programmer: Add Developerbox/CP2104 bit bang driver

The 96Boards Developerbox (a.k.a. Synquacer E-series) provides a CP2102
debug UART with its GPIO pins hooked up to the SPI NOR FLASH. The
circuit is intended to provide emergency recovery functions without
requiring any additional tools (such as a JTAG or SPI programmer). This
was expected to be very slow (and it is) but CP2102 is much cheaper than
a full dual channel USB comms chip.

Read performance is roughly on par with a 2400 baud modem (between 60
and 70 minutes per megabyte if you prefer) and write performance is 50%
slower still. The full recovery process, with backup and verification of
4MB data written takes between 14 and 15 hours. Thus it is only really
practical as an emergency recovery tool, firmware developers will need
to use an alternative programmer.

Change-Id: I2547a96c1a2259ad0d52cd4b6ef42261b37cccf3
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/26948
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

4 files changed, 278 insertions, 2 deletions

diff --git a/Makefile b/Makefile
index cd729724b..ddfd71169 100644
--- a/Makefile
+++ b/Makefile
@@ -154,12 +154,17 @@ UNSUPPORTED_FEATURES += CONFIG_PONY_SPI=yes
 else
 override CONFIG_PONY_SPI = no
 endif
-# Dediprog, USB-Blaster, PICkit2, CH341A and FT2232 are not supported under DOS (missing USB support).
+# Dediprog, Developerbox, USB-Blaster, PICkit2, CH341A and FT2232 are not supported under DOS (missing USB support).
 ifeq ($(CONFIG_DEDIPROG), yes)
 UNSUPPORTED_FEATURES += CONFIG_DEDIPROG=yes
 else
 override CONFIG_DEDIPROG = no
 endif
+ifeq ($(CONFIG_DEVELOPERBOX_SPI), yes)
+UNSUPPORTED_FEATURES += CONFIG_DEVELOPERBOX_SPI=yes
+else
+override CONFIG_DEVELOPERBOX_SPI = no
+endif
 ifeq ($(CONFIG_FT2232_SPI), yes)
 UNSUPPORTED_FEATURES += CONFIG_FT2232_SPI=yes
 else
@@ -311,12 +316,17 @@ UNSUPPORTED_FEATURES += CONFIG_PONY_SPI=yes
 else
 override CONFIG_PONY_SPI = no
 endif
-# Dediprog, USB-Blaster, PICkit2, CH341A and FT2232 are not supported with libpayload (missing libusb support).
+# Dediprog, Developerbox, USB-Blaster, PICkit2, CH341A and FT2232 are not supported with libpayload (missing libusb support).
 ifeq ($(CONFIG_DEDIPROG), yes)
 UNSUPPORTED_FEATURES += CONFIG_DEDIPROG=yes
 else
 override CONFIG_DEDIPROG = no
 endif
+ifeq ($(CONFIG_DEVELOPERBOX_SPI), yes)
+UNSUPPORTED_FEATURES += CONFIG_DEVELOPERBOX_SPI=yes
+else
+override CONFIG_DEVELOPERBOX_SPI = no
+endif
 ifeq ($(CONFIG_FT2232_SPI), yes)
 UNSUPPORTED_FEATURES += CONFIG_FT2232_SPI=yes
 else
@@ -627,6 +637,9 @@ CONFIG_BUSPIRATE_SPI ?= yes
 # Always enable Dediprog SF100 for now.
 CONFIG_DEDIPROG ?= yes
 
+# Always enable Developerbox emergency recovery for now.
+CONFIG_DEVELOPERBOX_SPI ?= yes
+
 # Always enable Marvell SATA controllers for now.
 CONFIG_SATAMV ?= yes
 
@@ -671,6 +684,7 @@ ifeq ($(CONFIG_ENABLE_LIBUSB1_PROGRAMMERS), no)
 override CONFIG_CH341A_SPI = no
 override CONFIG_DEDIPROG = no
 override CONFIG_DIGILENT_SPI = no
+override CONFIG_DEVELOPERBOX_SPI = no
 endif
 ifeq ($(CONFIG_ENABLE_LIBPCI_PROGRAMMERS), no)
 override CONFIG_INTERNAL = no
@@ -907,6 +921,12 @@ PROGRAMMER_OBJS += dediprog.o
 NEED_LIBUSB1 += CONFIG_DEDIPROG
 endif
 
+ifeq ($(CONFIG_DEVELOPERBOX_SPI), yes)
+FEATURE_CFLAGS += -D'CONFIG_DEVELOPERBOX_SPI=1'
+PROGRAMMER_OBJS += developerbox_spi.o
+NEED_LIBUSB1 += CONFIG_DEVELOPERBOX_SPI
+endif
+
 ifeq ($(CONFIG_SATAMV), yes)
 FEATURE_CFLAGS += -D'CONFIG_SATAMV=1'
 PROGRAMMER_OBJS += satamv.o
diff --git a/developerbox_spi.c b/developerbox_spi.c
new file mode 100644
index 000000000..8482dea17
--- /dev/null
+++ b/developerbox_spi.c
@@ -0,0 +1,232 @@
+/*
+ * This file is part of the flashrom project.
+ *
+ * Copyright (C) 2018 Linaro Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+/*
+ * Bit bang driver for the 96Boards Developerbox (a.k.a. Synquacer E-series)
+ * on-board debug UART.  The Developerbox implements its debug UART using a
+ * CP2102N, a USB to UART bridge which also provides four GPIO pins. On
+ * Developerbox these can be hooked up to the onboard SPI NOR FLASH and used
+ * for emergency de-brick without any additional hardware programmer. Bit
+ * banging over USB is extremely slow compared to a proper SPI programmer so
+ * this is only practical as a de-brick tool.
+ *
+ * Schematic is available here:
+ * https://www.96boards.org/documentation/enterprise/developerbox/hardware-docs/
+ *
+ * To prepare a Developerbox for programming via the debug UART, DSW4 must be
+ * changed from the default 00000000 to 10001000 (i.e. DSW4-1 and DSW4-5
+ * should be turned on).
+ */
+
+#include "platform.h"
+
+#include <stdlib.h>
+#include <string.h>
+#include <libusb.h>
+#include "programmer.h"
+#include "spi.h"
+
+/* Bit positions for each pin. */
+#define DEVELOPERBOX_SPI_SCK	0
+#define DEVELOPERBOX_SPI_CS	1
+#define DEVELOPERBOX_SPI_MISO	2
+#define DEVELOPERBOX_SPI_MOSI	3
+
+/* Config request types */
+#define REQTYPE_HOST_TO_DEVICE  0x40
+#define REQTYPE_DEVICE_TO_HOST  0xc0
+
+/* Config request codes */
+#define CP210X_VENDOR_SPECIFIC  0xff
+
+/* CP210X_VENDOR_SPECIFIC */
+#define CP210X_WRITE_LATCH      0x37e1
+#define CP210X_READ_LATCH       0x00c2
+
+const struct dev_entry devs_developerbox_spi[] = {
+	{0x10c4, 0xea60, OK, "Silicon Labs", "CP2102N USB to UART Bridge Controller"},
+	{0},
+};
+
+struct libusb_context *usb_ctx;
+static libusb_device_handle *cp210x_handle;
+
+static int cp210x_gpio_get(void)
+{
+	int res;
+	uint8_t gpio;
+
+	res = libusb_control_transfer(cp210x_handle, REQTYPE_DEVICE_TO_HOST,
+			CP210X_VENDOR_SPECIFIC, CP210X_READ_LATCH,
+			0, &gpio, 1, 0);
+	if (res < 0) {
+		msg_perr("Failed to read GPIO pins (%s)\n", libusb_error_name(res));
+		return 0;
+	}
+
+	return gpio;
+}
+
+static void cp210x_gpio_set(uint8_t val, uint8_t mask)
+{
+	int res;
+	uint16_t gpio;
+
+	gpio = ((val & 0xf) << 8) | (mask & 0xf);
+
+	/* Set relay state on the card */
+	res = libusb_control_transfer(cp210x_handle, REQTYPE_HOST_TO_DEVICE,
+			CP210X_VENDOR_SPECIFIC, CP210X_WRITE_LATCH,
+			gpio, NULL, 0, 0);
+	if (res < 0)
+		msg_perr("Failed to read GPIO pins (%s)\n", libusb_error_name(res));
+}
+
+static void cp210x_bitbang_set_cs(int val)
+{
+	cp210x_gpio_set(val << DEVELOPERBOX_SPI_CS, 1 << DEVELOPERBOX_SPI_CS);
+}
+
+static void cp210x_bitbang_set_sck(int val)
+{
+	cp210x_gpio_set(val << DEVELOPERBOX_SPI_SCK, 1 << DEVELOPERBOX_SPI_SCK);
+}
+
+static void cp210x_bitbang_set_mosi(int val)
+{
+	cp210x_gpio_set(val << DEVELOPERBOX_SPI_MOSI, 1 << DEVELOPERBOX_SPI_MOSI);
+}
+
+static int cp210x_bitbang_get_miso(void)
+{
+	return !!(cp210x_gpio_get() & (1 << DEVELOPERBOX_SPI_MISO));
+}
+
+static void cp210x_bitbang_set_sck_set_mosi(int sck, int mosi)
+{
+	cp210x_gpio_set(sck << DEVELOPERBOX_SPI_SCK | mosi << DEVELOPERBOX_SPI_MOSI,
+			  1 << DEVELOPERBOX_SPI_SCK |    1 << DEVELOPERBOX_SPI_MOSI);
+}
+
+static const struct bitbang_spi_master bitbang_spi_master_cp210x = {
+	.type = BITBANG_SPI_MASTER_DEVELOPERBOX,
+	.set_cs = cp210x_bitbang_set_cs,
+	.set_sck = cp210x_bitbang_set_sck,
+	.set_mosi = cp210x_bitbang_set_mosi,
+	.get_miso = cp210x_bitbang_get_miso,
+	.set_sck_set_mosi = cp210x_bitbang_set_sck_set_mosi,
+};
+
+static struct libusb_device_handle *get_device_by_vid_pid_serial(uint16_t vid, uint16_t pid,
+								 const char *serialno)
+{
+	struct libusb_device **list;
+	ssize_t count = libusb_get_device_list(usb_ctx, &list);
+	if (count < 0) {
+		msg_perr("Getting the USB device list failed (%s)!\n", libusb_error_name(count));
+		return NULL;
+	}
+
+	ssize_t i = 0;
+	for (i = 0; i < count; i++) {
+		struct libusb_device *dev = list[i];
+		struct libusb_device_descriptor desc;
+		struct libusb_device_handle *handle;
+
+		int res = libusb_get_device_descriptor(dev, &desc);
+		if (res != 0) {
+			msg_perr("Reading the USB device descriptor failed (%s)!\n", libusb_error_name(res));
+			continue;
+		}
+
+		if ((desc.idVendor != vid) && (desc.idProduct != pid))
+			continue;
+
+		msg_pdbg("Found USB device %04"PRIx16":%04"PRIx16" at address %d-%d.\n",
+			 desc.idVendor, desc.idProduct,
+			 libusb_get_bus_number(dev), libusb_get_device_address(dev));
+
+		res = libusb_open(dev, &handle);
+		if (res != 0) {
+			msg_perr("Opening the USB device failed (%s)!\n", libusb_error_name(res));
+			continue;
+		}
+
+		if (serialno) {
+			unsigned char myserial[64];
+			res = libusb_get_string_descriptor_ascii(handle, desc.iSerialNumber, myserial,
+								 sizeof(myserial));
+			if (res < 0) {
+				msg_perr("Reading the USB serialno failed (%s)!\n", libusb_error_name(res));
+				libusb_close(handle);
+				continue;
+			}
+			msg_pdbg("Serial number is %s\n", myserial);
+
+			/* Filter out any serial number that does not commence with serialno */
+			if (0 != strncmp(serialno, (char *) myserial, strlen(serialno))) {
+				libusb_close(handle);
+				continue;
+			}
+		}
+
+		libusb_free_device_list(list, 1);
+		return handle;
+	}
+
+	libusb_free_device_list(list, 1);
+	return NULL;
+}
+
+static int developerbox_spi_shutdown(void *data)
+{
+	libusb_close(cp210x_handle);
+	libusb_exit(usb_ctx);
+
+	return 0;
+}
+
+int developerbox_spi_init(void)
+{
+	libusb_init(&usb_ctx);
+	if (!usb_ctx) {
+		msg_perr("Could not initialize libusb!\n");
+		return 1;
+	}
+
+	char *serialno = extract_programmer_param("serial");
+	if (serialno)
+		msg_pdbg("Looking for serial number commencing %s\n", serialno);
+	cp210x_handle = get_device_by_vid_pid_serial(
+			devs_developerbox_spi[0].vendor_id, devs_developerbox_spi[0].device_id, serialno);
+	free(serialno);
+	if (!cp210x_handle) {
+		msg_perr("Could not find a Developerbox programmer on USB.\n");
+		goto err_exit;
+	}
+
+	if (register_shutdown(developerbox_spi_shutdown, NULL))
+		goto err_exit;
+
+	if (register_spi_bitbang_master(&bitbang_spi_master_cp210x))
+		goto err_exit;
+
+	return 0;
+
+err_exit:
+	libusb_exit(usb_ctx);
+	return 1;
+}
diff --git a/flashrom.c b/flashrom.c
index 1866a18ae..094630ccf 100644
--- a/flashrom.c
+++ b/flashrom.c
@@ -255,6 +255,18 @@ const struct programmer_entry programmer_table[] = {
 	},
 #endif
 
+#if CONFIG_DEVELOPERBOX_SPI == 1
+	{
+		.name			= "developerbox",
+		.type			= USB,
+		.devs.dev		= devs_developerbox_spi,
+		.init			= developerbox_spi_init,
+		.map_flash_region	= fallback_map,
+		.unmap_flash_region	= fallback_unmap,
+		.delay			= internal_delay,
+	},
+#endif
+
 #if CONFIG_RAYER_SPI == 1
 	{
 		.name			= "rayer_spi",
diff --git a/programmer.h b/programmer.h
index 7e530b632..300cf5f16 100644
--- a/programmer.h
+++ b/programmer.h
@@ -73,6 +73,9 @@ enum programmer {
 #if CONFIG_DEDIPROG == 1
 	PROGRAMMER_DEDIPROG,
 #endif
+#if CONFIG_DEVELOPERBOX_SPI == 1
+	PROGRAMMER_DEVELOPERBOX_SPI,
+#endif
 #if CONFIG_RAYER_SPI == 1
 	PROGRAMMER_RAYER_SPI,
 #endif
@@ -172,6 +175,9 @@ enum bitbang_spi_master_type {
 #if CONFIG_OGP_SPI == 1
 	BITBANG_SPI_MASTER_OGP,
 #endif
+#if CONFIG_DEVELOPERBOX_SPI == 1
+	BITBANG_SPI_MASTER_DEVELOPERBOX,
+#endif
 };
 
 struct bitbang_spi_master {
@@ -548,6 +554,12 @@ int dediprog_init(void);
 extern const struct dev_entry devs_dediprog[];
 #endif
 
+/* developerbox_spi.c */
+#if CONFIG_DEVELOPERBOX_SPI == 1
+int developerbox_spi_init(void);
+extern const struct dev_entry devs_developerbox_spi[];
+#endif
+
 /* ch341a_spi.c */
 #if CONFIG_CH341A_SPI == 1
 int ch341a_spi_init(void);