Accessing MMC/SD card storage on Raspberry Pi

["Tomaž Šolc" <tomaz.solc@klevio.com>]

Dear all,

I've been trying to set up Barebox on a Raspberry Pi Compute Module 3. 
After some small fixes (see below) I've got 2019.01.0 to boot to a 
command line on the serial port. However I can't get access to the MMC 
storage to load a kernel ("no /dev/disk0.0. using default env")

Looking at the source, it seems that a "bcm2835-sdhost" driver is 
missing (bcm2835_mci seems to only be used for the other SDIO interface 
towards the wireless interface on other R. Pis) Is MMC storage indeed 
not supported on R. Pi at the moment or am I missing something?

Thanks
Tomaž




A list of things I needed to do to boot on R. Pi CM3, just in case it's 
useful for someone else:

Add board rev 10 to rpi_models_new_scheme in rpi-common.c

Note that rpi_model_init() segfaults if board rev is not found in the 
list because model remains NULL.

Use device tree in bcm2837-rpi-cm3-io3.dts. Most importantly, this 
disables the bcm2835_mci driver, which otherwise hangs on boot (I'm 
guessing unsuccessfully trying to init the empty SDIO bus where there 
would otherwise be a wireless interface on R.Pi 3.).


diff -ru a/arch/arm/boards/raspberry-pi/rpi-common.c 
b/arch/arm/boards/raspberry-pi/rpi-common.c
--- a/arch/arm/boards/raspberry-pi/rpi-common.c 2019-02-07 
15:37:49.181360164 +0100
+++ b/arch/arm/boards/raspberry-pi/rpi-common.c 2019-02-11 
08:48:36.000000000 +0100
@@ -175,6 +175,7 @@
         RPI_MODEL(0, "Unknown model", NULL),
         RPI_MODEL(BCM2836_BOARD_REV_2_B, "2 Model B", rpi_b_plus_init),
         RPI_MODEL(BCM2837_BOARD_REV_3_B, "3 Model B", rpi_b_plus_init),
+       RPI_MODEL(10, "Compute Module 3", NULL),
         RPI_MODEL(BCM2835_BOARD_REV_ZERO, "Zero", rpi_b_plus_init),
         RPI_MODEL(BCM2835_BOARD_REV_ZERO_W, "Zero W", rpi_b_plus_init),
  };
@@ -251,6 +252,9 @@

  static void rpi_model_init(void)
  {
+       if (!model)
+               return;
+
         if (!model->init)
                 return;
diff -ru a/arch/arm/dts/bcm2837-rpi-3.dts b/arch/arm/dts/bcm2837-rpi-3.dts
--- a/arch/arm/dts/bcm2837-rpi-3.dts    2019-01-14 09:05:44.000000000 +0100
+++ b/arch/arm/dts/bcm2837-rpi-3.dts    2019-02-11 09:49:55.000000000 +0100
@@ -1,4 +1,5 @@
-#include <arm64/broadcom/bcm2837-rpi-3-b.dts>
+//#include <arm64/broadcom/bcm2837-rpi-3-b.dts>
+#include <arm/bcm2837-rpi-cm3-io3.dts>

  / {
         chosen {

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