From: John Rigby <hidden> Date: 2007-03-29 21:20:21
I have a question about the "right" way to publish platform
devices via of_platform_bus_probe.
On 5200 platforms it gets called from
mpc52xx_declare_of_platform_devices which is registered as the
machdep_calls init routine.
On other platforms it is called via a device_initcall
I assume the main difference between these two is one would happen
later than the other?
Also I noticed that some 83xx platforms don't call
of_platform_bus_probe at all. Thats ok because most of those devices
are register various routines in fsl_soc.c. The one I have not
figured out yet is spi, I don't see anyone registering mpc83xx_spi?
Any enlightenment would be appreciated
Thanks
John
I have a question about the "right" way to publish platform
devices via of_platform_bus_probe.
On 5200 platforms it gets called from
mpc52xx_declare_of_platform_devices which is registered as the
machdep_calls init routine.
It's called by machdep calls so that it's only called if the platform is
detected ...
On other platforms it is called via a device_initcall
That will always be called which is bad.
Because if you have a kernel will multiple platform support built in, it
will
be called everytime, even if it's not running on the good platform.
Also I noticed that some 83xx platforms don't call
of_platform_bus_probe at all. Thats ok because most of those devices
are register various routines in fsl_soc.c. The one I have not
figured out yet is spi, I don't see anyone registering mpc83xx_spi?
From: Kim Phillips <hidden> Date: 2007-03-29 21:56:23
On Thu, 29 Mar 2007 23:26:39 +0200
Sylvain Munaut [off-list ref] wrote:
John Rigby wrote:
quoted
I have a question about the "right" way to publish platform
devices via of_platform_bus_probe.
On 5200 platforms it gets called from
mpc52xx_declare_of_platform_devices which is registered as the
machdep_calls init routine.
It's called by machdep calls so that it's only called if the platform
is detected ...
quoted
On other platforms it is called via a device_initcall
That will always be called which is bad.
Because if you have a kernel will multiple platform support built in,
it will
be called everytime, even if it's not running on the good platform.
quoted
Also I noticed that some 83xx platforms don't call
of_platform_bus_probe at all. Thats ok because most of those
devices are register various routines in fsl_soc.c. The one I have
not figured out yet is spi, I don't see anyone registering
mpc83xx_spi?
On theses I have no idea ...
spi_mpc83xx is a platform_driver. You either have to add spi code to
fsl_soc.c, or, probably better, make it an of_platform_driver (see
drivers/net/ucc_geth.c). Hopefully an of_platform_driver patch will
be accepted now that cuimage is here, and 83xx can be removed from arch/ppc.
Kim
I have a question about the "right" way to publish platform
devices via of_platform_bus_probe.
On 5200 platforms it gets called from
mpc52xx_declare_of_platform_devices which is registered as the
machdep_calls init routine.
=A0=20
It's called by machdep calls so that it's only called if the platform is
detected ...
quoted
On other platforms it is called via a device_initcall
=A0=20
That will always be called which is bad.
=20
Because if you have a kernel will multiple platform support built in, it
will
be called everytime, even if it's not running on the good platform.
The ppc_md->init() function is currently only present on 32 bit,
if we decide that this is the way to go, we should make it common
to both 32 and 64 bit platforms.
quoted
Also I noticed that some 83xx platforms don't call
of_platform_bus_probe at all. =A0Thats ok because most of those devices
are register various routines in fsl_soc.c. =A0The one I have not
figured out yet is spi, I don't see anyone registering mpc83xx_spi?
On theses I have no idea ...
They should be converted to use of_platform_bus_probe in the future. As soon
as we have of_platform_drivers for the devices probed in fsl_soc.c, we can
get rid of that file.
Arnd <><
From: Benjamin Herrenschmidt <benh@kernel.crashing.org> Date: 2007-03-29 22:07:41
The ppc_md->init() function is currently only present on 32 bit,
if we decide that this is the way to go, we should make it common
to both 32 and 64 bit platforms.
I still think we should do something like platform_xxx_initcall(); with
xxx being {core,subsys,device,...} ... I'll look into it. ppc_md.init()
is a bit gross.
Ben.
On Friday 30 March 2007, Benjamin Herrenschmidt wrote:
quoted
The ppc_md->init() function is currently only present on 32 bit,
if we decide that this is the way to go, we should make it common
to both 32 and 64 bit platforms.
I still think we should do something like platform_xxx_initcall(); with
xxx being {core,subsys,device,...} ... I'll look into it. ppc_md.init()
is a bit gross.
Yes, that sounds like a good idea, but I'd much prefer adding these only
if they actually simplify the existing code, rather than having them
for completeness.
We also might want to have something a lot simpler at first. Since
many platforms just want to call
of_platform_bus_probe(NULL, foo_ids, NULL);
There could simply be an entry in ppc_md that gets set to foo_ids
and we call of_platform_bus_probe() with that, and get rid of the
unused root and parent arguments.
Arnd <><
From: Benjamin Herrenschmidt <benh@kernel.crashing.org> Date: 2007-03-29 22:25:49
On Fri, 2007-03-30 at 00:18 +0200, Arnd Bergmann wrote:
On Friday 30 March 2007, Benjamin Herrenschmidt wrote:
quoted
quoted
The ppc_md->init() function is currently only present on 32 bit,
if we decide that this is the way to go, we should make it common
to both 32 and 64 bit platforms.
I still think we should do something like platform_xxx_initcall(); with
xxx being {core,subsys,device,...} ... I'll look into it. ppc_md.init()
is a bit gross.
Yes, that sounds like a good idea, but I'd much prefer adding these only
if they actually simplify the existing code, rather than having them
for completeness.
They will at first generate something like:
static int func(void)
{
if (!machine_is(platform))
return 0;
return user_func();
}
xxx_initcall(func);
And thus will be equivalent in generated code to the open coded
versions, but that is already enough to avoid, I hope, quite a bit of
mistakes and simplify the source.
Later on, we can look into doing some smart ELF section tricks to also
reduce the generated code.
We also might want to have something a lot simpler at first. Since
many platforms just want to call
of_platform_bus_probe(NULL, foo_ids, NULL);
There could simply be an entry in ppc_md that gets set to foo_ids
and we call of_platform_bus_probe() with that, and get rid of the
unused root and parent arguments.
Might not be unused forever... oh well, we'll see.
Ben.