From cdd4177968c0539e88f3acce7a901a1b3a8a298b Mon Sep 17 00:00:00 2001
From: Philippe Teuwen <phil@teuwen.org>
Date: Mon, 22 Apr 2019 00:30:01 +0200
Subject: [PATCH] usart_writebuffer_sync simplified as we're always sending in
 blocking mode anyway

---
 armsrc/appmain.c |  6 +++---
 common/cmd.c     |  4 ++--
 common/usart.c   | 26 ++++++++------------------
 3 files changed, 13 insertions(+), 23 deletions(-)

diff --git a/armsrc/appmain.c b/armsrc/appmain.c
index aa85df22d..298f4df7f 100644
--- a/armsrc/appmain.c
+++ b/armsrc/appmain.c
@@ -1100,7 +1100,7 @@ static void PacketReceived(PacketCommandNG *packet) {
             strncat(at, s_at, sizeof(at) - strlen(at) - 1);
             DbpString("Try AT baud rate setting");
             usart_init();
-            int16_t res = usart_writebuffer((uint8_t*)&at, sizeof(at));
+            int16_t res = usart_writebuffer_sync((uint8_t*)&at, sizeof(at));
             WaitMS(1);
             Dbprintf("SEND %d | %c%c%c%c%c%c%c%c%c%c%c", res,  at[0], at[1], at[2], at[3], at[4], at[5], at[6], at[7], at[8], at[9], at[10]);
 
@@ -1122,7 +1122,7 @@ static void PacketReceived(PacketCommandNG *packet) {
             }
 
             static const char *welcome = "Proxmark3 Serial interface via FPC ready\r\n";
-            usart_writebuffer((uint8_t *)welcome, strlen(welcome));
+            usart_writebuffer_sync((uint8_t *)welcome, strlen(welcome));
 
             sprintf(dest, "| bytes 0x%02x 0x%02x 0x%02x 0x%02x\r\n"
                     , packet->data.asBytes[0]
@@ -1130,7 +1130,7 @@ static void PacketReceived(PacketCommandNG *packet) {
                     , packet->data.asBytes[2]
                     , packet->data.asBytes[3]
                    );
-            usart_writebuffer((uint8_t *)dest, strlen(dest));
+            usart_writebuffer_sync((uint8_t *)dest, strlen(dest));
 
 
             LED_A_ON();
diff --git a/common/cmd.c b/common/cmd.c
index fb8396051..13ca856d8 100644
--- a/common/cmd.c
+++ b/common/cmd.c
@@ -72,7 +72,7 @@ int16_t reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, voi
 
     if (reply_via_fpc) {
 #ifdef WITH_FPC_HOST
-        sendlen = usart_writebuffer((uint8_t *)&txcmd, sizeof(PacketResponseOLD));
+        sendlen = usart_writebuffer_sync((uint8_t *)&txcmd, sizeof(PacketResponseOLD));
 //        Dbprintf_usb("Sent %i bytes over usart", len);
 #else
         return PM3_EDEVNOTSUPP;
@@ -124,7 +124,7 @@ static int16_t reply_ng_internal(uint16_t cmd, int16_t status, uint8_t *data, si
 
     if (reply_via_fpc) {
 #ifdef WITH_FPC_HOST
-        sendlen = usart_writebuffer((uint8_t *)&txBufferNG, txBufferNGLen);
+        sendlen = usart_writebuffer_sync((uint8_t *)&txBufferNG, txBufferNGLen);
 //        Dbprintf_usb("Sent %i bytes over usart", len);
 #else
         return PM3_EDEVNOTSUPP;
diff --git a/common/usart.c b/common/usart.c
index 8d9b74257..cb4153062 100644
--- a/common/usart.c
+++ b/common/usart.c
@@ -129,25 +129,15 @@ uint32_t usart_read_ng(uint8_t *data, size_t len) {
 }
 
 // transfer from device to client
-inline int16_t usart_writebuffer(uint8_t *data, size_t len) {
+inline int16_t usart_writebuffer_sync(uint8_t *data, size_t len) {
 
-    // Wait for one free PDC bank
-    while (pUS1->US_TCR && pUS1->US_TNCR) {};
-
-    // Check if the current PDC bank is free
-    if (pUS1->US_TCR == 0) {
-        pUS1->US_TPR = (uint32_t)data;
-        pUS1->US_TCR = len;
-    }
-    // Check if the backup PDC bank is free
-    else if (pUS1->US_TNCR == 0) {
-        pUS1->US_TNPR = (uint32_t)data;
-        pUS1->US_TNCR = len;
-    } else {
-        // we shouldn't be here
-        return 0;
-    }
-    //wait until finishing all transfers
+    // Wait for current PDC bank to be free
+    // (and check next bank too, in case there will be a usart_writebuffer_async)
+    while (pUS1->US_TNCR || pUS1->US_TCR) {};
+    pUS1->US_TPR = (uint32_t)data;
+    pUS1->US_TCR = len;
+    // Wait until finishing all transfers to make sure "data" buffer can be discarded
+    // (if we don't wait here, bulk send as e.g. "hw status" will fail)
     while (pUS1->US_TNCR || pUS1->US_TCR) {};
     return len;
 }