spl: add serial download protocol (SDP) support

Add USB serial download protocol support to SPL. If the SoC started
in recovery mode the SPL will immediately switch to SDP and wait for
further downloads/commands from the host side.

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
Reviewed-by: Stefano Babic <sbabic@denx.de>
Reviewed-by: Łukasz Majewski <lukma@denx.de>

common/spl/Kconfig

@@ -668,6 +668,12 @@ config SPL_DFU_RAM
 
 endchoice
 
+config SPL_USB_SDP_SUPPORT
+	bool "Support SDP (Serial Download Protocol)"
+	help
+	  Enable Serial Download Protocol (SDP) device support in SPL. This
+	  allows to download images into memory and execute (jump to) them
+	  using the same protocol as implemented by the i.MX family's boot ROM.
 endif
 
 config SPL_WATCHDOG_SUPPORT

common/spl/Makefile

@@ -30,4 +30,5 @@ obj-$(CONFIG_$(SPL_TPL_)SATA_SUPPORT) += spl_sata.o
 obj-$(CONFIG_$(SPL_TPL_)DFU_SUPPORT) += spl_dfu.o
 obj-$(CONFIG_$(SPL_TPL_)SPI_LOAD) += spl_spi.o
 obj-$(CONFIG_$(SPL_TPL_)RAM_SUPPORT) += spl_ram.o
+obj-$(CONFIG_$(SPL_TPL_)USB_SDP_SUPPORT) += spl_sdp.o
 endif

common/spl/spl_sdp.c

@@ -0,0 +1,37 @@
+/*
+ * (C) Copyright 2016 Toradex
+ * Author: Stefan Agner <stefan.agner@toradex.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <spl.h>
+#include <usb.h>
+#include <g_dnl.h>
+#include <sdp.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+static int spl_sdp_load_image(struct spl_image_info *spl_image,
+			      struct spl_boot_device *bootdev)
+{
+	int ret;
+	const int controller_index = 0;
+
+	g_dnl_clear_detach();
+	g_dnl_register("usb_dnl_sdp");
+
+	ret = sdp_init(controller_index);
+	if (ret) {
+		error("SDP init failed: %d", ret);
+		return -ENODEV;
+	}
+
+	/* This command typically does not return but jumps to an image */
+	sdp_handle(controller_index);
+	error("SDP ended");
+
+	return -EINVAL;
+}
+SPL_LOAD_IMAGE_METHOD("USB SDP", 0, BOOT_DEVICE_BOARD, spl_sdp_load_image);

drivers/usb/gadget/Makefile

@@ -11,6 +11,7 @@ obj-$(CONFIG_USB_ETHER) += epautoconf.o config.o usbstring.o
 ifdef CONFIG_SPL_BUILD
 obj-$(CONFIG_SPL_USB_GADGET_SUPPORT) += g_dnl.o
 obj-$(CONFIG_SPL_DFU_SUPPORT) += f_dfu.o
+obj-$(CONFIG_SPL_USB_SDP_SUPPORT) += f_sdp.o
 endif
 
 # new USB gadget layer dependencies