stm32-USB: USB SPI tunnel driver

Simple control of SPI for flashing over USB.

This driver is working, and using the discovery board
with a W25Q16 flash chip attached flashrom can read,
erase, write, and verify the whole chip in 45 seconds.

Signed-off-by: Anton Staaf <robotboy@chromium.org>

BRANCH=None
BUG=None
TEST=make buildall -j

Change-Id: I224f1f87cd6adc8b64c17de1df98dae0a9cfa6a5
Reviewed-on: https://chromium-review.googlesource.com/218740
Reviewed-by: Anton Staaf <robotboy@chromium.org>
Tested-by: Anton Staaf <robotboy@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Commit-Queue: Anton Staaf <robotboy@chromium.org>

3 files changed, 297 insertions, 0 deletions

diff --git a/chip/stm32/build.mk b/chip/stm32/build.mk
index 152b1e9b7a..57b711f094 100644
--- a/chip/stm32/build.mk
+++ b/chip/stm32/build.mk
@@ -51,3 +51,4 @@ chip-$(CONFIG_USB_GPIO)+=usb_gpio.o
 chip-$(CONFIG_USB_HID)+=usb_hid.o
 chip-$(CONFIG_USB_MS)+=usb_ms.o usb_ms_scsi.o
 chip-$(CONFIG_USB_POWER_DELIVERY)+=usb_pd_phy.o
+chip-$(CONFIG_USB_SPI)+=usb_spi.o
diff --git a/chip/stm32/usb_spi.c b/chip/stm32/usb_spi.c
new file mode 100644
index 0000000000..6140f4629b
--- /dev/null
+++ b/chip/stm32/usb_spi.c
@@ -0,0 +1,124 @@
+/* Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "common.h"
+#include "link_defs.h"
+#include "registers.h"
+#include "spi.h"
+#include "usb.h"
+#include "usb_spi.h"
+
+static int16_t usb_spi_map_error(int error)
+{
+	switch (error) {
+	case EC_SUCCESS:       return usb_spi_success;
+	case EC_ERROR_TIMEOUT: return usb_spi_timeout;
+	case EC_ERROR_BUSY:    return usb_spi_busy;
+	default:               return usb_spi_unknown_error | (error & 0x7fff);
+	}
+}
+
+static uint8_t usb_spi_read_packet(struct usb_spi_config const *config)
+{
+	size_t  i;
+	uint8_t count = btable_ep[config->endpoint].rx_count & 0x3ff;
+
+	/*
+	 * The USB peripheral doesn't support DMA access to its packet
+	 * RAM so we have to copy messages out into a bounce buffer.
+	 */
+	for (i = 0; i < (count + 1) / 2; ++i)
+		config->buffer[i] = config->rx_ram[i];
+
+	/*
+	 * RX packet consumed, mark the packet as VALID.  The master
+	 * could queue up the next command while we process this SPI
+	 * transaction and prepare the response.
+	 */
+	STM32_TOGGLE_EP(config->endpoint, EP_RX_MASK, EP_RX_VALID, 0);
+
+	return count;
+}
+
+static void usb_spi_write_packet(struct usb_spi_config const *config,
+				 uint8_t count)
+{
+	size_t  i;
+
+	/*
+	 * Copy read bytes and status back out of bounce buffer and
+	 * update TX packet state (mark as VALID for master to read).
+	 */
+	for (i = 0; i < (count + 1) / 2; ++i)
+		config->tx_ram[i] = config->buffer[i];
+
+	btable_ep[config->endpoint].tx_count = count;
+
+	STM32_TOGGLE_EP(config->endpoint, EP_TX_MASK, EP_TX_VALID, 0);
+}
+
+static int rx_valid(struct usb_spi_config const *config)
+{
+	return (STM32_USB_EP(config->endpoint) & EP_RX_MASK) == EP_RX_VALID;
+}
+
+int usb_spi_service_request(struct usb_spi_config const *config)
+{
+	uint8_t count;
+	uint8_t write_count;
+	uint8_t read_count;
+
+	if (rx_valid(config))
+		return 0;
+
+	count       = usb_spi_read_packet(config);
+	write_count = (config->buffer[0] >> 0) & 0xff;
+	read_count  = (config->buffer[0] >> 8) & 0xff;
+
+	if (write_count > USB_SPI_MAX_WRITE_COUNT ||
+	    write_count != (count - 2)) {
+		config->buffer[0] = usb_spi_write_count_invalid;
+	} else if (read_count > USB_SPI_MAX_READ_COUNT) {
+		config->buffer[0] = usb_spi_read_count_invalid;
+	} else {
+		config->buffer[0] = usb_spi_map_error(
+			spi_transaction((uint8_t *)(config->buffer + 1),
+					write_count,
+					(uint8_t *)(config->buffer + 1),
+					read_count));
+	}
+
+	usb_spi_write_packet(config, read_count + 2);
+
+	return 1;
+}
+
+void usb_spi_tx(struct usb_spi_config const *config)
+{
+	STM32_TOGGLE_EP(config->endpoint, EP_TX_MASK, EP_TX_NAK, 0);
+}
+
+void usb_spi_rx(struct usb_spi_config const *config)
+{
+	STM32_TOGGLE_EP(config->endpoint, EP_RX_MASK, EP_RX_NAK, 0);
+	config->ready(config);
+}
+
+void usb_spi_reset(struct usb_spi_config const *config)
+{
+	int endpoint = config->endpoint;
+
+	btable_ep[endpoint].tx_addr  = usb_sram_addr(config->tx_ram);
+	btable_ep[endpoint].tx_count = 0;
+
+	btable_ep[endpoint].rx_addr  = usb_sram_addr(config->rx_ram);
+	btable_ep[endpoint].rx_count =
+		0x8000 | ((USB_MAX_PACKET_SIZE / 32 - 1) << 10);
+
+	STM32_USB_EP(endpoint) = ((endpoint <<  0) | /* Endpoint Addr*/
+				  (2        <<  4) | /* TX NAK */
+				  (0        <<  9) | /* Bulk EP */
+				  (3        << 12)); /* RX Valid */
+}
diff --git a/chip/stm32/usb_spi.h b/chip/stm32/usb_spi.h
new file mode 100644
index 0000000000..a90898578d
--- /dev/null
+++ b/chip/stm32/usb_spi.h
@@ -0,0 +1,172 @@
+/* Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#ifndef CHIP_STM32_USB_SPI_H
+#define CHIP_STM32_USB_SPI_H
+
+/* STM32 USB SPI driver for Chrome EC */
+
+#include "compile_time_macros.h"
+#include "usb.h"
+
+/*
+ * Command:
+ *     +------------------+-----------------+------------------------+
+ *     | write count : 1B | read count : 1B | write payload : <= 62B |
+ *     +------------------+-----------------+------------------------+
+ *
+ *     write count:   1 byte, zero based count of bytes to write
+ *
+ *     read count:    1 byte, zero based count of bytes to read
+ *
+ *     write payload: up to 62 bytes of data to write, length must match
+ *                    write count
+ *
+ * Response:
+ *     +-------------+-----------------------+
+ *     | status : 2B | read payload : <= 62B |
+ *     +-------------+-----------------------+
+ *
+ *     status: 2 byte status
+ *         0x0000: Success
+ *         0x0001: SPI timeout
+ *         0x0002: Busy, try again
+ *             This can happen if someone else has acquired the shared memory
+ *             buffer that the SPI driver uses as /dev/null
+ *         0x0003: Write count invalid (> 62 bytes, or mismatch with payload)
+ *         0x0004: Read count invalid (> 62 bytes)
+ *         0x8000: Unknown error mask
+ *             The bottom 15 bits will contain the bottom 15 bits from the EC
+ *             error code.
+ *
+ *     read payload: up to 62 bytes of data read from SPI, length will match
+ *                   requested read count
+ */
+
+enum usb_spi_error {
+	usb_spi_success             = 0x0000,
+	usb_spi_timeout             = 0x0001,
+	usb_spi_busy                = 0x0002,
+	usb_spi_write_count_invalid = 0x0003,
+	usb_spi_read_count_invalid  = 0x0004,
+	usb_spi_unknown_error       = 0x8000,
+};
+
+#define USB_SPI_MAX_WRITE_COUNT 62
+#define USB_SPI_MAX_READ_COUNT  62
+
+BUILD_ASSERT(USB_MAX_PACKET_SIZE == (1 + 1 + USB_SPI_MAX_WRITE_COUNT));
+BUILD_ASSERT(USB_MAX_PACKET_SIZE == (2 + USB_SPI_MAX_READ_COUNT));
+
+/*
+ * Compile time Per-USB gpio configuration stored in flash.  Instances of this
+ * structure are provided by the user of the USB gpio.  This structure binds
+ * together all information required to operate a USB gpio.
+ */
+struct usb_spi_config {
+	/*
+	 * Endpoint index, and pointers to the USB packet RAM buffers.
+	 */
+	int endpoint;
+
+	/*
+	 * Pointers to USB packet RAM and bounce buffer.
+	 */
+	uint16_t *buffer;
+	usb_uint *rx_ram;
+	usb_uint *tx_ram;
+
+	/*
+	 * Callback to notify managing task that a new SPI request has been
+	 * received.  This should wake up a task that will eventually call
+	 * the usb_spi_service_request function.
+	 */
+	void (*ready)(struct usb_spi_config const *config);
+};
+
+/*
+ * Convenience macro for defining a USB SPI bridge driver.
+ *
+ * NAME is used to construct the names of the trampoline functions and the
+ * usb_spi_config struct, the latter is just called NAME.
+ *
+ * INTERFACE is the index of the USB interface to associate with this
+ * SPI driver.
+ *
+ * ENDPOINT is the index of the USB bulk endpoint used for receiving and
+ * transmitting bytes.
+ *
+ * READY callback function for command reception notification.
+ */
+#define USB_SPI_CONFIG(NAME,						\
+		       INTERFACE,					\
+		       ENDPOINT,					\
+		       READY)						\
+	static uint16_t CONCAT2(NAME, _buffer)[USB_MAX_PACKET_SIZE / 2]; \
+	static usb_uint CONCAT2(NAME, _ep_rx_buffer)[USB_MAX_PACKET_SIZE / 2] __usb_ram; \
+	static usb_uint CONCAT2(NAME, _ep_tx_buffer)[USB_MAX_PACKET_SIZE / 2] __usb_ram; \
+	struct usb_spi_config const NAME = {				\
+		.endpoint  = ENDPOINT,					\
+		.buffer    = CONCAT2(NAME, _buffer),			\
+		.rx_ram    = CONCAT2(NAME, _ep_rx_buffer),		\
+		.tx_ram    = CONCAT2(NAME, _ep_tx_buffer),		\
+		.ready     = READY,					\
+	};								\
+	const struct usb_interface_descriptor				\
+	USB_IFACE_DESC(INTERFACE) = {					\
+		.bLength            = USB_DT_INTERFACE_SIZE,		\
+		.bDescriptorType    = USB_DT_INTERFACE,			\
+		.bInterfaceNumber   = INTERFACE,			\
+		.bAlternateSetting  = 0,				\
+		.bNumEndpoints      = 2,				\
+		.bInterfaceClass    = USB_CLASS_VENDOR_SPEC,		\
+		.bInterfaceSubClass = 0,				\
+		.bInterfaceProtocol = 0,				\
+		.iInterface         = 0,				\
+	};								\
+	const struct usb_endpoint_descriptor				\
+	USB_EP_DESC(INTERFACE, 0) = {					\
+		.bLength          = USB_DT_ENDPOINT_SIZE,		\
+		.bDescriptorType  = USB_DT_ENDPOINT,			\
+		.bEndpointAddress = 0x80 | ENDPOINT,			\
+		.bmAttributes     = 0x02 /* Bulk IN */,			\
+		.wMaxPacketSize   = USB_MAX_PACKET_SIZE,		\
+		.bInterval        = 10,					\
+	};								\
+	const struct usb_endpoint_descriptor				\
+	USB_EP_DESC(INTERFACE, 1) = {					\
+		.bLength          = USB_DT_ENDPOINT_SIZE,		\
+		.bDescriptorType  = USB_DT_ENDPOINT,			\
+		.bEndpointAddress = ENDPOINT,				\
+		.bmAttributes     = 0x02 /* Bulk OUT */,		\
+		.wMaxPacketSize   = USB_MAX_PACKET_SIZE,		\
+		.bInterval        = 0,					\
+	};								\
+	static void CONCAT2(NAME, _ep_tx)   (void) { usb_spi_tx   (&NAME); } \
+	static void CONCAT2(NAME, _ep_rx)   (void) { usb_spi_rx   (&NAME); } \
+	static void CONCAT2(NAME, _ep_reset)(void) { usb_spi_reset(&NAME); } \
+	USB_DECLARE_EP(ENDPOINT,					\
+		       CONCAT2(NAME, _ep_tx),				\
+		       CONCAT2(NAME, _ep_rx),				\
+		       CONCAT2(NAME, _ep_reset));
+
+/*
+ * Check for a new request and process it synchronously, the SPI transaction
+ * will complete before this function returns.
+ *
+ * Returns:
+ *     1: request serviced
+ *     0: no request waiting
+ */
+int usb_spi_service_request(struct usb_spi_config const *config);
+
+/*
+ * These functions are used by the trampoline functions defined above to
+ * connect USB endpoint events with the generic USB GPIO driver.
+ */
+void usb_spi_tx(struct usb_spi_config const *config);
+void usb_spi_rx(struct usb_spi_config const *config);
+void usb_spi_reset(struct usb_spi_config const *config);
+
+#endif /* CHIP_STM32_USB_SPI_H */