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, 3 deletions

diff --git a/common/lb_common.c b/common/lb_common.c
index 2ffba93b2f..f800a6a65a 100644
--- a/common/lb_common.c
+++ b/common/lb_common.c
@@ -120,7 +120,7 @@ static inline void controller_write(int ctrl_num, uint8_t reg, uint8_t val)
 	buf[0] = reg;
 	buf[1] = val;
 	ctrl_num = ctrl_num % ARRAY_SIZE(i2c_addr);
-	i2c_xfer(I2C_PORT_LIGHTBAR, i2c_addr[ctrl_num], buf, 2, 0, 0,
+	i2c_xfer_unlocked(I2C_PORT_LIGHTBAR, i2c_addr[ctrl_num], buf, 2, 0, 0,
 		 I2C_XFER_SINGLE);
 }
 
@@ -130,8 +130,8 @@ static inline uint8_t controller_read(int ctrl_num, uint8_t reg)
 	int rv;
 
 	ctrl_num = ctrl_num % ARRAY_SIZE(i2c_addr);
-	rv = i2c_xfer(I2C_PORT_LIGHTBAR, i2c_addr[ctrl_num], &reg, 1, buf, 1,
-		      I2C_XFER_SINGLE);
+	rv = i2c_xfer_unlocked(I2C_PORT_LIGHTBAR, i2c_addr[ctrl_num],
+			&reg, 1, buf, 1, I2C_XFER_SINGLE);
 	return rv ? 0 : buf[0];
 }