TCPMv2: Trigger ErrorRecovery for FRS corner cases

Currently, if the port partner sends a Hard Reset during the FRS
sequence, we attempt to handle the Hard Reset.  However, this leaves us
in an inconsistent power state which can lead to the DUT sourcing itself
while neither partner presents Rp.  Instead, go to ErrorRecovery which
is the general method of recovering from anything unexpected during the
FRS sequence.

Additionally, correct the state machine to go to ErrorRecovery on
discard as well and when we receive a SoftReset in the middle of the FRS
sequence.

BRANCH=None
BUG=b:266035645
TEST=on frostflow, trigger FRS with problematic dock and observe Chrome
does not show charging
LOW_COVERAGE_REASON=FRS support in the partner emulator needs expanded,
filed b/269473786 to track this

Change-Id: Icd3a9da52534ecbb9012b740b082938f66052c22
Signed-off-by: Diana Z <dzigterman@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/4209978
Reviewed-by: Abe Levkoy <alevkoy@chromium.org>

1 files changed, 17 insertions, 5 deletions

diff --git a/common/usbc/usb_pe_drp_sm.c b/common/usbc/usb_pe_drp_sm.c
index 5eb983a89c..3037ed1fca 100644
--- a/common/usbc/usb_pe_drp_sm.c
+++ b/common/usbc/usb_pe_drp_sm.c
@@ -911,6 +911,15 @@ void pe_got_hard_reset(int port)
 	assert(port == TASK_ID_TO_PD_PORT(task_get_current()));
 
 	/*
+	 * If we're in the middle of an FRS, any error should cause us to follow
+	 * the ErrorRecovery path
+	 */
+	if (pe_in_frs_mode(port)) {
+		set_state_pe(port, PE_WAIT_FOR_ERROR_RECOVERY);
+		return;
+	}
+
+	/*
 	 * Transition from any state to the PE_SRC_Hard_Reset_Received or
 	 *  PE_SNK_Transition_to_default state when:
 	 *  1) Hard Reset Signaling is detected.
@@ -1263,8 +1272,12 @@ void pe_got_soft_reset(int port)
 	/*
 	 * The PE_SRC_Soft_Reset state Shall be entered from any state when a
 	 * Soft_Reset Message is received from the Protocol Layer.
+	 *
+	 * However, if we're in the middle of an FRS sequence, we need to go to
+	 * ErrorRecovery instead.
 	 */
-	set_state_pe(port, PE_SOFT_RESET);
+	set_state_pe(port, pe_in_frs_mode(port) ? PE_WAIT_FOR_ERROR_RECOVERY :
+						  PE_SOFT_RESET);
 }
 
 __overridable bool pd_can_charge_from_device(int port, const int pdo_cnt,
@@ -5151,10 +5164,9 @@ static void pe_prs_snk_src_send_swap_run(int port)
 	 * Handle discarded message
 	 */
 	if (msg_check & PE_MSG_DISCARDED) {
-		if (pe_in_frs_mode(port))
-			pe_set_hard_reset(port);
-		else
-			set_state_pe(port, PE_SNK_READY);
+		set_state_pe(port, pe_in_frs_mode(port) ?
+					   PE_WAIT_FOR_ERROR_RECOVERY :
+					   PE_SNK_READY);
 		return;
 	}