fw: Change max frame size to 128 bytes

doc/framing_protocol/framing_protocol.md

@@ -125,12 +125,12 @@ The bits in the command header byte should be interpreted as:
 0. 1 byte
 1. 4 bytes
 2. 32 bytes
-3. 512 bytes
+3. 128 bytes
 
 Note that the number of bytes indicated by the command data length field
 does **not** include the command header byte. This means that a complete
-command frame, with a header indicating a data length of 512 bytes, is
-512+1 bytes in length.
+command frame, with a header indicating a data length of 128 bytes, is
+128+1 bytes in length.
 
 Note that the host sets the frame ID tag. The ID tag in a given command
 MUST be preserved in the corresponding response to the command.
@@ -148,7 +148,7 @@ Some examples to clarify endpoints and commands:
   data. The single byte could indicate action such as reading from the
   TRNG or resetting the application_fpga.
 
-* 0x13: A command to the FW in the application_fpga with 512 bytes of
+* 0x13: A command to the FW in the application_fpga with 128 bytes of
   data. The data could for example be parts of an application binary to
   be loaded into the program memory.
 
@@ -179,13 +179,13 @@ The bits in the response header byte should be interpreted as:
 0. 1 byte
 1. 4 bytes
 2. 32 bytes
-3. 512 bytes
+3. 128 bytes
 
 
 Note that the number of bytes indicated by the response data length field
 does **not** include the response header byte. This means that a complete
-response frame, with a header indicating a data length of 512 bytes, is
-512+1 bytes in length.
+response frame, with a header indicating a data length of 128 bytes, is
+128+1 bytes in length.
 
 Note that the ID in a response MUST be the same ID as was present in the
 header of the command being responded to.
@@ -205,7 +205,7 @@ less available for the "payload" of the response.
   responds with a single byte of data.
 
 * 0x1b: A successful command to the application running in the
-  application_fpga. The response contains 512 bytes of data, for example
+  application_fpga. The response contains 128 bytes of data, for example
   an EdDSA Ed25519 signature.
 
 

doc/system_description/software.md

@@ -308,10 +308,10 @@ Response to `FW_CMD_LOAD_APP`
 
 | *name* | *size (bytes)* | *comment*           |
 |--------|----------------|---------------------|
-| data   | 511            | Raw binary app data |
+| data   | 127            | Raw binary app data |
 
-Load 511 bytes of raw app binary into device RAM. Should be sent
-consecutively over the complete raw binary. (512 == largest frame
+Load 127 bytes of raw app binary into device RAM. Should be sent
+consecutively over the complete raw binary. (128 == largest frame
 length minus the command byte).
 
 #### `FW_RSP_LOAD_APP_DATA` (0x06)
@@ -377,9 +377,9 @@ host <-
 
 ```
 host ->
-  u8 CMD[1 + 512];
+  u8 CMD[1 + 128];
 
-  CMD[0].len = 512  // command frame format
+  CMD[0].len = 128  // command frame format
   CMD[1]     = 0x03 // FW_CMD_LOAD_APP
 
   CMD[2..6]  = APP_SIZE
@@ -398,11 +398,11 @@ host <-
 
   RSP[3..]   = 0
 
-repeat ceil(APP_SIZE / 511) times:
+repeat ceil(APP_SIZE / 127) times:
 host ->
-  u8 CMD[1 + 512];
+  u8 CMD[1 + 128];
 
-  CMD[0].len = 512  // command frame format
+  CMD[0].len = 128  // command frame format
   CMD[1]     = 0x05 // FW_CMD_LOAD_APP_DATA
 
   CMD[2..]   = APP_DATA (511 bytes of app data, pad with zeros)
@@ -422,9 +422,9 @@ Except response from last chunk of app data which is:
 
 ```
 host <-
-  u8 RSP[1 + 512]
+  u8 RSP[1 + 128]
 
-  RSP[0].len = 512  // command frame format
+  RSP[0].len = 128  // command frame format
   RSP[1]     = 0x07 // FW_RSP_LOAD_APP_DATA_READY
 
   RSP[2]     = STATUS

hw/application_fpga/fw/tk1/main.c

@@ -188,7 +188,7 @@ static enum state initial_commands(const struct frame_header *hdr,
 		uint32_t local_app_size;
 
 		htif_puts("cmd: load-app(size, uss)\n");
-		if (hdr->len != 512) {
+		if (hdr->len != 128) {
 			// Bad length
 			state = FW_STATE_FAIL;
 			break;
@@ -253,14 +253,14 @@ static enum state loading_commands(const struct frame_header *hdr,
 	switch (cmd[0]) {
 	case FW_CMD_LOAD_APP_DATA:
 		htif_puts("cmd: load-app-data\n");
-		if (hdr->len != 512) {
+		if (hdr->len != 128) {
 			// Bad length
 			state = FW_STATE_FAIL;
 			break;
 		}
 
-		if (ctx->left > (512 - 1)) {
-			nbytes = 512 - 1;
+		if (ctx->left > (128 - 1)) {
+			nbytes = 128 - 1;
 		} else {
 			nbytes = ctx->left;
 		}

hw/application_fpga/fw/tk1/proto.c

@@ -5,6 +5,7 @@
 
 #include "proto.h"
 #include "../tk1_mem.h"
+#include "assert.h"
 #include "led.h"
 #include "lib.h"
 #include "state.h"
@@ -22,6 +23,7 @@ static uint8_t genhdr(uint8_t id, uint8_t endpoint, uint8_t status,
 static int parseframe(uint8_t b, struct frame_header *hdr);
 static void write(uint8_t *buf, size_t nbytes);
 static int read(uint8_t *buf, size_t bufsize, size_t nbytes);
+static int bytelen(enum cmdlen cmdlen);
 
 static uint8_t genhdr(uint8_t id, uint8_t endpoint, uint8_t status,
 		      enum cmdlen len)
@@ -71,25 +73,7 @@ static int parseframe(uint8_t b, struct frame_header *hdr)
 
 	hdr->id = (b & 0x60) >> 5;
 	hdr->endpoint = (b & 0x18) >> 3;
-
-	// Length
-	switch (b & 0x3) {
-	case LEN_1:
-		hdr->len = 1;
-		break;
-	case LEN_4:
-		hdr->len = 4;
-		break;
-	case LEN_32:
-		hdr->len = 32;
-		break;
-	case LEN_512:
-		hdr->len = 512;
-		break;
-	default:
-		// Unknown length
-		return -1;
-	}
+	hdr->len = bytelen(b & 0x3);
 
 	return 0;
 }
@@ -104,27 +88,22 @@ void fwreply(struct frame_header hdr, enum fwcmd rspcode, uint8_t *buf)
 	switch (rspcode) {
 	case FW_RSP_NAME_VERSION:
 		len = LEN_32;
-		nbytes = 32;
 		break;
 
 	case FW_RSP_LOAD_APP:
 		len = LEN_4;
-		nbytes = 4;
 		break;
 
 	case FW_RSP_LOAD_APP_DATA:
 		len = LEN_4;
-		nbytes = 4;
 		break;
 
 	case FW_RSP_LOAD_APP_DATA_READY:
-		len = LEN_512;
-		nbytes = 512;
+		len = LEN_128;
 		break;
 
 	case FW_RSP_GET_UDI:
 		len = LEN_32;
-		nbytes = 32;
 		break;
 
 	default:
@@ -134,6 +113,8 @@ void fwreply(struct frame_header hdr, enum fwcmd rspcode, uint8_t *buf)
 		return;
 	}
 
+	nbytes = bytelen(len);
+
 	// Frame Protocol Header
 	writebyte(genhdr(hdr.id, hdr.endpoint, 0x0, len));
 
@@ -182,3 +163,33 @@ static int read(uint8_t *buf, size_t bufsize, size_t nbytes)
 
 	return 0;
 }
+
+// bytelen returns the number of bytes a cmdlen takes
+static int bytelen(enum cmdlen cmdlen)
+{
+	int len;
+
+	switch (cmdlen) {
+	case LEN_1:
+		len = 1;
+		break;
+
+	case LEN_4:
+		len = 4;
+		break;
+
+	case LEN_32:
+		len = 32;
+		break;
+
+	case LEN_128:
+		len = 128;
+		break;
+
+	default:
+		// Shouldn't happen
+		assert(1 == 2);
+	}
+
+	return len;
+}

hw/application_fpga/fw/tk1/proto.h

@@ -19,10 +19,10 @@ enum cmdlen {
 	LEN_1,
 	LEN_4,
 	LEN_32,
-	LEN_512
+	LEN_128
 };
 
-#define CMDLEN_MAXBYTES 512
+#define CMDLEN_MAXBYTES 128
 
 // clang-format off
 enum fwcmd {