Cleaned up patch which underclocks the SDIO bus on E200 boards,
derived from UBNT GPL sources (ubnt_prune_device_tree).

Signed-off-by: Ariadne Conill <ariadne@dereferenced.org>
--- linux-5.4.orig/arch/mips/cavium-octeon/octeon-platform.c
+++ linux-5.4/arch/mips/cavium-octeon/octeon-platform.c
@@ -1128,6 +1128,20 @@
 	}
 #endif
 
+	/* UBNT underclocks the SDIO bus on E200.  We do the same here. */
+	if (octeon_bootinfo->board_type == CVMX_BOARD_TYPE_UBNT_E200 || octeon_bootinfo->board_type == CVMX_BOARD_TYPE_UBNT_E220) {
+		int mmc_slot0;
+		u32 freq = 26000000;
+
+		pr_info("UBNT E200 board detected, underclocking SDIO bus.\n");
+
+		mmc_slot0 = fdt_path_offset(initial_boot_params, "/soc/mmc/mmc-slot@0");
+		if (mmc_slot0 > 0) {
+			fdt_setprop_inplace_cell(initial_boot_params, mmc_slot0,
+				"spi-max-frequency", freq);
+		}
+	}
+
 	return 0;
 }
 
--- linux-5.4.orig/arch/mips/include/asm/octeon/cvmx-bootinfo.h
+++ linux-5.4/arch/mips/include/asm/octeon/cvmx-bootinfo.h
@@ -295,6 +295,9 @@
 	 */
 	CVMX_BOARD_TYPE_CUST_PRIVATE_MIN = 20001,
 	CVMX_BOARD_TYPE_UBNT_E100 = 20002,
+	CVMX_BOARD_TYPE_UBNT_E200 = 20003,
+	CVMX_BOARD_TYPE_UBNT_E120 = 20004,
+	CVMX_BOARD_TYPE_UBNT_E220 = 20005,
 	CVMX_BOARD_TYPE_CUST_DSR1000N = 20006,
 	CVMX_BOARD_TYPE_KONTRON_S1901 = 21901,
 	CVMX_BOARD_TYPE_CUST_PRIVATE_MAX = 30000,
@@ -396,6 +399,9 @@
 		    /* Customer private range */
 		ENUM_BRD_TYPE_CASE(CVMX_BOARD_TYPE_CUST_PRIVATE_MIN)
 		ENUM_BRD_TYPE_CASE(CVMX_BOARD_TYPE_UBNT_E100)
+		ENUM_BRD_TYPE_CASE(CVMX_BOARD_TYPE_UBNT_E200)
+		ENUM_BRD_TYPE_CASE(CVMX_BOARD_TYPE_UBNT_E120)
+		ENUM_BRD_TYPE_CASE(CVMX_BOARD_TYPE_UBNT_E220)
 		ENUM_BRD_TYPE_CASE(CVMX_BOARD_TYPE_CUST_DSR1000N)
 		ENUM_BRD_TYPE_CASE(CVMX_BOARD_TYPE_KONTRON_S1901)
 		ENUM_BRD_TYPE_CASE(CVMX_BOARD_TYPE_CUST_PRIVATE_MAX)