i2c: Split i2c_xfer into locked/unlocked versions.

Rename i2c_xfer to i2c_xfer_unlocked.  Audit all users of i2c_xfer to
see if they can use simple locking semantics or require their own
locking.  Since locked accesses are only safe for I2C_XFER_SINGLE
transactions, remove the flags parameter from i2c_xfer.  This also makes
the audit a bit easier.

Some remaining applications hold the bus locked across several
transactions that would otherwise be atomic, and a few others implement
complex I2C transactions in multiple commands.

Add a (nondeterministic) verification on the I2C port locking
correctness.  This will catch all statically incorrect locking patterns,
although dynamically incorrect locking patterns may not be caught.
Related: Revise the i2c_port_active_count to be a bitmap of the active
ports instead of a count of the active ports.  The EC's mutex does not
provide an is_locked() primitive, and we would prefer not to have one.

- board/glados: Custom locking for battery reset
- board/mchpevb1: Custom locking for battery reset
- board/oak: Custom locking for battery reset
- board/samus: Custom locking for lightbar reset
- board/sweetberry: simple locking
- board/servo_micro: Custom locking for funky i2c transfers
- capsense: simple locking
- host_command_master: multi-command transactions
- lb_common: manual locking to support samus power sequence
- smbus: multi-command transactions
- usb_i2c: simple locking
- driver/tcpm/fusb302: simple locking and multi-command transactions
- driver/tcpm/tcpi: Forward _unlocked and implicitly locked interface to
  fusb302
- driver/touchpad_elan: simple locking

BUG=chromium:871851
BRANCH=none
TEST=buildall; very careful audit
TEST=grunt clamshell and Coral clamshell, test boot, battery charging,
PD communication, and TCPC port low-power mode.
Signed-off-by: Jonathan Brandmeyer <jbrandmeyer@chromium.org>

Change-Id: Ieabf22bcab42780bdb994fca3ced5d8c62519d56
Reviewed-on: https://chromium-review.googlesource.com/1169913
Commit-Ready: Jonathan Brandmeyer <jbrandmeyer@chromium.org>
Tested-by: Jonathan Brandmeyer <jbrandmeyer@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Reviewed-by: Jett Rink <jettrink@chromium.org>

1 files changed, 3 insertions, 6 deletions

diff --git a/common/usb_i2c.c b/common/usb_i2c.c
index 4ceb4fe031..a92c411f1b 100644
--- a/common/usb_i2c.c
+++ b/common/usb_i2c.c
@@ -85,7 +85,6 @@ void usb_i2c_execute(struct usb_i2c_config const *config)
 	int write_count     = (config->buffer[1] >> 0) & 0xff;
 	int read_count      = (config->buffer[1] >> 8) & 0xff;
 	int offset          = 0;    /* Offset for extended reading header. */
-	int port;
 
 	config->buffer[0] = 0;
 	config->buffer[1] = 0;
@@ -117,14 +116,12 @@ void usb_i2c_execute(struct usb_i2c_config const *config)
 		 * knows about.  It should behave closer to
 		 * EC_CMD_I2C_PASSTHRU, which can protect ports and ranges.
 		 */
-		port = i2c_ports[portindex].port;
-		i2c_lock(port, 1);
-		ret = i2c_xfer(port, slave_addr,
+		ret = i2c_xfer(i2c_ports[portindex].port,
+				 slave_addr,
 				 (uint8_t *)(config->buffer + 2) + offset,
 				 write_count,
 				 (uint8_t *)(config->buffer + 2),
-				 read_count, I2C_XFER_SINGLE);
-		i2c_lock(port, 0);
+				 read_count);
 		config->buffer[0] = usb_i2c_map_error(ret);
 	}
 	usb_i2c_write_packet(config, read_count + 4);