We need this to boot with a custom DTB on BCM2711C0-based Pi 4s
Signed-off-by: Ilya Katsnelson <m...@0upti.me>
---
board/raspberrypi/rpi/rpi.c | 63 +++++++++++++++++++++++++++++++++++++
1 file changed, 63 insertions(+)
diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c
index 372b26b6f2..f074540091 100644
--- a/board/raspberrypi/rpi/rpi.c
+++ b/board/raspberrypi/rpi/rpi.c
@@ -495,6 +495,67 @@ void *board_fdt_blob_setup(void)
return (void *)fw_dtb_pointer;
}
+void copy_emmc_config(void *our_fdt)
+{
+ /*
+ * As of 2021-09-28, the Pi 4 has two different revisions, one using a
+ * B0 stepping of the BCM2711 SoC, and one using a C0 stepping.
+ *
+ * The two SoC versions have different, incompatible DMA mappings for
+ * the on-board eMMC controller, which would normally make them require
+ * two different DTs.
+ *
+ * Unfortunately for us, the different revisions don't actually _use_
+ * different DTs - instead, the proprietary stage0 bootloader reads the
DT,
+ * patches it in-memory, then passes the corrected DT to the OS.
+ *
+ * In our case, the OS is actually U-Boot, and U-Boot can choose to
+ * completely disregard the firmware-supplied DT and load a custom one
+ * instead, which is used by, e.g., NixOS.
+ *
+ * When that happens, the DT patches applied by the firmware are also
+ * thrown out, which leads to BCM2711C0 boards being unable to boot
+ * due to them trying to use the hardcoded DMA mappings in the DT
+ * (which are for the B0 revision).
+ *
+ * Work around that by manually copying the DMA region setup from the
+ * firmware-provided DT into whatever DT we're actually being asked
+ * to load.
+ A*/
+ void *fw_fdt = (void *)fw_dtb_pointer;
+ int fw_emmc_node;
+ int our_emmc_node;
+ int length;
+ const void *fw_value;
+ int result;
+
+ fw_emmc_node = fdt_path_offset(fw_fdt, "emmc2bus");
+ if (fw_emmc_node < 0) {
+ printf("RPi: Failed to find EMMC config in FW DT: %d\n",
fw_emmc_node);
+ return;
+ }
+
+ our_emmc_node = fdt_path_offset(our_fdt, "emmc2bus");
+ if (our_emmc_node < 0) {
+ printf("RPi: Failed to find EMMC config in our DT: %d\n",
our_emmc_node);
+ return;
+ }
+
+ *fw_value = fdt_getprop(fw_fdt, fw_emmc_node, "dma-ranges", &length);
+ if (!fw_value) {
+ printf("RPi: Failed to get EMMC DMA ranges property from FW DT:
%d\n", length);
+ return;
+ }
+
+ result = fdt_setprop(our_fdt, our_emmc_node, "dma-ranges", fw_value,
length);
+ if (result != 0) {
+ printf("RPi: Failed to set EMMC DMA ranges property in our DT:
%d\n", result);
+ return;
+ }
+
+ printf("RPi: successfully copied FW DT EMMC configuration to our
DT!\n");
+}
+
int ft_board_setup(void *blob, struct bd_info *bd)
{
int node;
@@ -509,5 +570,7 @@ int ft_board_setup(void *blob, struct bd_info *bd)
EFI_RESERVED_MEMORY_TYPE);
#endif
+ copy_emmc_config(blob);
+
return 0;
}
--
2.33.0
