On Mon, Jul 04, 2022 at 16:10, "Neil Armstrong" narmstrong@baylibre.com wrote:
This is a preliminary documentation introducing different boot sequences, and notably the recovery mode.
Signed-off-by: Neil Armstrong narmstrong@baylibre.com
Reviewed-by: Mattijs Korpershoek mkorpershoek@baylibre.com
doc/board/amlogic/boot-flow.rst | 147 ++++++++++++++++++++++++++++++++ doc/board/amlogic/index.rst | 1 + 2 files changed, 148 insertions(+) create mode 100644 doc/board/amlogic/boot-flow.rst
diff --git a/doc/board/amlogic/boot-flow.rst b/doc/board/amlogic/boot-flow.rst new file mode 100644 index 0000000000..32943f42db --- /dev/null +++ b/doc/board/amlogic/boot-flow.rst @@ -0,0 +1,147 @@ +.. SPDX-License-Identifier: GPL-2.0+
+Amlogic SoC Boot Flow +=====================
+The Amlogic SoCs has a pre-defined boot sequence in the SoC ROM code.
+Here is the possible boot sources of different SoC families supported by U-Boot:
+GX* & AXG family +----------------
++----------+--------------------+-------+-------+---------------+---------------+ +| | 1 | 2 | 3 | 4 | 5 | ++==========+====================+=======+=======+===============+===============+ +| S905 | POC=0: SPI NOR | eMMC | NAND | SD Card | USB Device | +| S905X | | | | | | +| S905L | | | | | | +| S905W | | | | | | +| S912 | | | | | | ++----------+--------------------+-------+-------+---------------+---------------+ +| S805X | POC=0: SPI NOR | eMMC | NAND | USB Device | - | +| A113D | | | | | | +| A113X | | | | | | ++----------+--------------------+-------+-------+---------------+---------------+
+POC pin: `NAND_CLE`
+Usually boards provides a button to force USB BOOT which disables eMMC clock signal to +bypass eMMC.
+Most of the GX SBCs have removable eMMC modules, in this case removing the eMMC and SDCard +will boot over USB.
+An exception is the lafrite board (aml-s805x-xx) which doesn't have an SDCard and boots +over SPI. The only ways to boot over USB are:
- erase first sectors of SPI NOR flash
- insert an HDMI boot plug forcing boot over USB
+The VIM1 and initial VIM2 boards provides a test point on the eMMC signals to block the +storage from answering and continue to the next boot step.
+The USB Device boot uses the first USB interface, on some boards this port is only +available on an USB-A type connector, and needs an special Type-A to Type-A cable +to communicate with the BootROM.
+G12* & SM1 family +-----------------
++-------+-------+-------+---------------+---------------+---------------+---------------+ +| POC0 | POC1 | POC2 | 1 | 2 | 3 | 4 | ++=======+=======+=======+===============+===============+===============+===============+ +| 0 | 0 | 0 | USB Device | SPI NOR | NAND/eMMC | SDCard | ++-------+-------+-------+---------------+---------------+---------------+---------------+ +| 0 | 0 | 1 | USB Device | NAND/eMMC | SDCard | - | ++-------+-------+-------+---------------+---------------+---------------+---------------+ +| 0 | 1 | 0 | SPI NOR | NAND/eMMC | SDCard | USB Device | ++-------+-------+-------+---------------+---------------+---------------+---------------+ +| 0 | 1 | 1 | SPI NAND | NAND/eMMC | USB Device | - | ++-------+-------+-------+---------------+---------------+---------------+---------------+ +| 1 | 0 | 0 | USB Device | SPI NOR | NAND/eMMC | SDCard | ++-------+-------+-------+---------------+---------------+---------------+---------------+ +| 1 | 0 | 1 | USB Device | NAND/eMMC | SDCard | - | ++-------+-------+-------+---------------+---------------+---------------+---------------+ +| 1 | 1 | 0 | SPI NOR | NAND/eMMC | SDCard | USB Device | ++-------+-------+-------+---------------+---------------+---------------+---------------+ +| 1 | 1 | 1 | NAND/eMMC | SDCard | USB Device | - | ++-------+-------+-------+---------------+---------------+---------------+---------------+
+The last is the normal default boot on production devices.
- POC0 pin: `BOOT_4` (0 and all other 1 means SPI NAND boot first)
- POC1 pin: `BOOT_5` (0 and all other 1 means USB Device boot first
- POC2 pin: `BOOT_6` (0 and all other 1 means SPI NOR boot first)
+Usually boards provides a button to force USB BOOT which lowers `BOOT_5` to 0.
+Some boards provides a test point on the eMMC or SPI NOR clock signals to block the +storage from answering and continue to the next boot step.
+The Khadas VIM3 boards embeds a microcontroller which sets POC signals depending +on it's configuration or a specific key press sequence to either boot from SPI NOR +or eMMC then SDCard, or boot as USB Device.
+The Odroid-N2(+) has a switch to select SPI NOR or eMMC boot.
+Boot Modes +----------
- SDCard
+The BootROM fetches the first SDCard sectors in one sequence, then checks the content +of the data.
+The BootROM expects finding the FIP binary are sector 1, 512 bytes offset from the start.
- eMMC
+The BootROM fetches the first sectors in one sequence, first on the main partition, +and then on the Boot0 followed by Boot1 HW partitions.
+After each read, the BootROM checks the data and looks the next partition if it fails.
+The BootROM expects finding the FIP binary are sector 1, 512 bytes offset from the start.
- SPI NOR
+The BootROM fetches the first SPI NOR sectors in one sequence, then checks the content +of the data.
+The BootROM expects finding the FIP binary are sector 1, 512 bytes offset from the start.
- NAND & SPI NAND
+Those modes are not widely used in open platforms, thus no details are available.
- USB Device
+The BootROM setups the USB Gadget interface to serve a custom USB protocols with the +USB ID 1b8e:c003.
+This protocol is also implemented in the Amlogic Vendor U-Boot.
+The `update` utility provided by Amlogic is designed to use this protocol.
+The https://github.com/superna9999/pyamlboot open-source utility also implements this +protocol and can load U-Boot in memory in order to start the SoC without any attached +storage or to recover from a failed storage/flash tentative.
+HDMI Recovery +-------------
+The BootROM also briefly reads 8 bytes at address I2C 0x52 offset 0xf8 (248) on the +HDMI DDC bus.
+If the content is `boot@USB` it will force USB boot mode, if the content is `boot@SDC` +it will force SDCard boot mode.
+If USB Device doesn't enumerate or SD Card boot step doesn't work, it will continue the +boot steps.
+Special boot dongles can be built by connecting a 256bytes EEPROM set to answer on +address 0x52, and program `boot@USB` or `boot@SDC` at offset 0xf8 (248).
+Note: if the SoC was booted with USB Device forced at first step, it will keep the boot +order on a warm reboot, only a cold reboot (remove power) will reset the boot order. diff --git a/doc/board/amlogic/index.rst b/doc/board/amlogic/index.rst index 9c7fadf2c0..8b9f1e2e1d 100644 --- a/doc/board/amlogic/index.rst +++ b/doc/board/amlogic/index.rst @@ -81,6 +81,7 @@ Boot Documentation :maxdepth: 1
pre-generated-fip
- boot-flow
Board Documentation
-- 2.25.1
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