apache · acassis · Oct 28, 2025 · Sep 21, 2025 · Oct 27, 2025
@@ -2,7 +2,7 @@
 Raspberry Pi 4B
 ===============
 
-.. tags:: chip:bcm2711, experimental
+.. tags:: arch:arm64, chip:bcm2711, vendor:raspberry-pi, experimental
 
 .. warning::
 
@@ -13,17 +13,6 @@ Raspberry Pi 4B
    found an issue with any of the implementation! See :doc:`the contributing
    guidelines </contributing/index>`.
 
-.. warning::
-
-   The SPI driver implemented for the :doc:`BCM2711 <../../index>` has only been
-   tested on SPI0. It appears that even using the special `overlays
-   <https://github.com/raspberrypi/linux/blob/stable/arch/arm/boot/dts/overlays/README>`_
-   for the device tree passed to the proprietary firmware does not properly
-   initialize the remaining SPI interfaces, and thus they have not been working
-   properly. More effort is required to reverse engineer the magic incantations
-   required to initialize these interfaces, at which point it is assumed that
-   the driver implementation should extend to SPI3-6.
-
 The `Raspberry Pi 4B <https://www.raspberrypi.com/products/raspberry-pi-4-model-b/specifications/>`_ is an ARM64
 hobbyist board created by Raspberry Pi.
 
@@ -33,7 +22,7 @@ hobbyist board created by Raspberry Pi.
    :alt: Raspberry Pi 4B board
 
 Features
-=========
+========
 
 - Broadcom BCM2711 @1.8GHz
 - 1, 2, 4 and 8GB LPDDR4-3200 SDRAM models
@@ -48,8 +37,50 @@ Features
 - 4-pole stereo audio and composite video port
 - Micro SD card slot
 
-ARM64 Toolchain
-===============
+Board Peripheral Support
+========================
+
+SMP is currently unsupported. To see support for chip peripherals (I2C, SPI,
+UART, etc), see the :doc:`BCM2711 page <../../index>`
+
+NuttX for the Raspberry Pi 4 supports these on-board peripherals:
+
+======================== =======
+Peripheral               Support
+======================== =======
+AV port                  No
+HDMI                     No
+WiFi                     No
+Ethernet                 No
+USB 3.0                  No
+USB 2.0                  No
+Bluetooth                No
+microSD card             Yes (see notes in BCM2711 page)
+======================== =======
+
+Buttons and LEDs
+================
+
+The board has two LEDs:
+
+* SD card activity (green)
+* Power (red)
+
+These LEDs are controlled by proprietary firmware at the beginning of the boot
+process. Afterwards, NuttX controls them with the ``autoleds`` framework. At
+this time:
+
+* Red LED is solid for assertion failure, or blinks on panic
+* Green LED is solid when NuttX has started
+
+Power Supply
+============
+
+The board can be supplied power either through the USB-C connection (5V) or via
+the 5V power input pin.
+
+Installation
+============
 
 Before building NuttX for the Raspberry Pi 4B, download the ARM64 Toolchain for
 **AArch64 Bare-Metal Target** ``aarch64-none-elf`` from
@@ -70,21 +101,7 @@ Check the ARM64 Toolchain:
 
     $ aarch64-none-elf-gcc -v
 
-Building
-========
-
-To build NuttX for the Raspberry Pi 4B, :doc:`install the prerequisites </quickstart/install>` and :doc:`clone the git
-repositories </quickstart/install>` for ``nuttx`` and ``apps``.
-
-Configure the NuttX project to use the Raspberry Pi 4B and build it (this example uses the ``nsh`` configuration).
-
-.. code:: console
-
-    $ cd nutxx
-    $ tools/configure.sh raspberrypi-4b:nsh
-    $ make
-
-Booting
+Flashing
 ========
 
 In order to boot NuttX on the Raspberry Pi 4B, you will need to have a formatted micro SD card. The SD card should
@@ -152,26 +169,38 @@ appear onscreen:
     NuttShell (NSH) NuttX-12.6.0-RC0
     nsh> uname -a
     NuttX 12.6.0-RC0 c4f3a42131-dirty Aug  6 2024 21:17:01 arm64 raspberrypi-4b
-    nsh> 
+    nsh>
 
-Board Peripheral Support
-========================
+Configurations
+==============
 
-SMP is currently unsupported.
+You can configure NuttX for the Raspberry Pi 4B using the following command:
 
-To see support for general chip peripherals (I2C, SPI, UART, etc), see the
-:doc:`BCM2711 page <../../index>`
+.. code:: console
 
-NuttX for the Raspberry Pi 4 supports these on-board peripherals:
+   $ ./tools/configure.sh raspberrypi-4b:<config>
 
-======================== =======
-Peripheral               Support
-======================== =======
-AV port                  No
-HDMI                     No
-WiFi                     No
-Ethernet                 No
-USB 3.0                  No
-USB 2.0                  No
-Bluetooth                No
-======================== =======
+Where ``<config>`` is one of the configurations listed below.
+
+nsh
+---
+
+A simple configuration with NSH on the Mini-UART console, accessible using a TTL
+cable connected to GPIO 14 & 15.
+
+sd
+--
+
+Configuration which supports the microSD card peripheral on EMMC2. At boot time,
+the microSD card is identified and the boot partition is mounted as a FAT file
+system to ``/sd``. It can be written to and read from.
+
+.. warning::
+
+   There is some instability with the microSD card functionality. Please see
+   :doc:`/platforms/arm64/bcm2711/index` for more information.
+
+.. note::
+
+   This configuration enables BSD components since the :doc:`sdstress
+   </applications/testing/sd_stress/index>` application is BSD licensed.
@@ -2,7 +2,7 @@
 BCM2711
 =======
 
-.. tags:: chip:bcm2711, experimental
+.. tags:: arch:arm64, chip:bcm2711, vendor:broadcom, experimental
 
 .. warning::
 
@@ -26,14 +26,50 @@ Supported Peripherals
 ======================== =======
 Peripheral               Support
 ======================== =======
-I2C                      Full interrupt-based support, all interfaces work and tested.
+I2C                      Full interrupt-based support. No 10b addressing.
 UART                     Mini UART yes, PL011 no
 GPIO                     Partial
+MAILBOX                  Partial (polled method, only commands used by firmware are implemented)
+EMMC2                    Interrupt-based support, no DMA.
+EMMC                     Supported alongside EMMC2 in theory, but untested.
 PWM                      No
 SPI                      Interrupt-based driver (no DMA) for all SPI except 1 & 2 (auxiliary)
 PCM                      No
 ======================== =======
 
+.. warning::
+
+   The SPI driver implemented for the :doc:`BCM2711 <../../index>` has only been
+   tested on SPI0. It appears that even using the special `overlays
+   <https://github.com/raspberrypi/linux/blob/stable/arch/arm/boot/dts/overlays/README>`_
+   for the device tree passed to the proprietary firmware does not properly
+   initialize the remaining SPI interfaces, and thus they have not been working
+   properly. More effort is required to reverse engineer the magic incantations
+   required to initialize these interfaces, at which point it is assumed that
+   the driver implementation should extend to SPI3-6.
+
+.. warning::
+
+   The EMMC2 peripheral connects to the microSD card slot on the :doc:`Raspberry
+   Pi 4B </platforms/arm64/bcm2711/boards/raspberrypi-4b/index>`. Currently, it
+   has been tested using a 32GB Samsung microSD card and it has passed testing
+   with that. The only quirks are:
+
+   * No card insertion/removal interrupts work, so hotswapping isn't possible
+   * The :doc:`sdstress </applications/testing/sd_stress/index>` example works
+     unless the 'number of bytes' option is greater than 1023. I suspect this is
+     something to do with the FIFO depth being only 1023 bytes.
+
+   However, the 64GB microSD card exhibits very strange behaviour. There are
+   often data CRC errors that prevent the boot filesystem from mounting. When
+   that somehow passes (intermittent), running ``ls`` on the filesystem repeatedly
+   sometimes causes certain files to disappear from the listing (they are not
+   deleted and appear again on next boot), or causes their filenames to be shown
+   in all caps. Writing to the card with ``echo`` often fails with data CRC
+   error or timeout, and then the card is buggy for the remainder of the
+   session. **It is not recommended to use 64GB cards with this implementation
+   for the time being.**
+
 Supported Boards
 ================
 

@@ -122,6 +122,7 @@ config ARCH_CHIP_BCM2711
 	select ARCH_HAVE_MULTICPU
 	select ARCH_USE_MMU # Required for up_testset
 	select ARMV8A_HAVE_GICv2
+	select ARCH_HAVE_SDIO
 	---help---
 		Broadcom BCM2711 quad-core ARM Cortex A72
 

@@ -36,9 +36,15 @@ if(CONFIG_BCM2711_I2C)
 endif()
 
 # SPI interfaces
-#
+
 if(CONFIG_BCM2711_SPI)
   list(APPEND SRCS bcm2711_spi.c)
 endif()
 
+# EMMC interfaces
+
+if(CONFIG_BCM2711_EMMC)
+  list(APPEND SRCS bcm2711_sdio.c)
+endif()
+
 target_sources(arch PRIVATE ${SRCS})
@@ -281,6 +281,54 @@ config BCM2711_SPI6
 
 endif # BCM2711_SPI
 
+#####################################################################
+# SDMMC Configuration
+#####################################################################
+
+config BCM2711_EMMC
+	bool "EMMC support"
+	select MMCSD
+	select MMCSD_SDIO
+	select SDIO_BLOCKSETUP
+	depends on EXPERIMENTAL
+	default n
+	---help---
+		Enables support for EMMC interfaces.
+
+if BCM2711_EMMC
+
+config BCM2711_EMMC1
+	bool "EMMC1 interface support"
+	depends on BCM2711_EMMC
+	default n
+	---help---
+		Enables support for the EMMC1 interface.
+
+config BCM2711_EMMC1_XFERSPEED
+	int "EMMC1 transfer speed (Hz)"
+	depends on BCM2711_EMMC1
+	range 25000000 208000000
+	default 25000000
+	---help---
+		The transfer speed in Hz to use for EMMC1 transfers.
+
+config BCM2711_EMMC2
+	bool "EMMC2 interface support"
+	depends on BCM2711_EMMC
+	default n
+	---help---
+		Enables support for the EMMC2 interface.
+
+config BCM2711_EMMC2_XFERSPEED
+	int "EMMC2 transfer speed (Hz)"
+	depends on BCM2711_EMMC2
+	range 25000000 208000000
+	default 25000000
+	---help---
+		The transfer speed in Hz to use for EMMC2 transfers.
+
+endif # BCM2711_EMMC
+
 endmenu # Broadcom BCM2711 Peripheral Selection
 
 endif # ARCH_CHIP_BCM2711
diff --git a/arch/arm64/src/bcm2711/Make.defs b/arch/arm64/src/bcm2711/Make.defs
@@ -41,7 +41,13 @@ CHIP_CSRCS += bcm2711_i2c.c
 endif
 
 # SPI interfaces
-#
+
 ifeq ($(CONFIG_BCM2711_SPI),y)
 CHIP_CSRCS += bcm2711_spi.c
 endif
+
+# EMMC interfaces
+
+ifeq ($(CONFIG_BCM2711_EMMC),y)
+CHIP_CSRCS += bcm2711_sdio.c
+endif