platform/chrome: cros_ec_lpc: MEC access can return error code

cros_ec_lpc_io_bytes_mec was returning a u8 checksum of all bytes
read/written, which didn't leave room to indicate errors. Change this
u8 to an int where negative values indicate an error, and non-negative
values are the checksum as before.
Tested-by: Dustin L. Howett <dustin@howett.net>
Signed-off-by: Ben Walsh <ben@jubnut.com>
Link: https://lore.kernel.org/r/20240605063351.14836-2-ben@jubnut.comSigned-off-by: Tzung-Bi Shih <tzungbi@kernel.org>

drivers/platform/chrome/cros_ec_lpc.c

@@ -62,14 +62,16 @@ struct cros_ec_lpc {
 
 /**
  * struct lpc_driver_ops - LPC driver operations
- * @read: Copy length bytes from EC address offset into buffer dest. Returns
- *        the 8-bit checksum of all bytes read.
- * @write: Copy length bytes from buffer msg into EC address offset. Returns
- *         the 8-bit checksum of all bytes written.
+ * @read: Copy length bytes from EC address offset into buffer dest.
+ *        Returns a negative error code on error, or the 8-bit checksum
+ *        of all bytes read.
+ * @write: Copy length bytes from buffer msg into EC address offset.
+ *         Returns a negative error code on error, or the 8-bit checksum
+ *         of all bytes written.
  */
 struct lpc_driver_ops {
-	u8 (*read)(unsigned int offset, unsigned int length, u8 *dest);
-	u8 (*write)(unsigned int offset, unsigned int length, const u8 *msg);
+	int (*read)(unsigned int offset, unsigned int length, u8 *dest);
+	int (*write)(unsigned int offset, unsigned int length, const u8 *msg);
 };
 
 static struct lpc_driver_ops cros_ec_lpc_ops = { };
@@ -78,10 +80,10 @@ static struct lpc_driver_ops cros_ec_lpc_ops = { };
  * A generic instance of the read function of struct lpc_driver_ops, used for
  * the LPC EC.
  */
-static u8 cros_ec_lpc_read_bytes(unsigned int offset, unsigned int length,
+static int cros_ec_lpc_read_bytes(unsigned int offset, unsigned int length,
 				  u8 *dest)
 {
-	int sum = 0;
+	u8 sum = 0;
 	int i;
 
 	for (i = 0; i < length; ++i) {
@@ -97,10 +99,10 @@ static u8 cros_ec_lpc_read_bytes(unsigned int offset, unsigned int length,
  * A generic instance of the write function of struct lpc_driver_ops, used for
  * the LPC EC.
  */
-static u8 cros_ec_lpc_write_bytes(unsigned int offset, unsigned int length,
+static int cros_ec_lpc_write_bytes(unsigned int offset, unsigned int length,
 				   const u8 *msg)
 {
-	int sum = 0;
+	u8 sum = 0;
 	int i;
 
 	for (i = 0; i < length; ++i) {
@@ -116,7 +118,7 @@ static u8 cros_ec_lpc_write_bytes(unsigned int offset, unsigned int length,
  * An instance of the read function of struct lpc_driver_ops, used for the
  * MEC variant of LPC EC.
  */
-static u8 cros_ec_lpc_mec_read_bytes(unsigned int offset, unsigned int length,
+static int cros_ec_lpc_mec_read_bytes(unsigned int offset, unsigned int length,
 				      u8 *dest)
 {
 	int in_range = cros_ec_lpc_mec_in_range(offset, length);
@@ -135,7 +137,7 @@ static u8 cros_ec_lpc_mec_read_bytes(unsigned int offset, unsigned int length,
  * An instance of the write function of struct lpc_driver_ops, used for the
  * MEC variant of LPC EC.
  */
-static u8 cros_ec_lpc_mec_write_bytes(unsigned int offset, unsigned int length,
+static int cros_ec_lpc_mec_write_bytes(unsigned int offset, unsigned int length,
 				       const u8 *msg)
 {
 	int in_range = cros_ec_lpc_mec_in_range(offset, length);
@@ -154,11 +156,14 @@ static int ec_response_timed_out(void)
 {
 	unsigned long one_second = jiffies + HZ;
 	u8 data;
+	int ret;
 
 	usleep_range(200, 300);
 	do {
-		if (!(cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_CMD, 1, &data) &
-		    EC_LPC_STATUS_BUSY_MASK))
+		ret = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_CMD, 1, &data);
+		if (ret < 0)
+			return ret;
+		if (!(data & EC_LPC_STATUS_BUSY_MASK))
 			return 0;
 		usleep_range(100, 200);
 	} while (time_before(jiffies, one_second));
@@ -179,28 +184,41 @@ static int cros_ec_pkt_xfer_lpc(struct cros_ec_device *ec,
 		goto done;
 
 	/* Write buffer */
-	cros_ec_lpc_ops.write(EC_LPC_ADDR_HOST_PACKET, ret, ec->dout);
+	ret = cros_ec_lpc_ops.write(EC_LPC_ADDR_HOST_PACKET, ret, ec->dout);
+	if (ret < 0)
+		goto done;
 
 	/* Here we go */
 	sum = EC_COMMAND_PROTOCOL_3;
-	cros_ec_lpc_ops.write(EC_LPC_ADDR_HOST_CMD, 1, &sum);
+	ret = cros_ec_lpc_ops.write(EC_LPC_ADDR_HOST_CMD, 1, &sum);
+	if (ret < 0)
+		goto done;
 
-	if (ec_response_timed_out()) {
+	ret = ec_response_timed_out();
+	if (ret < 0)
+		goto done;
+	if (ret) {
 		dev_warn(ec->dev, "EC response timed out\n");
 		ret = -EIO;
 		goto done;
 	}
 
 	/* Check result */
-	msg->result = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_DATA, 1, &sum);
+	ret = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_DATA, 1, &sum);
+	if (ret < 0)
+		goto done;
+	msg->result = ret;
 	ret = cros_ec_check_result(ec, msg);
 	if (ret)
 		goto done;
 
 	/* Read back response */
 	dout = (u8 *)&response;
-	sum = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_PACKET, sizeof(response),
+	ret = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_PACKET, sizeof(response),
 				   dout);
+	if (ret < 0)
+		goto done;
+	sum = ret;
 
 	msg->result = response.result;
 
@@ -213,9 +231,12 @@ static int cros_ec_pkt_xfer_lpc(struct cros_ec_device *ec,
 	}
 
 	/* Read response and process checksum */
-	sum += cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_PACKET +
+	ret = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_PACKET +
 				   sizeof(response), response.data_len,
 				   msg->data);
+	if (ret < 0)
+		goto done;
+	sum += ret;
 
 	if (sum) {
 		dev_err(ec->dev,
@@ -255,32 +276,47 @@ static int cros_ec_cmd_xfer_lpc(struct cros_ec_device *ec,
 	sum = msg->command + args.flags + args.command_version + args.data_size;
 
 	/* Copy data and update checksum */
-	sum += cros_ec_lpc_ops.write(EC_LPC_ADDR_HOST_PARAM, msg->outsize,
+	ret = cros_ec_lpc_ops.write(EC_LPC_ADDR_HOST_PARAM, msg->outsize,
 				    msg->data);
+	if (ret < 0)
+		goto done;
+	sum += ret;
 
 	/* Finalize checksum and write args */
 	args.checksum = sum;
-	cros_ec_lpc_ops.write(EC_LPC_ADDR_HOST_ARGS, sizeof(args),
+	ret = cros_ec_lpc_ops.write(EC_LPC_ADDR_HOST_ARGS, sizeof(args),
 				    (u8 *)&args);
+	if (ret < 0)
+		goto done;
 
 	/* Here we go */
 	sum = msg->command;
-	cros_ec_lpc_ops.write(EC_LPC_ADDR_HOST_CMD, 1, &sum);
+	ret = cros_ec_lpc_ops.write(EC_LPC_ADDR_HOST_CMD, 1, &sum);
+	if (ret < 0)
+		goto done;
 
-	if (ec_response_timed_out()) {
+	ret = ec_response_timed_out();
+	if (ret < 0)
+		goto done;
+	if (ret) {
 		dev_warn(ec->dev, "EC response timed out\n");
 		ret = -EIO;
 		goto done;
 	}
 
 	/* Check result */
-	msg->result = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_DATA, 1, &sum);
+	ret = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_DATA, 1, &sum);
+	if (ret < 0)
+		goto done;
+	msg->result = ret;
 	ret = cros_ec_check_result(ec, msg);
 	if (ret)
 		goto done;
 
 	/* Read back args */
-	cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_ARGS, sizeof(args), (u8 *)&args);
+	ret = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_ARGS, sizeof(args), (u8 *)&args);
+	if (ret < 0)
+		goto done;
 
 	if (args.data_size > msg->insize) {
 		dev_err(ec->dev,
@@ -294,8 +330,11 @@ static int cros_ec_cmd_xfer_lpc(struct cros_ec_device *ec,
 	sum = msg->command + args.flags + args.command_version + args.data_size;
 
 	/* Read response and update checksum */
-	sum += cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_PARAM, args.data_size,
+	ret = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_PARAM, args.data_size,
 				   msg->data);
+	if (ret < 0)
+		goto done;
+	sum += ret;
 
 	/* Verify checksum */
 	if (args.checksum != sum) {
@@ -320,19 +359,24 @@ static int cros_ec_lpc_readmem(struct cros_ec_device *ec, unsigned int offset,
 	int i = offset;
 	char *s = dest;
 	int cnt = 0;
+	int ret;
 
 	if (offset >= EC_MEMMAP_SIZE - bytes)
 		return -EINVAL;
 
 	/* fixed length */
 	if (bytes) {
-		cros_ec_lpc_ops.read(ec_lpc->mmio_memory_base + offset, bytes, s);
+		ret = cros_ec_lpc_ops.read(ec_lpc->mmio_memory_base + offset, bytes, s);
+		if (ret < 0)
+			return ret;
 		return bytes;
 	}
 
 	/* string */
 	for (; i < EC_MEMMAP_SIZE; i++, s++) {
-		cros_ec_lpc_ops.read(ec_lpc->mmio_memory_base + i, 1, s);
+		ret = cros_ec_lpc_ops.read(ec_lpc->mmio_memory_base + i, 1, s);
+		if (ret < 0)
+			return ret;
 		cnt++;
 		if (!*s)
 			break;
@@ -425,7 +469,9 @@ static int cros_ec_lpc_probe(struct platform_device *pdev)
 	 */
 	cros_ec_lpc_ops.read = cros_ec_lpc_mec_read_bytes;
 	cros_ec_lpc_ops.write = cros_ec_lpc_mec_write_bytes;
-	cros_ec_lpc_ops.read(EC_LPC_ADDR_MEMMAP + EC_MEMMAP_ID, 2, buf);
+	ret = cros_ec_lpc_ops.read(EC_LPC_ADDR_MEMMAP + EC_MEMMAP_ID, 2, buf);
+	if (ret < 0)
+		return ret;
 	if (buf[0] != 'E' || buf[1] != 'C') {
 		if (!devm_request_region(dev, ec_lpc->mmio_memory_base, EC_MEMMAP_SIZE,
 					 dev_name(dev))) {
@@ -436,8 +482,10 @@ static int cros_ec_lpc_probe(struct platform_device *pdev)
 		/* Re-assign read/write operations for the non MEC variant */
 		cros_ec_lpc_ops.read = cros_ec_lpc_read_bytes;
 		cros_ec_lpc_ops.write = cros_ec_lpc_write_bytes;
-		cros_ec_lpc_ops.read(ec_lpc->mmio_memory_base + EC_MEMMAP_ID, 2,
+		ret = cros_ec_lpc_ops.read(ec_lpc->mmio_memory_base + EC_MEMMAP_ID, 2,
 					   buf);
+		if (ret < 0)
+			return ret;
 		if (buf[0] != 'E' || buf[1] != 'C') {
 			dev_err(dev, "EC ID not detected\n");
 			return -ENODEV;

drivers/platform/chrome/cros_ec_lpc_mec.c

@@ -67,9 +67,10 @@ int cros_ec_lpc_mec_in_range(unsigned int offset, unsigned int length)
  * @length:  Number of bytes to read / write
  * @buf:     Destination / source buffer
  *
- * Return: 8-bit checksum of all bytes read / written
+ * @return:  A negative error code on error, or 8-bit checksum of all
+ *           bytes read / written
  */
-u8 cros_ec_lpc_io_bytes_mec(enum cros_ec_lpc_mec_io_type io_type,
+int cros_ec_lpc_io_bytes_mec(enum cros_ec_lpc_mec_io_type io_type,
 			     unsigned int offset, unsigned int length,
 			     u8 *buf)
 {

drivers/platform/chrome/cros_ec_lpc_mec.h

@@ -64,9 +64,10 @@ int cros_ec_lpc_mec_in_range(unsigned int offset, unsigned int length);
  * @length:  Number of bytes to read / write
  * @buf:     Destination / source buffer
  *
- * @return 8-bit checksum of all bytes read / written
+ * @return:  A negative error code on error, or 8-bit checksum of all
+ *           bytes read / written
  */
-u8 cros_ec_lpc_io_bytes_mec(enum cros_ec_lpc_mec_io_type io_type,
+int cros_ec_lpc_io_bytes_mec(enum cros_ec_lpc_mec_io_type io_type,
 			     unsigned int offset, unsigned int length, u8 *buf);
 
 #endif /* __CROS_EC_LPC_MEC_H */

drivers/platform/chrome/wilco_ec/mailbox.c

@@ -117,13 +117,17 @@ static int wilco_ec_transfer(struct wilco_ec_device *ec,
 			     struct wilco_ec_request *rq)
 {
 	struct wilco_ec_response *rs;
-	u8 checksum;
+	int ret;
 	u8 flag;
 
 	/* Write request header, then data */
-	cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE, 0, sizeof(*rq), (u8 *)rq);
-	cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE, sizeof(*rq), msg->request_size,
+	ret = cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE, 0, sizeof(*rq), (u8 *)rq);
+	if (ret < 0)
+		return ret;
+	ret = cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE, sizeof(*rq), msg->request_size,
 				       msg->request_data);
+	if (ret < 0)
+		return ret;
 
 	/* Start the command */
 	outb(EC_MAILBOX_START_COMMAND, ec->io_command->start);
@@ -149,10 +153,12 @@ static int wilco_ec_transfer(struct wilco_ec_device *ec,
 
 	/* Read back response */
 	rs = ec->data_buffer;
-	checksum = cros_ec_lpc_io_bytes_mec(MEC_IO_READ, 0,
+	ret = cros_ec_lpc_io_bytes_mec(MEC_IO_READ, 0,
 				       sizeof(*rs) + EC_MAILBOX_DATA_SIZE,
 				       (u8 *)rs);
-	if (checksum) {
+	if (ret < 0)
+		return ret;
+	if (ret) {
 		dev_dbg(ec->dev, "bad packet checksum 0x%02x\n", rs->checksum);
 		return -EBADMSG;
 	}