FSDEV_USE_SBUF_ISO != 0
+  ep_reg |= USB_EP_KIND;
+
+  ep_change_status(&ep_reg, dir, EP_STAT_DISABLED);
+  ep_change_dtog(&ep_reg, dir, 0);
+
+  if (dir == TUSB_DIR_IN) {
+    ep_reg &= ~(USB_EPRX_STAT | USB_EP_DTOG_RX);
+  } else {
+    ep_reg &= ~(USB_EPTX_STAT | USB_EP_DTOG_TX);
+  }
+#else
   ep_change_status(&ep_reg, TUSB_DIR_IN, EP_STAT_DISABLED);
   ep_change_status(&ep_reg, TUSB_DIR_OUT, EP_STAT_DISABLED);
   ep_change_dtog(&ep_reg, dir, 0);
   ep_change_dtog(&ep_reg, (tusb_dir_t)(1 - dir), 1);
+#endif
 
   ep_write(ep_idx, ep_reg, true);
 
@@ -702,7 +728,12 @@ static void dcd_transmit_packet(xfer_ctl_t *xfer, uint16_t ep_ix) {
   bool const is_iso = ep_is_iso(ep_reg);
 
   uint8_t buf_id;
-  if (is_iso) {
+#if FSDEV_USE_SBUF_ISO == 0
+  bool const dbl_buf = is_iso;
+#else
+  bool const dbl_buf = false;
+#endif
+  if (dbl_buf) {
     buf_id = (ep_reg & USB_EP_DTOG_TX) ? 1 : 0;
   } else {
     buf_id = BTABLE_BUF_TX;

src/portable/st/stm32_fsdev/fsdev_ch32.h

@@ -54,9 +54,14 @@
 #endif
 
 #define FSDEV_PMA_SIZE (512u)
+#define FSDEV_USE_SBUF_ISO 0
 #define FSDEV_REG_BASE  (APB1PERIPH_BASE + 0x00005C00UL)
 #define FSDEV_PMA_BASE  (APB1PERIPH_BASE + 0x00006000UL)
 
+#ifndef CFG_TUD_FSDEV_DOUBLE_BUFFERED_ISO_EP
+  #define CFG_TUD_FSDEV_DOUBLE_BUFFERED_ISO_EP 0
+#endif
+
 /****************************  ISTR interrupt events  *************************/
 #define USB_ISTR_CTR                         ((uint16_t)0x8000U)               /*!< Correct TRansfer (clear-only bit) */
 #define USB_ISTR_PMAOVR                      ((uint16_t)0x4000U)               /*!< DMA OVeR/underrun (clear-only bit) */

src/portable/st/stm32_fsdev/fsdev_stm32.h

@@ -36,6 +36,7 @@
   #include "stm32f0xx.h"
   #define FSDEV_PMA_SIZE (1024u)
   #define FSDEV_REG_BASE USB_BASE
+  #define FSDEV_HAS_SBUF_ISO 0
   // F0x2 models are crystal-less
   // All have internal D+ pull-up
   // 070RB:    2 x 16 bits/word memory     LPM Support, BCD Support
@@ -44,6 +45,7 @@
 #elif CFG_TUSB_MCU == OPT_MCU_STM32F1
   #include "stm32f1xx.h"
   #define FSDEV_PMA_SIZE (512u)
+  #define FSDEV_HAS_SBUF_ISO 0
   // NO internal Pull-ups
   //         *B, and *C:    2 x 16 bits/word
 
@@ -55,6 +57,7 @@
       defined(STM32F373xC)
   #include "stm32f3xx.h"
   #define FSDEV_PMA_SIZE (512u)
+  #define FSDEV_HAS_SBUF_ISO 0
   // NO internal Pull-ups
   //         *B, and *C:    1 x 16 bits/word
   // PMA dedicated to USB (no sharing with CAN)
@@ -64,25 +67,30 @@
       defined(STM32F303xD) || defined(STM32F303xE)
   #include "stm32f3xx.h"
   #define FSDEV_PMA_SIZE (1024u)
+  #define FSDEV_HAS_SBUF_ISO 0
   // NO internal Pull-ups
   // *6, *8, *D, and *E:    2 x 16 bits/word     LPM Support
   // When CAN clock is enabled, USB can use first 768 bytes ONLY.
 
 #elif CFG_TUSB_MCU == OPT_MCU_STM32L0
   #include "stm32l0xx.h"
   #define FSDEV_PMA_SIZE (1024u)
+  #define FSDEV_HAS_SBUF_ISO 0
 
 #elif CFG_TUSB_MCU == OPT_MCU_STM32L1
   #include "stm32l1xx.h"
   #define FSDEV_PMA_SIZE (512u)
+  #define FSDEV_HAS_SBUF_ISO 0
 
 #elif CFG_TUSB_MCU == OPT_MCU_STM32G4
   #include "stm32g4xx.h"
   #define FSDEV_PMA_SIZE (1024u)
+  #define FSDEV_HAS_SBUF_ISO 0
 
 #elif CFG_TUSB_MCU == OPT_MCU_STM32G0
   #include "stm32g0xx.h"
   #define FSDEV_PMA_SIZE (2048u)
+  #define FSDEV_HAS_SBUF_ISO 1
   #define USB USB_DRD_FS
 
   #define USB_EP_CTR_RX USB_EP_VTRX
@@ -107,6 +115,7 @@
 #elif CFG_TUSB_MCU == OPT_MCU_STM32C0
   #include "stm32c0xx.h"
   #define FSDEV_PMA_SIZE (2048u)
+  #define FSDEV_HAS_SBUF_ISO 1
   #define USB USB_DRD_FS
   #define USB_EP_CTR_RX USB_CHEP_VTRX
   #define USB_EP_CTR_TX USB_CHEP_VTTX
@@ -121,6 +130,7 @@
 #elif CFG_TUSB_MCU == OPT_MCU_STM32H5
   #include "stm32h5xx.h"
   #define FSDEV_PMA_SIZE (2048u)
+  #define FSDEV_HAS_SBUF_ISO 1
   #define USB USB_DRD_FS
 
   #define USB_EP_CTR_RX USB_EP_VTRX
@@ -145,16 +155,19 @@
 #elif CFG_TUSB_MCU == OPT_MCU_STM32WB
   #include "stm32wbxx.h"
   #define FSDEV_PMA_SIZE (1024u)
+  #define FSDEV_HAS_SBUF_ISO 0
   /* ST provided header has incorrect value of USB_PMAADDR */
   #define FSDEV_PMA_BASE USB1_PMAADDR
 
 #elif CFG_TUSB_MCU == OPT_MCU_STM32L4
   #include "stm32l4xx.h"
   #define FSDEV_PMA_SIZE (1024u)
+  #define FSDEV_HAS_SBUF_ISO 0
 
 #elif CFG_TUSB_MCU == OPT_MCU_STM32L5
   #include "stm32l5xx.h"
   #define FSDEV_PMA_SIZE (1024u)
+  #define FSDEV_HAS_SBUF_ISO 0
 
   #ifndef USB_PMAADDR
     #define USB_PMAADDR (USB_BASE + (USB_PMAADDR_NS - USB_BASE_NS))
@@ -163,6 +176,7 @@
 #elif CFG_TUSB_MCU == OPT_MCU_STM32U5
   #include "stm32u5xx.h"
   #define FSDEV_PMA_SIZE (2048u)
+  #define FSDEV_HAS_SBUF_ISO 1
   #define USB USB_DRD_FS
 
   #define USB_EP_CTR_RX USB_EP_VTRX
@@ -187,6 +201,7 @@
 #elif CFG_TUSB_MCU == OPT_MCU_STM32U0
   #include "stm32u0xx.h"
   #define FSDEV_PMA_SIZE (2048u)
+  #define FSDEV_HAS_SBUF_ISO 1
   #define USB USB_DRD_FS
 
   #define USB_EP_CTR_RX USB_EP_VTRX
@@ -248,6 +263,29 @@
 #define USB_ISTR_ALL_EVENTS (USB_ISTR_PMAOVR | USB_ISTR_ERR | USB_ISTR_WKUP | USB_ISTR_SUSP | \
      USB_ISTR_RESET | USB_ISTR_SOF | USB_ISTR_ESOF | USB_ISTR_L1REQ_FORCED )
 
+#ifndef FSDEV_HAS_SBUF_ISO
+  #error "FSDEV_HAS_SBUF_ISO not defined"
+#endif
+
+#ifndef CFG_TUD_FSDEV_DOUBLE_BUFFERED_ISO_EP
+  // Defaults to double-buffered isochronous endpoints on devices with >1KB PMA
+  #if FSDEV_PMA_SIZE > 1024u
+    #define CFG_TUD_FSDEV_DOUBLE_BUFFERED_ISO_EP 1
+  #else
+    #define CFG_TUD_FSDEV_DOUBLE_BUFFERED_ISO_EP 0
+  #endif
+#endif
+
+#if FSDEV_HAS_SBUF_ISO != 0 && CFG_TUD_FSDEV_DOUBLE_BUFFERED_ISO_EP == 0
+  // If hardware has SBUF_ISO bit single-buffered endpoints consume only
+  // one half of endpoint pair register.
+  #define FSDEV_USE_SBUF_ISO 1
+#else
+  // Otherwise it consumes entire endpoint pair but we can at least save
+  // memory by configuring the same buffer twice.
+  #define FSDEV_USE_SBUF_ISO 0
+#endif
+
 //--------------------------------------------------------------------+
 //
 //--------------------------------------------------------------------+