memory: mvebu-devbus: add a devbus, keep-config property

Currently, the mvebu-devbus Device Tree binding makes defining the
timing parameters mandatory.

However, in practice, when converting Orion5x platforms to the Device
Tree, we may not necessarily have easy access to the hardware
platforms to fetch those values which were not defined in old-style
board files: all these platforms rely on the bootloader setting the
timing parameters correctly.

In order to facilitate the migration to the Device Tree of this
platform, this commit relaxes the mvebu-devbus Device Tree binding by
introducing a 'devbus,keep-config' boolean property, which, if
defined, will ignore all timing parameters passed in the Device Tree,
and simply rely on the timing values already defined by the
bootloader.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Tested-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Link: https://lkml.kernel.org/r/1398202002-28530-10-git-send-email-thomas.petazzoni@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

1 files changed, 11 insertions, 9 deletions

diff --git a/drivers/memory/mvebu-devbus.c b/drivers/memory/mvebu-devbus.c
index c8f3dad8a825..ff7138fd66d1 100644
--- a/drivers/memory/mvebu-devbus.c
+++ b/drivers/memory/mvebu-devbus.c
@@ -310,16 +310,18 @@ static int mvebu_devbus_probe(struct platform_device *pdev)
         dev_dbg(devbus->dev, "Setting timing parameter, tick is %lu ps\n",
                 devbus->tick_ps);
 
-        /* Read the Device Tree node */
-        err = devbus_get_timing_params(devbus, node, &r, &w);
-        if (err < 0)
-                return err;
+        if (!of_property_read_bool(node, "devbus,keep-config")) {
+                /* Read the Device Tree node */
+                err = devbus_get_timing_params(devbus, node, &r, &w);
+                if (err < 0)
+                        return err;
 
-        /* Set the new timing parameters */
-        if (of_device_is_compatible(node, "marvell,orion-devbus"))
-                devbus_orion_set_timing_params(devbus, node, &r, &w);
-        else
-                devbus_armada_set_timing_params(devbus, node, &r, &w);
+                /* Set the new timing parameters */
+                if (of_device_is_compatible(node, "marvell,orion-devbus"))
+                        devbus_orion_set_timing_params(devbus, node, &r, &w);
+                else
+                        devbus_armada_set_timing_params(devbus, node, &r, &w);
+        }
 
         /*
          * We need to create a child device explicitly from here to