Re: [RFC PATCH] dt: describe base reset signal binding

Quoting Stephen Warren (2012-10-30 11:02:05)

On 10/29/2012 12:32 PM, Mike Turquette wrote:

quoted

Quoting Stephen Warren (2012-10-23 14:45:56)

quoted

What do people think of this? Does it sound like a good idea to go ahead
with a reset subsystem? Should we simply add a new API to the common clock
subsystem instead (and assume that reset and clock domains match 1:1).
Should this be implemented as part of the generic power management domains;
see include/linux/pm_domain.h instead?

Hi Stephen,

I'm not sure a "reset subsystem" is necessary, but I also do not like
using clocks as the keys for IP reset.

I'm not sure what you're suggesting as an alternative to a reset
subsystem (or API if you want something that sounds smaller!) :-)

My point was that I do not know if a new subsystem is necessary or not.
Your suggestion to "simply add a new API to the common clock subsystem"
is an example of an alternative to a whole new subsystem.  However I
instinctively feel that the clock api is not the right place for
reseting devices.

quoted

I think it is more common to map IPs to struct device, no?

It is indeed probably common that there's a 1:1 mapping between IP
blocks and struct device. However, I'm sure there are plenty of
counter-examples; IP blocks with multiple reset domains (hence struct
devices that encompass multiple reset domains, or reset domains that
encompass multiple struct devices), just as there are many examples of
non-1:1 mappings between struct device and struct clk.

In OMAP code we handle IP resets through the hwmod code and I prefer
that IP-centric approach to associating IP resets with a clock node.
Perhaps the hwmod approach could serve as inspiration for a new generic
way to reset modules.

Even ignoring that, we'd still need to API say device_reset(struct
device *dev) or device_reset(struct device *dev, const char *conid)
wouldn't we? That's really all I meant by a reset subsystem.

Of course.  The api must exist.

An alternative here would be to simply move Tegra's
tegra_periph_reset_{de,}assert() function prototypes into a header in
include/linux rather than mach-tegra/include/mach. However, I imagine at
least some other SoC needs a similar API, so a common API might be useful?

I also agree.  I think that there was simply some confusion about how I
responded.  To reiterate, I'm not sure whether a new subsystem should be
created or if the API can find a home in some existing subsystem, but I
don't think the clock framework is the right place for it.

Regards,
Mike