Platform/RaspberryPi: Documentation updates

This cleans up the (related) Readme.md files for both platforms.

- The RPi3 target also supports the 3A+, so let's document it.
(The 3A+ lacks the ethernet port and has less RAM)

- Clarify RPi3 is for BCM2837-based variants, while RPi4 is
for the BCM2711-based variants.

- v1.2 (not older) actually uses the same BCM2837 SoC as
Pi 3, and is thus a 64-bit device that this firmware
easily supports as a minor variant of the Pi 3.

The difference from Pi 3 is choice of UART (PL011), no WiFi,
no BT and slower clock due to thermal problems caused by
older board design.

Signed-off-by: Andrei Warkentin <andrey.warkentin@gmail.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@arm.com>

1 files changed, 33 insertions, 16 deletions

diff --git a/Platform/RaspberryPi/RPi3/Readme.md b/Platform/RaspberryPi/RPi3/Readme.md
index 05f498ee..f5d25b50 100644
--- a/Platform/RaspberryPi/RPi3/Readme.md
+++ b/Platform/RaspberryPi/RPi3/Readme.md
@@ -1,19 +1,33 @@
-Raspberry Pi Platform

-=====================

+Raspberry Pi 3 Platform

+=======================

 

 # Summary

 

-This is a port of 64-bit Tiano Core UEFI firmware for the Raspberry Pi 3/3B+ platforms,

-based on [Ard Bisheuvel's 64-bit](http://www.workofard.com/2017/02/uefi-on-the-pi/)

+This is a port of 64-bit Tiano Core UEFI firmware for the Raspberry Pi 3B (and related)

+platforms, based on [Ard Biesheuvel's 64-bit](http://www.workofard.com/2017/02/uefi-on-the-pi/)

 and [Microsoft's 32-bit](https://github.com/ms-iot/RPi-UEFI/tree/ms-iot/Pi3BoardPkg)

 implementations, as maintained by [Andrei Warkentin](https://github.com/andreiw/RaspberryPiPkg).

 

-This is meant as a generally useful 64-bit ATF + UEFI implementation for the Raspberry

-Pi 3/3B+ which should be good enough for most kind of UEFI development, as well as for

-running consummer Operating Systems in such as Linux or Windows.

+This is meant as a generally useful 64-bit ATF + UEFI implementation for Raspberry Pi

+variants based on the BCM2837 SoC, which should be good enough for most kind of UEFI development,

+as well as for running consummer Operating Systems in such as Linux, Windows or the BSDs.

 

 Raspberry Pi is a trademark of the [Raspberry Pi Foundation](http://www.raspberrypi.org).

 

+# Hardware Supported

+

+The RPi3 target supports Pi revisions based on the BCM2837 SoC:

+- Raspberry Pi 2B v1.2 (older versions are *not* compatible)

+- Raspberry Pi 3A+

+- Raspberry Pi 3B

+- Raspberry Pi 3B+

+- Raspberry Pi CM3

+

+Note: a CM3L, lacking eMMC and thus similar to the 3B, will probably work as well, but just

+has not been tested.

+

+Please see the RPi4 target for BCM2711-based variants, such as the Raspberry Pi 4B.

+

 # Status

 

 This firmware, that has been validated to compile against the current

@@ -138,27 +152,28 @@ This should allow you to set whatever date/time you want using the Shell date an
 time commands. While in UEFI or HLOS, the time will tick forward.

 `RtcEpochSeconds` is not updated on reboots.

 

-## uSD

+## uSD (and eMMC for CM3)

 

-UEFI supports both the Arasan SDHCI and the Broadcom SDHost controllers to access the uSD slot.

-You can use either. The other controller gets routed to the SDIO card. The choice made will

+UEFI supports both the Arasan SDHCI and the Broadcom SDHost controllers to access the flash

+media (eMMC on CM3, and uSD slot on everything else). You can use either. The other controller

+gets routed to the SDIO WiFi card (N/A to models without WiFi). The choice made will

 impact ACPI OSes booted (e.g. Windows 10). Arasan, being an SDIO controller, is usually used

-with the WiFi adapter where available. SDHost cannot be used with SDIO. In UEFI setup screen:

+with the WiFi adapter (where available). SDHost cannot be used with SDIO. In UEFI setup screen:

 - go to `Device Manager`

 - go to `Raspberry Pi Configuration`

-- go to `Chipset`

-- configure `Boot uSD Routing`

+- go to `SD/MMC Configuration`

+- configure `uSD/eMMC Routing`

 

 Known issues:

 - Arasan HS/4bit support is missing.

-- No 8 bit mode support for (e)MMC (irrelevant for the Pi 3).

+- No 8 bit mode support for (e)MMC (slow UEFI file I/O on CM3).

 - Hacky (e)MMC support (no HS).

 - No card removal/replacement detection, tons of timeouts and slow down during boot without an uSD card present.

 

 ## USB

 

 - USB1 BBB mass storage devices untested (USB2 and USB3 devices are fine).

-- USB1 CBI mass storage devices don't work (e.g. HP FD-05PUB floppy).

+- Some USB1 CBI (e.g. UFI floppy) mass storage devices may not work.

 

 ## ACPI

 

@@ -172,4 +187,6 @@ install a kernel that relies on Device Tree rather than ACPI.
 ## Missing Functionality

 

 - Network booting via onboard NIC.

-- Ability to switch UART use to PL011.

+- SPCR hardcodes UART type to miniUART, and thus will not expose correct

+  (PL011) UART on CM3 and Pi2B or if DT overlays to switch UART are used

+  on Pi 3B/3B+/3A+.