On 09/05/18 16:40, Mathieu Poirier wrote:
On Wed, May 09, 2018 at 02:38:32PM +0100, Robin Murphy wrote:
Hi Kim,
On 08/05/18 20:06, Kim Phillips wrote:
This patch is provided in the context of allowing the Coresight driver
subsystem to be loaded as modules. Coresight uses amba_bus in its call
to bus_find_device() in of_coresight_get_endpoint_device() when
searching for a configurable endpoint device. This patch allows
Coresight to reference amba_bustype when built as a module.
Cc: Mathieu Poirier <[email protected]>
Cc: Alex Williamson <[email protected]>
Cc: Eric Auger <[email protected]>
Cc: Russell King <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Todd Kjos <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Thierry Reding <[email protected]>
Cc: Robin Murphy <[email protected]>
Signed-off-by: Kim Phillips <[email protected]>
---
There was a prior patch submitted by Alex W. here:
https://lkml.org/lkml/2017/6/19/811
But I can't tell its fate - presume simply delayed?
Coresight uses amba_bus in its call to bus_find_device() here:
https://lxr.missinglinkelectronics.com/linux/drivers/hwtracing/coresight/of_coresight.c#L51
Grepping for bus_type and EXPORT shows other busses exporting their
type, so I don't think this is the wrong approach. If, OTOH, Coresight
needs to do something differently, please comment.
Exposing raw bus_types is pretty ugly, but it is indeed the status quo, so
this probably is the reasonable thing to do. I suppose an amba_bus
equivalent of of_find_device_by_node() could be implemented, but for only a
single potential user that doesn't seem particularly worthwhile, since
unless some massive shake-up of how buses work comes along the bus_type will
inevitably end up being exported for other reasons anyway. So, in the
context of this series;
Reviewed-by: Robin Murphy <[email protected]>
However, as a wild idea for sidestepping the issue completely (or at least
keeping it within the CoreSight framework), at first glance it appears
something like the below might be feasible, although I may well be missing
some obvious reason why not.
Thanks,
Robin.
----->8-----
diff --git a/drivers/hwtracing/coresight/of_coresight.c
b/drivers/hwtracing/coresight/of_coresight.c
index 7c375443ede6..2c3fdc9b63e6 100644
--- a/drivers/hwtracing/coresight/of_coresight.c
+++ b/drivers/hwtracing/coresight/of_coresight.c
@@ -27,28 +27,13 @@
static int of_dev_node_match(struct device *dev, void *data)
{
- return dev->of_node == data;
+ return dev->parent->of_node == data;
}
static struct device *
of_coresight_get_endpoint_device(struct device_node *endpoint)
{
- struct device *dev = NULL;
-
- /*
- * If we have a non-configurable replicator, it will be found on the
- * platform bus.
- */
- dev = bus_find_device(&platform_bus_type, NULL,
- endpoint, of_dev_node_match);
- if (dev)
- return dev;
-
- /*
- * We have a configurable component - circle through the AMBA bus
- * looking for the device that matches the endpoint node.
- */
- return bus_find_device(&amba_bustype, NULL,
+ return bus_find_device(&coresight_bustype, NULL,
endpoint, of_dev_node_match);
}
Hi Robin and thanks for the input.
Your approach would work if all CS devices would be on the CS bus, which is not
the case at discovery time when of_coresight_get_endpoint_device() is called.
Ah, now I see that obvious thing I was indeed missing - I got mixed up
and started thinking bus_add_device() only got called as part of driver
probe, but of course it's actually much earlier in
{platform,amba}_device_add(). That means my idea cannot in fact work at
all, since both ends of any link would defer waiting for the other to
probe (and thus call coresight_register()) first. Oh well, I guess
poking amba_bustype really does remain the only reasonable answer.
Thanks,
Robin.
