lkml.org 
[lkml]   [2018]   [May]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/4] amba: Export amba_bustype
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 <mathieu.poirier@linaro.org>
> >Cc: Alex Williamson <alex.williamson@redhat.com>
> >Cc: Eric Auger <eric.auger@redhat.com>
> >Cc: Russell King <linux@armlinux.org.uk>
> >Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> >Cc: Todd Kjos <tkjos@google.com>
> >Cc: Geert Uytterhoeven <geert+renesas@glider.be>
> >Cc: Thierry Reding <treding@nvidia.com>
> >Cc: Robin Murphy <robin.murphy@arm.com>
> >Signed-off-by: Kim Phillips <kim.phillips@arm.com>
> >---
> >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 <robin.murphy@arm.com>
>
> 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.

Mathieu

>

\
 
 \ /
  Last update: 2018-05-09 17:41    [W:0.140 / U:0.072 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site