On Mon, 28 Apr 2014 13:02:28 -0500, Rob Herring [off-list ref] wrote:

On Mon, Apr 28, 2014 at 12:57 PM, Pawel Moll [off-list ref] wrote:

quoted

In "Device Tree powered" systems, platform devices are usually
massively populated with of_platform_populate() call, executed
at some level of initcalls, either by generic architecture
or by platform-specific code.

There are situations though where certain devices must be
created (and bound with drivers) before all the others.
This presents a challenge, as devices created explicitly
would be created again by of_platform_populate().

This patch tries to solve that issue in a generic way,
adding a "populated" flag for a DT node description.
Once set, this device will never be created again via
of_* API, so of_platform_populate() will skip such nodes
(and its children) in a similar way to the non-available
ones.

Cc: devicetree at vger.kernel.org
Signed-off-by: Pawel Moll <redacted>
---
 drivers/of/platform.c | 10 ++++++++--
 include/linux/of.h    |  1 +
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index 404d1da..0ae757a 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c

@@ -204,7 +204,8 @@ static struct platform_device *of_platform_device_create_pdata(
 {
        struct platform_device *dev;

-       if (!of_device_is_available(np))
+       if (!of_device_is_available(np) ||
+                       of_node_check_flag(np, OF_POPULATED))

This and the amba case should be a test_and_set operation to avoid a
race condition.

Yes. It is an unlikely condition at the time that Pawel is handling, but
it should also work for later calls to of_platform_populate() which may
happen at runtime and in parallel.

g.