mec lpc: address code style issues, plus fix string readmem

Author: DHowett

util/comm-mec_lpc.c

@@ -15,26 +15,30 @@
 
 #include "comm-host.h"
 
+/* from comm-lpc.c */
 int wait_for_ec(int status_addr, int timeout_usec);
 
-#define INITIAL_UDELAY 5     /* 5 us */
-#define MAXIMUM_UDELAY 10000 /* 10 ms */
-
 typedef enum _ec_xfer_direction { EC_MEC_WRITE, EC_MEC_READ } ec_xfer_direction;
 
-// As defined in MEC172x section 16.8.3
-// https://ww1.microchip.com/downloads/en/DeviceDoc/MEC172x-Data-Sheet-DS00003583C.pdf
+/* As defined in MEC172x section 16.8.3
+ * https://ww1.microchip.com/downloads/en/DeviceDoc/MEC172x-Data-Sheet-DS00003583C.pdf
+ */
 #define MEC_EC_BYTE_ACCESS               0x00
 #define MEC_EC_LONG_ACCESS_AUTOINCREMENT 0x03
 
 #define MEC_EC_ADDRESS_REGISTER0      0x0802
 #define MEC_EC_ADDRESS_REGISTER1      0x0803
 #define MEC_EC_DATA_REGISTER0         0x0804
 #define MEC_EC_DATA_REGISTER2         0x0806
+#define MEC_EC_MEMMAP_START            0x100
 
 static int ec_mec_xfer(ec_xfer_direction direction, uint16_t address,
 		       char *data, uint16_t size)
 {
+	/*
+	 * There's a cleverer way to do this, but it's somewhat less clear what's happening.
+	 * I prefer clarity over cleverness. :)
+	 */
 	int pos = 0;
 	uint16_t temp[2];
 	if (address % 4 > 0) {
@@ -47,13 +51,11 @@ static int ec_mec_xfer(ec_xfer_direction direction, uint16_t address,
 			else if (direction == EC_MEC_READ)
 				*storage = inb(MEC_EC_DATA_REGISTER0 + i);
 		}
-		address = (address + 4) & 0xFFFC; // Up to next multiple of 4
+		address = (address + 4) & 0xFFFC;
 	}
 
 	if (size - pos >= 4) {
 		outw((address & 0xFFFC) | MEC_EC_LONG_ACCESS_AUTOINCREMENT, MEC_EC_ADDRESS_REGISTER0);
-		// Chunk writing for anything large, 4 bytes at a time
-		// Writing to 804, 806 automatically increments dest address
 		while (size - pos >= 4) {
 			if (direction == EC_MEC_WRITE) {
 				memcpy(temp, &data[pos], sizeof(temp));
@@ -71,7 +73,6 @@ static int ec_mec_xfer(ec_xfer_direction direction, uint16_t address,
 	}
 
 	if (size - pos > 0) {
-		// Unaligned remaining data - R/W it by byte
 		outw((address & 0xFFFC) | MEC_EC_BYTE_ACCESS, MEC_EC_ADDRESS_REGISTER0);
 		for (int i = 0; i < (size - pos); ++i) {
 			char *storage = &data[pos + i];
@@ -180,8 +181,27 @@ static int ec_command_lpc_mec_3(int command, int version, const void *outdata,
 
 static int ec_readmem_lpc_mec(int offset, int bytes, void *dest)
 {
-	ec_mec_xfer(EC_MEC_READ, (EC_LPC_ADDR_MEMMAP - EC_HOST_CMD_REGION0) | (offset & 0x7FFF), dest, bytes);
-	return bytes;
+	int xfer_offset = MEC_EC_MEMMAP_START + offset;
+	int cnt = 0;
+	char* s = dest;
+
+	if (offset >= EC_MEMMAP_SIZE - bytes)
+		return -1;
+
+	if (bytes) {
+		ec_mec_xfer(EC_MEC_READ, xfer_offset, dest, bytes);
+		cnt = bytes;
+	} else {
+		/* Somewhat brute-force to set up a bunch of
+		 * individual transfers, but clearer than copying the xfer code
+		 * to add a stop condition.
+		 */
+		do {
+			ec_mec_xfer(EC_MEC_READ, xfer_offset++, s++, 1);
+			cnt++;
+		} while(*s != '\0' && xfer_offset < EC_MEMMAP_SIZE);
+	}
+	return cnt;
 }
 
 int comm_init_lpc_mec(void)