Re: [edk2-platforms][PATCH 2/2] RPi: update Pi3 and Pi4 readmes with correct info on FDT handling

["Pete Batard" <pete@akeo.ie>]

On 2020.04.30 20:19, Andrei Warkentin wrote:
> Now that Pi 3 FDT handling is fixed, let's update the docs. Furthermore,
> let's simplify - be proscriptive about the minimal supported
> config.txt configuration. Also, fix some factual mistakes:
> - device_tree= override is not mandatory when device_tree_address= is used.
>    Not using it means start.elf can chose the right one for the variant.
> - device_tree= override is not mandatory for dtoverlay use.
> 
> Signed-off-by: Andrei Warkentin <andrey.warkentin@gmail.com>
> ---
>   Platform/RaspberryPi/RPi3/Readme.md | 38 +++++++++++++-------
>   Platform/RaspberryPi/RPi4/Readme.md | 24 +++++++------
>   2 files changed, 39 insertions(+), 23 deletions(-)
> 
> diff --git a/Platform/RaspberryPi/RPi3/Readme.md b/Platform/RaspberryPi/RPi3/Readme.md
> index f5d25b50..f19d59d8 100644
> --- a/Platform/RaspberryPi/RPi3/Readme.md
> +++ b/Platform/RaspberryPi/RPi3/Readme.md
> @@ -56,23 +56,30 @@ Build instructions from the top level edk2-platforms Readme.md apply.
>   1. Format a uSD card as FAT32
>   2. Copy the generated `RPI_EFI.fd` firmware onto the partition
>   3. Download and copy the following files from https://github.com/raspberrypi/firmware/tree/master/boot
> +  - `bcm2710-rpi-3-b.dtb` (for Pi 3B)
> +  - `bcm2710-rpi-3-b-plus.dtb (for Pi 3B+)

Missing closing ` after .dtb.

Rather than re-send a new patch, could the maintainer please add it when 
committing?

> +  - `bcm2710-rpi-2-b.dtb` (for Pi 2B v1.2)
> +  - `bcm2710-rpi-cm3.dtb` (for Pi CM3)
>     - `bootcode.bin`
>     - `fixup.dat`
>     - `start.elf`
> +  - `overlays/miniuart-bt.dtbo` or `overlays/disable-bt.dtbo` (Optional)
>   4. Create a `config.txt` with the following content:
>     ```
>     arm_control=0x200
>     enable_uart=1
>     armstub=RPI_EFI.fd
> -  disable_commandline_tags=1
> +  disable_commandline_tags=2
> +  device_tree_address=0x1f0000
> +  device_tree_end=0x200000
>     ```
> -  Additionally, if you want to use PL011 instead of the miniUART, you can add the lines:
> +  If you want to use PL011 instead of the miniUART on your Pi 3B/3B+, you can add the lines:
>     ```
> -  device_tree_address=0x10000
> -  device_tree_end=0x20000
> -  device_tree=bcm2710-rpi-3-b[-plus].dtb
>     dtoverlay=miniuart-bt
>     ```
> +  Note: doing so requires `miniuart-bt.dbto` to have been copied into an `overlays/`
> +  directory on the uSD card. Alternatively, you may use `disable-bt` instead of
> + `miniuart-bt` if you don't require Bluetooth.
>   5. Insert the uSD card and power up the Pi.
>   
>   Note that if you have a model 3+ or a model 3 where you enabled USB boot through OTP
> @@ -92,21 +99,26 @@ in the `TrustedFirmware/` directory from `edk2-non-osi`.
>   
>   ## Custom Device Tree
>   
> -The default Device Tree included in the firmware is the one for a Raspberry Pi 3 Model B (not B+).
> -If you want to use a different Device Tree, to boot a Pi 3 Model B+ for instance (for which a
> -DTB is also provided under `DeviceTree/`), you should copy the relevant `.dtb` into the root of
> +By default, UEFI will use the device tree loaded by the VideoCore firmware. This
> +depends on the model/variant, and relies on the presence on specific files on your boot media.
> +E.g.:
> + - `bcm2710-rpi-3-b.dtb` (for Pi 3B)
> + - `bcm2710-rpi-3-b-plus.dtb (for Pi 3B+)

Same as above (Missing closing ` after .dtb).

> + - `bcm2710-rpi-2-b.dtb` (for Pi 2B v1.2)
> + - `bcm2710-rpi-cm3.dtb` (for Pi CM3)
> +
> +You can override the DTB and provide a custom one. Copy the relevant `.dtb` into the root of
>   the SD or USB, and then edit your `config.txt` so that it looks like:
>   
>   ```
>   (...)
>   disable_commandline_tags=2
> -device_tree_address=0x10000
> -device_tree_end=0x20000
> -device_tree=bcm2710-rpi-3-b-plus.dtb
> +device_tree_address=0x1f0000
> +device_tree_end=0x200000
> +device_tree=your_fdt_file.dtb
>   ```
>   
> -Note: the address range **must** be `[0x10000:0x20000]`.
> -`dtoverlay` and `dtparam` parameters are also supported **when** providing a Device Tree`.
> +Note: the address range **must** be `[0x1f0000:0x200000]`. `dtoverlay` and `dtparam` parameters are also supported.
>   
>   ## Custom `bootargs`
>   
> diff --git a/Platform/RaspberryPi/RPi4/Readme.md b/Platform/RaspberryPi/RPi4/Readme.md
> index 17d02e9e..62a63c4c 100644
> --- a/Platform/RaspberryPi/RPi4/Readme.md
> +++ b/Platform/RaspberryPi/RPi4/Readme.md
> @@ -54,18 +54,17 @@ Build instructions from the top level edk2-platforms Readme.md apply.
>       enable_uart=1
>       enable_gic=1
>       armstub=RPI_EFI.fd
> -    disable_commandline_tags=1
> +    disable_commandline_tags=2
> +    device_tree_address=0x1f0000
> +    device_tree_end=0x200000
>       ```
>       Additionally, if you want to use PL011 instead of the miniUART, you can add the lines:
>       ```
> -    device_tree_address=0x1f0000
> -    device_tree_end=0x200000
> -    device_tree=bcm2711-rpi-4-b.dtb
>       dtoverlay=miniuart-bt
>       ```
> -    Note that doing so requires `miniuart-bt.dbto` to have been copied into an `overlays/`
> +    Note: doing so requires `miniuart-bt.dbto` to have been copied into an `overlays/`
>       directory on the uSD card. Alternatively, you may use `disable-bt` instead of
> -    `miniuart-bt` if you don't require BlueTooth.
> +    `miniuart-bt` if you don't require Bluetooth.
>   5. Insert the uSD card and power up the Pi.
>   
>   # Notes
> @@ -81,18 +80,23 @@ in the `TrustedFirmware/` directory from `edk2-non-osi`.
>   
>   ## Device Tree
>   
> -You can pass a custom Device Tree and overlays using the following:
> +By default, UEFI will use the device tree loaded by the VideoCore firmware. This
> +depends on the model/variant, and relies on the presence on specific files on your boot media.
> +E.g.:
> + - `bcm2711-rpi-4-b.dtb` (for Pi 4B)
> +
> +You can override the DTB and provide a custom one. Copy the relevant `.dtb` into the root of
> +the SD or USB, and then edit your `config.txt` so that it looks like:
>   
>   ```
>   (...)
>   disable_commandline_tags=2
>   device_tree_address=0x1f0000
>   device_tree_end=0x200000
> -device_tree=bcm2711-rpi-4-b.dtb
> +device_tree=your_fdt_file.dtb
>   ```
>   
> -Note: the address range **must** be `[0x1f0000:0x200000]`.
> -`dtoverlay` and `dtparam` parameters are also supported **when** providing a Device Tree`.
> +Note: the address range **must** be `[0x1f0000:0x200000]`. `dtoverlay` and `dtparam` parameters are also supported.
>   
>   ## Custom `bootargs`
>   
> 

With the above 2 typos fixed,
Reviewed-by: Pete Batard <pete@akeo.ie>