dt-uart: support /chosen/stdout-path property.

ePAPR v1.1 section 3.5 defines the /chosen/stdout-path property to
refer to the device to be used for boot console output, so if no
dtuart property is given try to use that instead. This will make Xen
find a suitable console by default on DT platforms which include this
property.

As it happens the dtuart option has the exact same syntax as
stdout-path, so we can just copy the value into that buffer if it is
empty. If the string is too large for the buffer we truncate and warn
but continue in the hopes that enough of the path survived (i.e. only
the options part was dropped) to get something out.

FWIW support for this was added to Linux in v3.19-rc1 (7914a7c5651a
"of: support passing console options with stdout-path") and a fairly
large number of the dts files shipped with Linux have already included
a stdout-path property for quite a while now.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: Julien Grall <julien.grall@linaro.org>

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index de180d88fb9863fb56608edf477778ed594d8796..c33a73c63eceeec4980d4cbf19e571e2ed178e9e 100644 (file)
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -424,6 +424,7 @@ static int write_properties(struct domain *d, struct kernel_info *kinfo,
          *   bootargs (from module #1, above).
          * * remove bootargs,  xen,dom0-bootargs, xen,xen-bootargs,
          *   linux,initrd-start and linux,initrd-end.
+         * * remove stdout-path.
          * * remove bootargs, linux,uefi-system-table,
          *   linux,uefi-mmap-start, linux,uefi-mmap-size,
          *   linux,uefi-mmap-desc-size, and linux,uefi-mmap-desc-ver
@@ -434,6 +435,7 @@ static int write_properties(struct domain *d, struct kernel_info *kinfo,
             if ( dt_property_name_is_equal(prop, "xen,xen-bootargs") ||
                  dt_property_name_is_equal(prop, "linux,initrd-start") ||
                  dt_property_name_is_equal(prop, "linux,initrd-end") ||
+                 dt_property_name_is_equal(prop, "stdout-path") ||
                  dt_property_name_is_equal(prop, "linux,uefi-system-table") ||
                  dt_property_name_is_equal(prop, "linux,uefi-mmap-start") ||
                  dt_property_name_is_equal(prop, "linux,uefi-mmap-size") ||

diff --git a/xen/drivers/char/dt-uart.c b/xen/drivers/char/dt-uart.c
index 695fdaab363e7e8e332b3cca2c23d76cd39b3dbd..d599322a2472708caf33ed93fab571d65268bd61 100644 (file)
--- a/xen/drivers/char/dt-uart.c
+++ b/xen/drivers/char/dt-uart.c
@@ -22,6 +22,7 @@
 #include <xen/console.h>
 #include <xen/device_tree.h>
 #include <xen/serial.h>
+#include <xen/errno.h>
 
 /*
  * Configure UART port with a string:
@@ -44,6 +45,27 @@ void __init dt_uart_init(void)
     if ( !console_has("dtuart") )
         return; /* Not for us */
 
+    if ( !strcmp(opt_dtuart, "") )
+    {
+        const struct dt_device_node *chosen = dt_find_node_by_path("/chosen");
+
+        if ( chosen )
+        {
+            const char *stdout;
+
+            ret = dt_property_read_string(chosen, "stdout-path", &stdout);
+            if ( ret >= 0 )
+            {
+                printk("Taking dtuart configuration from /chosen/stdout-path\n");
+                if ( strlcpy(opt_dtuart, stdout, sizeof(opt_dtuart))
+                     >= sizeof(opt_dtuart) )
+                    printk("WARNING: /chosen/stdout-path too long, truncated\n");
+            }
+            else if ( ret != -EINVAL /* Not present */ )
+                printk("Failed to read /chosen/stdout-path (%d)\n", ret);
+        }
+    }
+
     if ( !strcmp(opt_dtuart, "") )
     {
         printk("No dtuart path configured\n");