ARM: bcm2835: expand Kconfig target descriptions

This adds an explanation of which Raspberry Pi models each target option
supports.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Reviewed-by: Tom Rini <trini@konsulko.com>

diff --git a/arch/arm/mach-bcm283x/Kconfig b/arch/arm/mach-bcm283x/Kconfig
index dc67704..1f3031d 100644 (file)
--- a/arch/arm/mach-bcm283x/Kconfig
+++ b/arch/arm/mach-bcm283x/Kconfig
@@ -14,12 +14,38 @@ choice
        optional
 
 config TARGET_RPI
-       bool "Raspberry Pi"
+       bool "Raspberry Pi (all BCM2835 variants)"
+       help
+         Support for all ARM1176-/BCM2835-based Raspberry Pi variants, such as
+         the A, A+, B, B+, Compute Module, and Zero. This option cannot
+         support BCM2836/BCM2837-based Raspberry Pis such as the RPi 2 and
+         RPi 3 due to different peripheral address maps.
+
+         This option creates a build targetting the ARM1176 ISA.
        select BCM2835
        select CPU_ARM1176
 
 config TARGET_RPI_2
        bool "Raspberry Pi 2"
+       help
+         Support for all BCM2836-based Raspberry Pi variants, such as
+         the RPi 2 model B.
+
+         This option also supports BCM2837-based variants such as the RPi 3
+         Model B, when run in 32-bit mode, provided you have configured the
+         VideoCore firmware to select the PL011 UART for the console by:
+         a) config.txt should contain dtoverlay=pi3-miniuart-bt.
+         b) You should run the following to tell the VC FW to process DT when
+         booting, and copy u-boot.bin.img (rather than u-boot.bin) to the SD
+         card as the kernel image:
+
+              path/to/kernel/scripts/mkknlimg --dtok u-boot.bin u-boot.bin.img
+
+         This works as of firmware.git commit 046effa13ebc "firmware:
+         arm_loader: emmc clock depends on core clock See:
+         https://github.com/raspberrypi/firmware/issues/572".
+
+         This option creates a build targetting the ARMv7/AArch32 ISA.
        select ARMV7_LPAE
        select BCM2836
        select CPU_V7