syv682X: Add support for FRS

Add interrupt for FRS signal and implement function to enable FRS by
setting the FRS gpio. Only the TCPMv2 stack works with FRS.

There are 2 workarounds in this CL for this version of the SYV682:
1. Only use the CC trigger when charging at 5V. If charging at greater
than vSafe5V, just use VBUS falling to detect an FRS.
2. Use the TCPC CC trigger if available to signal FRS to the TCPM.

BUG=b:148144711
TEST=make buildall
TEST=After enabling FRS config options, check that FRS occurs and is
properly signaled to the TCPM
BRANCH=none

Change-Id: Icd1ef8902925817ea5948b42f03b292a97a2b5bd
Signed-off-by: Eric Herrmann <eherrmann@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2277209
Reviewed-by: Keith Short <keithshort@chromium.org>

1 files changed, 105 insertions, 9 deletions

diff --git a/driver/ppc/syv682x.c b/driver/ppc/syv682x.c
index fc7b37460f..c88ae9346b 100644
--- a/driver/ppc/syv682x.c
+++ b/driver/ppc/syv682x.c
@@ -44,6 +44,13 @@ static timestamp_t oc_timer[CONFIG_USB_PD_PORT_MAX_COUNT];
 #error "SOURCE_OC_DEGLITCH_MS should be at least INTERRUPT_DELAY_MS"
 #endif
 
+/* When FRS is enabled, the VCONN line isn't passed through to the TCPC */
+#if defined(CONFIG_USB_PD_FRS_PPC) && defined(CONFIG_USBC_VCONN) && \
+	!defined(CONFIG_USBC_PPC_VCONN)
+#error "if FRS is enabled on the SYV682X, VCONN must be supplied by the PPC "
+"instead of the TCPC"
+#endif
+
 #define CPRINTS(format, args...) cprints(CC_USBPD, format, ## args)
 
 static int read_reg(uint8_t port, int reg, int *regval)
@@ -189,6 +196,26 @@ static bool syv682x_interrupt_filter(int port, int regval, int regmask,
  */
 static void syv682x_handle_status_interrupt(int port, int regval)
 {
+	/* An FRS will automatically enable the source path */
+	if (IS_ENABLED(CONFIG_USB_PD_FRS_PPC) &&
+	    (regval & SYV682X_STATUS_FRS)) {
+		flags[port] |= SYV682X_FLAGS_SOURCE_ENABLED;
+		/*
+		 * Workaround for bug in SYV692.
+		 *
+		 * The SYV682X has an FRS trigger but it is broken in some
+		 * versions of the part. The old parts require VBUS to fall to
+		 * generate the interrupt, it needs to be generated on CC alone.
+		 *
+		 * The workaround is to use to the TCPC trigger if
+		 * available. When the part is fixed, the TCPC trigger is no
+		 * longer needed. If the TCPC doesn't have a trigger, FRS timing
+		 * may be violated for slow-vbus discharge cases.
+		 */
+		if (!IS_ENABLED(CONFIG_USB_PD_FRS_TCPC))
+			pd_got_frs_signal(port);
+	}
+
 	/* These conditions automatically turn off VBUS sourcing */
 	if (regval & (SYV682X_STATUS_OVP | SYV682X_STATUS_TSD))
 		flags[port] &= ~SYV682X_FLAGS_SOURCE_ENABLED;
@@ -387,12 +414,12 @@ static int syv682x_set_vconn(int port, int enable)
 	 */
 	syv682x_handle_control_4_interrupt(port, regval);
 
-	if (enable)
+	regval &= ~(SYV682X_CONTROL_4_VCONN2 | SYV682X_CONTROL_4_VCONN1);
+	if (enable) {
 		regval |= flags[port] & SYV682X_FLAGS_CC_POLARITY ?
-			SYV682X_CONTROL_4_VCONN1 : SYV682X_CONTROL_4_VCONN2;
-	else
-		regval &= ~(SYV682X_CONTROL_4_VCONN2 |
-			    SYV682X_CONTROL_4_VCONN1);
+				  SYV682X_CONTROL_4_VCONN1 :
+				  SYV682X_CONTROL_4_VCONN2;
+	}
 
 	return write_reg(port, SYV682X_CONTROL_4_REG, regval);
 }
@@ -480,6 +507,71 @@ void syv682x_interrupt(int port)
 	syv682x_interrupt_delayed(port, 0);
 }
 
+/*
+ * The frs_en signal can be driven from the TCPC as well (preferred).
+ * In that case, no PPC configuration needs to be done to enable FRS
+ */
+#ifdef CONFIG_USB_PD_FRS_PPC
+static int syv682x_set_frs_enable(int port, int enable)
+{
+	int status;
+	int regval;
+
+	read_reg(port, SYV682X_CONTROL_4_REG, &regval);
+	syv682x_handle_control_4_interrupt(port, regval);
+
+	if (enable) {
+		read_reg(port, SYV682X_STATUS_REG, &status);
+		syv682x_handle_status_interrupt(port, status);
+		/*
+		 * Workaround for a bug in SYV682A
+		 *
+		 * The bug is that VBUS needs to be below VBAT when CC is pulled
+		 * low to trigger FRS. This is fine when charging at 5V usually,
+		 * but often not when charging at higher voltages. At higher
+		 * voltages, the CC trigger needs to be disabled for the broken
+		 * parts.
+		 *
+		 * TODO (b/161372139): When this is fixed in SYV682B, always use
+		 * the CC trigger.
+		 */
+		if (status & SYV682X_STATUS_VSAFE_5V) {
+			/* Inverted register, clear to enable CC detection */
+			regval &= ~SYV682X_CONTROL_4_CC_FRS;
+			/*
+			 * The CC line is the FRS trigger, and VCONN should
+			 * be ignored. The SYV682 uses the CCx_BPS fields to
+			 * determine if CC1 or CC2 is CC and should be used for
+			 * FRS. This CCx is also connected through to the TCPC.
+			 * The other CCx signal (VCONN) is isolated from the
+			 * TCPC with this write (VCONN must be provided by PPC)
+			 *
+			 * It is not a valid state to have both or neither
+			 * CC_BPS bits set and the CC_FRS enabled, exactly 1
+			 * should be set.
+			 */
+			regval &= ~(SYV682X_CONTROL_4_CC1_BPS |
+				    SYV682X_CONTROL_4_CC2_BPS);
+			regval |= flags[port] & SYV682X_FLAGS_CC_POLARITY ?
+					  SYV682X_CONTROL_4_CC2_BPS :
+					  SYV682X_CONTROL_4_CC1_BPS;
+
+		} else {
+			regval |= SYV682X_CONTROL_4_CC_FRS;
+		}
+	} else {
+		/*
+		 * Disabling FRS is part of the disconnect sequence, reconnect
+		 * CC lines to TCPC.
+		 */
+		regval |= SYV682X_CONTROL_4_CC1_BPS | SYV682X_CONTROL_4_CC2_BPS;
+	}
+	write_reg(port, SYV682X_CONTROL_4_REG, regval);
+	gpio_set_level(ppc_chips[port].frs_en, enable);
+	return EC_SUCCESS;
+}
+#endif /*CONFIG_USB_PD_FRS_PPC*/
+
 static bool syv682x_is_sink(uint8_t control_1)
 {
 	/*
@@ -574,11 +666,12 @@ static int syv682x_init(int port)
 		return rv;
 
 	/*
-	 * Remove Rd, connect CC1/CC2 lines to TCPC, and disable fast role
-	 * swap.
+	 * Remove Rd and connect CC1/CC2 lines to TCPC
+	 * Disable Vconn
+	 * Disable CC detection of Fast Role Swap (FRS)
 	 */
-	regval = SYV682X_CONTROL_4_CC1_BPS | SYV682X_CONTROL_4_CC2_BPS
-		| SYV682X_CONTROL_4_CC_FRS;
+	regval = SYV682X_CONTROL_4_CC1_BPS | SYV682X_CONTROL_4_CC2_BPS |
+		 SYV682X_CONTROL_4_CC_FRS;
 	rv = write_reg(port, SYV682X_CONTROL_4_REG, regval);
 	if (rv)
 		return rv;
@@ -594,6 +687,9 @@ const struct ppc_drv syv682x_drv = {
 #ifdef CONFIG_CMD_PPC_DUMP
 	.reg_dump = &syv682x_dump,
 #endif /* defined(CONFIG_CMD_PPC_DUMP) */
+#ifdef CONFIG_USB_PD_FRS_PPC
+	.set_frs_enable = &syv682x_set_frs_enable,
+#endif
 #ifdef CONFIG_USB_PD_VBUS_DETECT_PPC
 	.is_vbus_present = &syv682x_is_vbus_present,
 #endif /* defined(CONFIG_USB_PD_VBUS_DETECT_PPC) */