On 2014-12-03 12:03, Arnd Bergmann wrote:

On Wednesday 03 December 2014 01:12:10 Stefan Agner wrote:

quoted

diff --git a/arch/arm/boot/dts/vf610m4-colibri.dts b/arch/arm/boot/dts/vf610m4-colibri.dts
new file mode 100644
index 0000000..051ee0f
--- /dev/null
+++ b/arch/arm/boot/dts/vf610m4-colibri.dts

@@ -0,0 +1,52 @@
+/*
+ * Device tree for Colibri VF61 Cortex-M4 support
+ *
+ * Copyright 2014 Stefan Agner
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+/dts-v1/;
+#include "vf610m4.dtsi"
+
+/ {
+       model = "VF610 Cortex-M4";
+       compatible = "fsl,vf610m4";
+
+       chosen {
+               bootargs = "console=ttyLP2,115200 ihash_entries=64 dhash_entries=64 earlyprintk clk_ignore_unused init=/linuxrc rw";
+       };
+

Starting with v3.19, you should be able to use the earlycon framework on
arm32, so it would be better to replace earlyprintk with earlycon here
and add a stdout-path property in chosen that points to the console
uart.

I started to implement earlycon support, but something currently fails
when earlycon tries to map the UART registers:
[    0.000000] earlycon_map: Couldn't map 0x40027000

I traced the issue a bit further down and found that get_vm_area_caller
returns NULL (in __arm_ioremap_pfn_caller). This happend on Linus master
as of today (2dbfca5a181973558277b28b1f4c36362291f5e0). Do I miss
something here?

64 hash table entries sounds extremely small, doesn't that impact
performance? If you have 50MB of actual RAM available, I don't think
you need that.

	Arnd