[PATCH v1 3/4] arm64: Add arm64 kexec support

On Fri, Jul 22, 2016 at 09:38:42AM +0530, Pratyush Anand wrote:

On 21/07/2016:02:49:36 PM, Geoff Levand wrote:

quoted

On Thu, 2016-07-21 at 11:50 +0100, Robin Murphy wrote:

quoted

The Exynos UART (drivers/tty/serial/samsung.c) is one which comes to
mind as definitely existing, and on arm64 systems to boot. The TX
register is at offset 0x20 there.

Here's what I came up with.


+	struct data {const char *name; int tx_offset;};
+	static const struct data ok_list[] = {
+	/*	{"armada-3700-uart", ?},	*/
+		{"exynos4210-uart", 0x20},
+	/*	{"ls1021a-lpuart", ?},		*/
+	/*	{"meson-uart", ?},		*/
+	/*	{"mt6577-uart", ?},		*/
+		{"ns16550", 0},
+		{"ns16550a", 0},
+		{"pl011", 0},
+		{NULL, 0}
+	};

sinc functionality is just to debug the scenario when something goes wrong in
purgatory. IMHO, it should be disabled by default.

+1

-Takahiro AKASHI

So, why not to keep it as
simple as possible. Its a low level debugging mainly for developer, so user
should know the absolute address. Therefore, I think no need to parse earlycon
or earlyprintk from command line.  Whatever user passes in --port can be treated
as address of TX register. If TX offset is 0x20, then user can pass --port as
base+0x20. Additionally, we can pass TX register width as well. So what about
something like "--port=0x1c020000,1" where 0x1c020000 is TX register address and
1 says about it's width in bytes.

~Pratyush