[PATCH 4/8] tty/serial: add generic serial earlycon

On Mon, Mar 24, 2014 at 6:29 AM, Arnd Bergmann [off-list ref] wrote:

On Monday 24 March 2014 11:22:03 Catalin Marinas wrote:

quoted

On Fri, Mar 21, 2014 at 09:08:44PM +0000, Rob Herring wrote:

quoted

diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c
new file mode 100644
index 0000000..241757a
--- /dev/null
+++ b/drivers/tty/serial/earlycon.c

[...]

quoted

+static void __iomem * __init earlycon_map(unsigned long paddr, size_t size)
+{
+   void __iomem *base;
+#ifdef CONFIG_FIX_EARLYCON_MEM
+   set_fixmap_nocache(FIX_EARLYCON_MEM_BASE, paddr & PAGE_MASK);
+   base = (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE);
+   base += paddr & ~PAGE_MASK;
+#else
+   base = ioremap_nocache(paddr, size);
+#endif

Just curious why not set_fixmap_io (and plain ioremap)?

Good point. Note that ioremap_nocache() is the same as ioremap()
on *all* architectures.

I investigated this before adding this to arm64. set_fixmap_io and
set_fixmap_nocache are not the same settings on x86. Whether the
mapping type really matters on x86 or not, I don't know. So I added
the nocache variant to arm64 to avoid a change to x86.

Rob