platform/chrome: wilco_ec: Remove 256 byte transfers

The 0xF6 command, intended to send and receive 256 byte payloads to
and from the EC, is not needed. The 0xF5 command for 32 byte
payloads is sufficient. This patch removes support for the 0xF6
command and 256 byte payloads.

Signed-off-by: Nick Crews <ncrews@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>

Documentation/ABI/testing/debugfs-wilco-ec

@@ -23,11 +23,9 @@ Description:
 
 		For writing, bytes 0-1 indicate the message type, one of enum
 		wilco_ec_msg_type. Byte 2+ consist of the data passed in the
-		request, starting at MBOX[0]
-
-		At least three bytes are required for writing, two for the type
-		and at least a single byte of data. Only the first
-		EC_MAILBOX_DATA_SIZE bytes of MBOX will be used.
+		request, starting at MBOX[0]. At least three bytes are required
+		for writing, two for the type and at least a single byte of
+		data.
 
 		Example:
 		// Request EC info type 3 (EC firmware build date)
@@ -40,7 +38,7 @@ Description:
 		$ cat /sys/kernel/debug/wilco_ec/raw
 		00 00 31 32 2f 32 31 2f 31 38 00 38 00 01 00 2f 00  ..12/21/18.8...
 
-		Note that the first 32 bytes of the received MBOX[] will be
-		printed, even if some of the data is junk. It is up to you to
-		know how many of the first bytes of data are the actual
-		response.
+		Note that the first 16 bytes of the received MBOX[] will be
+		printed, even if some of the data is junk, and skipping bytes
+		17 to 32. It is up to you to know how many of the first bytes of
+		data are the actual response.

drivers/platform/chrome/wilco_ec/core.c

@@ -52,9 +52,7 @@ static int wilco_ec_probe(struct platform_device *pdev)
 	ec->dev = dev;
 	mutex_init(&ec->mailbox_lock);
 
-	/* Largest data buffer size requirement is extended data response */
-	ec->data_size = sizeof(struct wilco_ec_response) +
-		EC_MAILBOX_DATA_SIZE_EXTENDED;
+	ec->data_size = sizeof(struct wilco_ec_response) + EC_MAILBOX_DATA_SIZE;
 	ec->data_buffer = devm_kzalloc(dev, ec->data_size, GFP_KERNEL);
 	if (!ec->data_buffer)
 		return -ENOMEM;

drivers/platform/chrome/wilco_ec/debugfs.c

@@ -17,13 +17,13 @@
 #define DRV_NAME "wilco-ec-debugfs"
 
 /* The 256 raw bytes will take up more space when represented as a hex string */
-#define FORMATTED_BUFFER_SIZE (EC_MAILBOX_DATA_SIZE_EXTENDED * 4)
+#define FORMATTED_BUFFER_SIZE (EC_MAILBOX_DATA_SIZE * 4)
 
 struct wilco_ec_debugfs {
 	struct wilco_ec_device *ec;
 	struct dentry *dir;
 	size_t response_size;
-	u8 raw_data[EC_MAILBOX_DATA_SIZE_EXTENDED];
+	u8 raw_data[EC_MAILBOX_DATA_SIZE];
 	u8 formatted_data[FORMATTED_BUFFER_SIZE];
 };
 static struct wilco_ec_debugfs *debug_info;
@@ -124,12 +124,6 @@ static ssize_t raw_write(struct file *file, const char __user *user_buf,
 	msg.response_data = debug_info->raw_data;
 	msg.response_size = EC_MAILBOX_DATA_SIZE;
 
-	/* Telemetry commands use extended response data */
-	if (msg.type == WILCO_EC_MSG_TELEMETRY_LONG) {
-		msg.flags |= WILCO_EC_FLAG_EXTENDED_DATA;
-		msg.response_size = EC_MAILBOX_DATA_SIZE_EXTENDED;
-	}
-
 	ret = wilco_ec_mailbox(debug_info->ec, &msg);
 	if (ret < 0)
 		return ret;

drivers/platform/chrome/wilco_ec/mailbox.c

@@ -119,7 +119,6 @@ static int wilco_ec_transfer(struct wilco_ec_device *ec,
 	struct wilco_ec_response *rs;
 	u8 checksum;
 	u8 flag;
-	size_t size;
 
 	/* Write request header, then data */
 	cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE, 0, sizeof(*rq), (u8 *)rq);
@@ -148,21 +147,11 @@ static int wilco_ec_transfer(struct wilco_ec_device *ec,
 		return -EIO;
 	}
 
-	/*
-	 * The EC always returns either EC_MAILBOX_DATA_SIZE or
-	 * EC_MAILBOX_DATA_SIZE_EXTENDED bytes of data, so we need to
-	 * calculate the checksum on **all** of this data, even if we
-	 * won't use all of it.
-	 */
-	if (msg->flags & WILCO_EC_FLAG_EXTENDED_DATA)
-		size = EC_MAILBOX_DATA_SIZE_EXTENDED;
-	else
-		size = EC_MAILBOX_DATA_SIZE;
-
 	/* Read back response */
 	rs = ec->data_buffer;
 	checksum = cros_ec_lpc_io_bytes_mec(MEC_IO_READ, 0,
-					    sizeof(*rs) + size, (u8 *)rs);
+					    sizeof(*rs) + EC_MAILBOX_DATA_SIZE,
+					    (u8 *)rs);
 	if (checksum) {
 		dev_dbg(ec->dev, "bad packet checksum 0x%02x\n", rs->checksum);
 		return -EBADMSG;
@@ -173,9 +162,9 @@ static int wilco_ec_transfer(struct wilco_ec_device *ec,
 		return -EBADMSG;
 	}
 
-	if (rs->data_size != size) {
-		dev_dbg(ec->dev, "unexpected packet size (%u != %zu)",
-			rs->data_size, size);
+	if (rs->data_size != EC_MAILBOX_DATA_SIZE) {
+		dev_dbg(ec->dev, "unexpected packet size (%u != %u)",
+			rs->data_size, EC_MAILBOX_DATA_SIZE);
 		return -EMSGSIZE;
 	}
 

include/linux/platform_data/wilco-ec.h

@@ -13,12 +13,9 @@
 
 /* Message flags for using the mailbox() interface */
 #define WILCO_EC_FLAG_NO_RESPONSE	BIT(0) /* EC does not respond */
-#define WILCO_EC_FLAG_EXTENDED_DATA	BIT(1) /* EC returns 256 data bytes */
 
 /* Normal commands have a maximum 32 bytes of data */
 #define EC_MAILBOX_DATA_SIZE		32
-/* Extended commands have 256 bytes of response data */
-#define EC_MAILBOX_DATA_SIZE_EXTENDED	256
 
 /**
  * struct wilco_ec_device - Wilco Embedded Controller handle.
@@ -85,14 +82,12 @@ struct wilco_ec_response {
  * enum wilco_ec_msg_type - Message type to select a set of command codes.
  * @WILCO_EC_MSG_LEGACY: Legacy EC messages for standard EC behavior.
  * @WILCO_EC_MSG_PROPERTY: Get/Set/Sync EC controlled NVRAM property.
- * @WILCO_EC_MSG_TELEMETRY_SHORT: 32 bytes of telemetry data provided by the EC.
- * @WILCO_EC_MSG_TELEMETRY_LONG: 256 bytes of telemetry data provided by the EC.
+ * @WILCO_EC_MSG_TELEMETRY: Request telemetry data from the EC.
  */
 enum wilco_ec_msg_type {
 	WILCO_EC_MSG_LEGACY = 0x00f0,
 	WILCO_EC_MSG_PROPERTY = 0x00f2,
-	WILCO_EC_MSG_TELEMETRY_SHORT = 0x00f5,
-	WILCO_EC_MSG_TELEMETRY_LONG = 0x00f6,
+	WILCO_EC_MSG_TELEMETRY = 0x00f5,
 };
 
 /**