[PATCH v3 14/30] mfd: cros_ec: Add EC transport protocol v4

Gwendal Grignou
2019-05-09T21:14:30Z

Introduce a new transport procotol between EC and host.

Acked-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Acked-by: Benson Leung <bleung@chromium.org>
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
---
include/linux/mfd/cros_ec_commands.h | 143 ++++++++++++++++++++++++++-
1 file changed, 141 insertions(+), 2 deletions(-)

diff --git a/include/linux/mfd/cros_ec_commands.h b/include/linux/mfd/cros_ec_commands.h
index 76943e64998a..40a8069a58e8 100644
--- a/include/linux/mfd/cros_ec_commands.h
+++ b/include/linux/mfd/cros_ec_commands.h
@@ -455,7 +455,10 @@
#define EC_LPC_STATUS_BUSY_MASK \
(EC_LPC_STATUS_FROM_HOST | EC_LPC_STATUS_PROCESSING)

-/* Host command response codes */
+/*
+ * Host command response codes (16-bit). Note that response codes should be
+ * stored in a uint16_t rather than directly in a value of this type.
+ */
enum ec_status {
EC_RES_SUCCESS = 0,
EC_RES_INVALID_COMMAND = 1,
@@ -471,7 +474,13 @@ enum ec_status {
EC_RES_OVERFLOW = 11, /* Table / data overflow */
EC_RES_INVALID_HEADER = 12, /* Header contains invalid data */
EC_RES_REQUEST_TRUNCATED = 13, /* Didn't get the entire request */
- EC_RES_RESPONSE_TOO_BIG = 14 /* Response was too big to handle */
+ EC_RES_RESPONSE_TOO_BIG = 14, /* Response was too big to handle */
+ EC_RES_BUS_ERROR = 15, /* Communications bus error */
+ EC_RES_BUSY = 16, /* Up but too busy. Should retry */
+ EC_RES_INVALID_HEADER_VERSION = 17, /* Header version invalid */
+ EC_RES_INVALID_HEADER_CRC = 18, /* Header CRC invalid */
+ EC_RES_INVALID_DATA_CRC = 19, /* Data CRC invalid */
+ EC_RES_DUP_UNAVAILABLE = 20, /* Can't resend response */
};

/*
@@ -744,6 +753,136 @@ struct ec_host_response {
uint16_t reserved;
} __ec_align4;

+/*****************************************************************************/
+
+/*
+ * Host command protocol V4.
+ *
+ * Packets always start with a request or response header. They are followed
+ * by data_len bytes of data. If the data_crc_present flag is set, the data
+ * bytes are followed by a CRC-8 of that data, using using x^8 + x^2 + x + 1
+ * polynomial.
+ *
+ * Host algorithm when sending a request q:
+ *
+ * 101) tries_left=(some value, e.g. 3);
+ * 102) q.seq_num++
+ * 103) q.seq_dup=0
+ * 104) Calculate q.header_crc.
+ * 105) Send request q to EC.
+ * 106) Wait for response r. Go to 201 if received or 301 if timeout.
+ *
+ * 201) If r.struct_version != 4, go to 301.
+ * 202) If r.header_crc mismatches calculated CRC for r header, go to 301.
+ * 203) If r.data_crc_present and r.data_crc mismatches, go to 301.
+ * 204) If r.seq_num != q.seq_num, go to 301.
+ * 205) If r.seq_dup == q.seq_dup, return success.
+ * 207) If r.seq_dup == 1, go to 301.
+ * 208) Return error.
+ *
+ * 301) If --tries_left <= 0, return error.
+ * 302) If q.seq_dup == 1, go to 105.
+ * 303) q.seq_dup = 1
+ * 304) Go to 104.
+ *
+ * EC algorithm when receiving a request q.
+ * EC has response buffer r, error buffer e.
+ *
+ * 101) If q.struct_version != 4, set e.result = EC_RES_INVALID_HEADER_VERSION
+ * and go to 301
+ * 102) If q.header_crc mismatches calculated CRC, set e.result =
+ * EC_RES_INVALID_HEADER_CRC and go to 301
+ * 103) If q.data_crc_present, calculate data CRC. If that mismatches the CRC
+ * byte at the end of the packet, set e.result = EC_RES_INVALID_DATA_CRC
+ * and go to 301.
+ * 104) If q.seq_dup == 0, go to 201.
+ * 105) If q.seq_num != r.seq_num, go to 201.
+ * 106) If q.seq_dup == r.seq_dup, go to 205, else go to 203.
+ *
+ * 201) Process request q into response r.
+ * 202) r.seq_num = q.seq_num
+ * 203) r.seq_dup = q.seq_dup
+ * 204) Calculate r.header_crc
+ * 205) If r.data_len > 0 and data is no longer available, set e.result =
+ * EC_RES_DUP_UNAVAILABLE and go to 301.
+ * 206) Send response r.
+ *
+ * 301) e.seq_num = q.seq_num
+ * 302) e.seq_dup = q.seq_dup
+ * 303) Calculate e.header_crc.
+ * 304) Send error response e.
+ */
+
+/* Version 4 request from host */
+struct ec_host_request4 {
+ /*
+ * bits 0-3: struct_version: Structure version (=4)
+ * bit 4: is_response: Is response (=0)
+ * bits 5-6: seq_num: Sequence number
+ * bit 7: seq_dup: Sequence duplicate flag
+ */
+ uint8_t fields0;
+
+ /*
+ * bits 0-4: command_version: Command version
+ * bits 5-6: Reserved (set 0, ignore on read)
+ * bit 7: data_crc_present: Is data CRC present after data
+ */
+ uint8_t fields1;
+
+ /* Command code (EC_CMD_*) */
+ uint16_t command;
+
+ /* Length of data which follows this header (not including data CRC) */
+ uint16_t data_len;
+
+ /* Reserved (set 0, ignore on read) */
+ uint8_t reserved;
+
+ /* CRC-8 of above fields, using x^8 + x^2 + x + 1 polynomial */
+ uint8_t header_crc;
+} __ec_align4;
+
+/* Version 4 response from EC */
+struct ec_host_response4 {
+ /*
+ * bits 0-3: struct_version: Structure version (=4)
+ * bit 4: is_response: Is response (=1)
+ * bits 5-6: seq_num: Sequence number
+ * bit 7: seq_dup: Sequence duplicate flag
+ */
+ uint8_t fields0;
+
+ /*
+ * bits 0-6: Reserved (set 0, ignore on read)
+ * bit 7: data_crc_present: Is data CRC present after data
+ */
+ uint8_t fields1;
+
+ /* Result code (EC_RES_*) */
+ uint16_t result;
+
+ /* Length of data which follows this header (not including data CRC) */
+ uint16_t data_len;
+
+ /* Reserved (set 0, ignore on read) */
+ uint8_t reserved;
+
+ /* CRC-8 of above fields, using x^8 + x^2 + x + 1 polynomial */
+ uint8_t header_crc;
+} __ec_align4;
+
+/* Fields in fields0 byte */
+#define EC_PACKET4_0_STRUCT_VERSION_MASK 0x0f
+#define EC_PACKET4_0_IS_RESPONSE_MASK 0x10
+#define EC_PACKET4_0_SEQ_NUM_SHIFT 5
+#define EC_PACKET4_0_SEQ_NUM_MASK 0x60
+#define EC_PACKET4_0_SEQ_DUP_MASK 0x80
+
+/* Fields in fields1 byte */
+#define EC_PACKET4_1_COMMAND_VERSION_MASK 0x1f /* (request only) */
+#define EC_PACKET4_1_DATA_CRC_PRESENT_MASK 0x80
+
/*****************************************************************************/
/*
* Notes on commands:
--
2.21.0.1020.gf2820cf01a-goog