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diff --git a/board/servo_micro/ccd.md b/board/servo_micro/ccd.md deleted file mode 100644 index 267da66776..0000000000 --- a/board/servo_micro/ccd.md +++ /dev/null @@ -1,168 +0,0 @@ -<!-- - Copyright 2018 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. ---> - -# Case-Closed Debug in Chromebooks and Servo Micro - -The Servo debug/test-automation connector has been required on all chromebooks. -It has proved essential to performing the required testing to meet the six week -OS release cycle, for bringing up new systems and qualifying new components. In -newer form-factors it is becoming hard to fit the Servo connector (and related -flex) and in some designs the thermal solution stops working when the connector -is used. The secure Case-Closed Debugging solution provides the same -capabilities and can take advantage of the Debug Mode detection available on the -USB-C connector. This application note gives an overview of Case-Closed Debug -(CCD) but does not address the related security issues. - -## Introduction to Case-Closed Debug - -Case-Closed Debug provides the same set of features as are available on the -Servo connector: - -* Access to console UART connections to AP, EC and on some systems a third MCU -* Ability to reprogram firmware/BIOS SPI flash used by the AP -* Ability to reprogram SPI flash used by the EC or use a firmware update mode - to reprogram the internal flash on the EC (using UART or I2C) -* GPIOs for holding the EC (and thus entire system) or AP in reset -* Act as master on a debug I2C that is primarily used for power measurements. - This bus normally contains INA voltage/current monitors and temperature - monitors that will not be populated on final MP systems. -* JTAG/SWD could be provided but has not been implemented on any existing - system. - -When the Servo connector is used these interfaces are presented on well defined -pins of the board-to-board connector and a flex is used to attach to the -external Servo controller. The height needed for the mated board-to-board -connector is not available in newer slim designs, and the disruption caused by -the flex may interfere with thermal solutions. In a system using Case-Closed -Debug the interfaces are gathered by a part on the board into a single USB -interface that can come out of the system on an existing connector. In -particular, the USB-C connector has two SideBand Use pins (SBU1, SBU2) that can -be used for the debug USB while the main link on the connector continues to be -available. (The SBU pins are also used by some Alternate Modes, so the connector -cannot be used for video out at the same time as debugging.) - -## Servo Micro: Using CCD with existing boards - -The Servo Micro implements the CCD functions in a way that can connect to -existing boards and thus can also serve as an easy introduction to the CCD -implementation. The debug USB interface is expanded by a STM32F072 into an -existing Servo flex connector that can be plugged into the target board. - - - -The Servo Micro includes the voltage level buffering between the microcontroller -and the device under test (DUT), making use of the DUT supplied reference -voltages. To allow use with all the existing designs a third UART (not on the -original Servo connector, but on some designs) can be connected to either the -JTAG pins or the SPI pins. It is capable of providing the SPI flash supply -voltages. - -The schematics for Servo Micro are available -[as a pdf](servo_micro_sch_20180404.pdf). - -Servo Micro has a USB micro-B connector and acts as a USB device. - -Schematic sheet 2 shows the STM32 powered from the uB connector. The UART3 pins -can also be used as GPIO pins when driving the JTAG interface. As a useful but -non-compliant hack if the ID pin on the uB is low then Q4 will force the STM32 -to boot in programming mode. This allows initial programming of the part with -USB DFU using an illegal USB-A plug to USB-A plug cable and a USB-A receptacle -to uB plug adapter. Alternatively the initial programming can be done using a -UART connection on CN2. - -Schematic sheet 3 shows the I2C GPIO expander and the buffers for JTAG/SWD. The -buffers adapt to the voltage needed on the DUT that is provided on -`PPDUT_JTAG_VREF`. In the SWD case the TDI becomes the bidirectional SWDIO but -the STM32 continues to use a discrete input and output pin. The DUT signal is -received through U55 and a selection made with U1 to determine if to forward TDO -from the DUT or the TDI/SWDIO. Because of the shared pins on the STM32 the JTAG -interface can alternatively be used to connect UART3 to the DUT for a few -chromebook models. - -Schematic sheet 4 shows the buffers for the SPI interfaces. Again the -`PPDUT_SPIn_VREF` sets the voltage level required from the DUT. However, I61 and -I62 (which are expanded on sheets 7 and 8) allow the Servo Micro to supply 3.3V -or 1.8V for cases where the DUT does not provide the reference (care is needed -to select the correct voltage for the given DUT). Only one of the SPI interfaces -can be used at any time, so the buffers are also used to select which connects -to the STM32 SPI pins. Certain chromebook models connect the UART3 in place of -SPI1 which is enabled using U5 to select between the STM32 UART3 (TX,RX) and SPI -(CLK, MISO). - -Schematic sheet 5 shows the buffers for the UART interfaces. The -`PPDUT_UARTn_VREF` sets the voltage level required from the DUT. - -Schematic sheet 6 shows the board-to-board connector that mates with the servo -connector on the DUT. - -Schematic sheets 7 and 8 are the expansion of blocks I61 and I62 on sheet 4. The -load switches are carefully selected to have reverse blocking (protecting -against a DUT providing a voltage or both being enabled). - -The code for the STM32 in Servo Micro is open source as the -[`servo_micro`](../../board/servo_micro) board in the -[Chromium EC codebase](https://chromium.googlesource.com/chromiumos/platform/ec/). -Essentially it is a USB device that provides the standard control endpoint and 7 -function endpoints defined in [`board.h`](board.h). - -<!-- does not work in emacs/markdown preview but should in gitlies --> - -```c -#define USB_EP_USART4_STREAM 1 -#define USB_EP_UPDATE 2 -#define USB_EP_SPI 3 -#define USB_EP_CONSOLE 4 -#define USB_EP_I2C 5 -#define USB_EP_USART3_STREAM 6 -#define USB_EP_USART2_STREAM 7 -``` - -The USART endpoints use the simple `GOOGLE_SERIAL` vendor class to connect the -STM32 UARTs. The CONSOLE endpoint also uses `GOOGLE_STREAM` to connect to the -console of the code running on the STM32. `GOOGLE_STREAM` provides simple byte -streams on the IN and OUT of the endpoint and host support is included in the -standard Linux `drivers/usb/serial/usb-serial-simple.c` - -The SPI endpoint is described in -[`chip/stm32/usb_spi.h`](../../chip/stm32/usb_spi.h) and provides a simple -connection to the SPI port. The host support is provided as a -[driver in flashrom](https://chromium.googlesource.com/chromiumos/third_party/flashrom/+/HEAD/raiden_debug_spi.c). - -The I2C endpoint is described in [`include/usb_i2c.h`](../../include/usb_i2c.h) -and provides a simple connection to the I2C bus. The host support is provided in -the -[hdctools servo support](https://chromium.googlesource.com/chromiumos/third_party/hdctools/+/HEAD/servo/stm32i2c.py). - -The GPIO endpoint is cryptically described in -[`chip/stm32/usb_gpio.h`](../../chip/stm32/usb_gpio.h) and provides simple -access to set/clear and read the GPIO pins. The host support is provided in the -[hdctools servo support](https://chromium.googlesource.com/chromiumos/third_party/hdctools/+/HEAD/servo/stm32gpio.py). - -The UPDATE endpoint is not part of CCD. It provides a method for updating the -STM32 without needing the special boot modes. This uses the -[Chromium EC update over USB](../../docs/usb_updater.md) method. The STM32 runs -the code in [`common/usb_update.c`](../../common/usb_update.c). The host side -code is in -[`extra/usb_updater/usb_updater2.c`](../../extra/usb_updater/usb_updater2.c) and -the [`extra/usb_updater`](../../extra/usb_updater/) directory contains -additional scripts. - -## Using CCD on new designs - -New chromebook designs implement the CCD in a similar way to Servo Micro. There -are two changes to the Servo Micro: - -* The USB microB connector is replaced with the USB connection being carried - on the SBU pins of one of the devices USB-C ports. This will only be - activated when the USB-C port detects a debug accessory or a debug alternate - mode is entered. Use of the debug connection precludes use of the Display - Port alternate mode (which also uses the SBU pins) but allows full USB3 and - USB2 functions including both host and gadget mode. -* The system security chip will normally lock out debug access. Using secure - transactions, user authorization and proof of user physical presence it can - unlock various degrees of debug access. - -The full details are part of the Cr50 firmware specification. |