Add primitive support for serial1 as the upstream port

Signed-off-by: Marc Zyngier <maz@kernel.org>

3 files changed, 100 insertions, 5 deletions

diff --git a/m1-pd-bmc.h b/m1-pd-bmc.h
index 6edc509..616b6d8 100644
--- a/m1-pd-bmc.h
+++ b/m1-pd-bmc.h
@@ -52,6 +52,8 @@ struct upstream_ops {
 };
 
 extern const struct upstream_ops *upstream_ops;
+void set_upstream_ops(bool serial);
+bool upstream_is_serial(void);
 
 void upstream_tx_str(int32_t port, const char *ptr);
 
diff --git a/start.c b/start.c
index 10c4394..d80acdd 100644
--- a/start.c
+++ b/start.c
@@ -96,6 +96,16 @@ static const struct gpio_pin_config m1_pd_bmc_pin_config1[] = {
 	},
 };
 
+static struct {
+	/*
+	 * we rely on prod/cons rollover behaviour, and buf must cover
+	 * the full range of prod/cons.
+	 */
+	uint8_t		prod;
+	uint8_t		cons;
+	char		buf[256];
+} uart1_buf;
+
 static void __not_in_flash_func(uart_irq_fn)(int port,
 					     const struct hw_context *hw)
 {
@@ -135,7 +145,18 @@ static void __not_in_flash_func(uart0_irq_fn)(void)
 
 static void __not_in_flash_func(uart1_irq_fn)(void)
 {
-	uart_irq_fn(1, &hw1);
+	if (!upstream_is_serial()) {
+		uart_irq_fn(1, &hw1);
+		return;
+	}
+
+	while (uart_is_readable(uart1)) {
+		uart1_buf.buf[uart1_buf.prod++] = uart_getc(uart1);
+
+		/* Oops, we're losing data... */
+		if (uart1_buf.prod == uart1_buf.cons)
+			uart1_buf.cons++;
+	}
 }
 
 static void init_system(const struct hw_context *hw)
@@ -217,6 +238,41 @@ static const struct upstream_ops usb_upstream_ops = {
 	.flush		= tud_task,
 };
 
+static void serial1_tx_bytes(int32_t port, const char *ptr, int len)
+{
+	uart_write_blocking(uart1, ptr, len);
+}
+
+static int32_t serial1_rx_byte(int32_t port)
+{
+	uint32_t status;
+	int32_t val;
+
+	tud_task();
+	val = usb_rx_byte(port);
+	if (val != -1)
+		return val;
+
+	status = save_and_disable_interrupts();
+
+	if (uart1_buf.prod == uart1_buf.cons)
+		val = -1;
+	else
+		val = uart1_buf.buf[uart1_buf.cons++];
+
+	restore_interrupts(status);
+
+	return val;
+}
+
+static void serial1_flush(void) {}
+
+static const struct upstream_ops serial1_upstream_ops = {
+	.tx_bytes	= serial1_tx_bytes,
+	.rx_byte	= serial1_rx_byte,
+	.flush		= serial1_flush,
+};
+
 const struct upstream_ops *upstream_ops;
 
 void upstream_tx_str(int32_t port, const char *str)
@@ -238,12 +294,28 @@ void upstream_tx_str(int32_t port, const char *str)
 	} while (*str);
 }
 
+void set_upstream_ops(bool serial)
+{
+	if (serial) {
+		upstream_ops = &serial1_upstream_ops;
+	} else {
+		upstream_ops = &usb_upstream_ops;
+	}
+
+	__dsb();
+}
+
+bool upstream_is_serial(void)
+{
+	return upstream_ops == &serial1_upstream_ops;
+}
+
 int main(void)
 {
 	bool success;
 	int port;
 
-	upstream_ops = &usb_upstream_ops;
+	set_upstream_ops(false);
 
 	success = set_sys_clock_khz(133000, false);
 
diff --git a/vdmtool.c b/vdmtool.c
index 54b2c26..ddf7ba4 100644
--- a/vdmtool.c
+++ b/vdmtool.c
@@ -474,8 +474,14 @@ static void help(struct vdm_context *cxt)
 		"^_ ^D Toggle debug\n"
 		"^_ ^M Send empty debug VDM\n"
 		"^_ 1  Serial on Primary USB pins\n"
-		"^_ 2  Serial on SBU pins\n"
-		"^_ ?  This message\n");
+		"^_ 2  Serial on SBU pins\n");
+
+	if (upstream_is_serial())
+		cprintf_cont(cxt, "^_ ^@  Send break\n");
+	if (PORT(cxt) == 0 && !vdm_contexts[1].hw)
+		cprintf_cont(cxt, "^_ ^U  Switch upstream port USB/Serial\n");
+	cprintf_cont(cxt, "^_ ?  This message\n");
+
 	for (int i = 0; i < CONFIG_USB_PD_PORT_COUNT; i++) {
 		struct vdm_context *tmp = &vdm_contexts[i];
 
@@ -483,9 +489,10 @@ static void help(struct vdm_context *cxt)
 			PORT(tmp),
 			tmp->hw ? "present" : "absent");
 		if (tmp->hw)
-			cprintf_cont(cxt, ",cc%d,%s%s",
+			cprintf_cont(cxt, ",cc%d,%s,%s%s",
 				     tmp->cc_line + 1,
 				     pinsets[tmp->serial_pin_set],
+				     upstream_is_serial() ? "serial" : "USB",
 				     tmp->verbose ? ",debug" : "");
 		cprintf_cont(cxt, "\n");
 	}
@@ -547,6 +554,9 @@ static bool serial_handler(struct vdm_context *cxt)
 			cxt->verbose = !cxt->verbose;
 			cprintf(cxt, "Debug o%s\n", cxt->verbose ? "n" : "ff");
 			break;
+		case 0:				/* ^@ */
+			tud_cdc_send_break_cb(PORT(cxt), 100);
+			break;
 		case '\r':			/* Enter */
 			debug_poke(cxt);
 			break;
@@ -554,6 +564,17 @@ static bool serial_handler(struct vdm_context *cxt)
 			cxt->serial_pin_set = c - '0';
 			vdm_pd_reset(cxt);
 			break;
+		case 0x15:     			/* ^U */
+			/* We can't do that if port 1 exists */
+			if (PORT(cxt) != 0 || vdm_contexts[1].hw)
+				break;
+
+			cprintf(cxt, "Upstream switching to %s\n",
+				!upstream_is_serial() ? "serial" : "USB");
+			set_upstream_ops(!upstream_is_serial());
+			cprintf(cxt, "Upstream is %s\n",
+				upstream_is_serial() ? "serial" : "USB");
+			break;
 		case 0x18:			/* ^X */
 			cxt->pending = true;
 			evt_disconnect(cxt);