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cros-ec: Avoid infinitely looping in google_chromeec_pd_get_amode 

Currently, google_chromeec_pd_get_amode infinitely loops if a TCPC port
is connected to a device with alternate mode(s) and the call is made
for the mode with the index higher than 0 (e.g. Zinger).

Cros EC manages alternative modes entered in an array (amode[]). The
command is designed to accept a query for an particular index and a
particular SVID.

Zinger has a 'Google' mode. It's stored in amode[0]. When AP queries
first time for DisplayPort with index=0, EC says 'no' as expected.

AP sends the next query with index=1 but EC_CMD_PROTO_VERSION (0x00)
is sent instead because cmd_code is cleared by google_chromeec_command.
res.svid is supposed to be 0 when EC hits the last index + 1 but
res.svid is set to 2 by the EC_CMD_PROTO_VERSION handler because
EC_PROTO_VERSION is currently 2. So, the call succeeds and AP goes to
the next index and this repeats forever.

Any USB-C device with non-DisplayPort alternate mode can cause this
hang unless HDMI port is used.

This patch resets all the fields of chromeec_command in each iteration
in case google_chromeec_command changes them.

BUG=b:78630899
BRANCH=none
TEST=Verify Fizz boots without monitors on Zinger. Verify the svid
enumeration happens as expected.

Change-Id: I388ed4bdfac9176d8e690c429e99674ed267004f
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-on: https://review.coreboot.org/25878
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
This commit is contained in:
Daisuke Nojiri 2018-04-26 12:59:58 -07:00 committed by Patrick Georgi
parent c01a9ab562
commit ccfa18feff
1 changed files with 14 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
src/ec/google/chromeec/ec.c
View File

@ -963,9 +963,13 @@ int google_chromeec_pd_get_amode(uint16_t svid)
for (i = 0; i < r.num_ports; i++) {
struct ec_params_usb_pd_get_mode_request p;
struct ec_params_usb_pd_get_mode_response res;
int svid_idx = 0;
do {
/* Reset cmd in each iteration in case
google_chromeec_command changes it. */
p.port = i;
p.svid_idx = 0;
p.svid_idx = svid_idx;
cmd.cmd_code = EC_CMD_USB_PD_GET_AMODE;
cmd.cmd_version = 0;
cmd.cmd_data_in = &p;
@ -974,12 +978,11 @@ int google_chromeec_pd_get_amode(uint16_t svid)
cmd.cmd_size_out = sizeof(res);
cmd.cmd_dev_index = 0;
do {
if (google_chromeec_command(&cmd) < 0)
return -1;
if (res.svid == svid)
return 1;
p.svid_idx++;
svid_idx++;
} while (res.svid);
}