Hi,
On Friday 31 August 2012 01:58 PM, Archit Taneja wrote:
On Friday 31 August 2012 01:57 PM, Tomi Valkeinen wrote:
On Fri, 2012-08-31 at 13:50 +0530, Archit Taneja wrote:
On Friday 31 August 2012 12:45 PM, Tomi Valkeinen wrote:
On Fri, 2012-08-31 at 11:53 +0530, Archit Taneja wrote:
The only little problem was that during bootup, when hwmods are setup,
only the 'parent' hwmod was able to get reset properly, all the other
'child' hwmods don't have modulemode bits tied to them, and hence
weren't able to reset. So we got some error prints.
Once DSS driver kicks in, the driver ensures the parent is enabled for
any child to be enabled, so we don't face the issue again.
So, if DSS driver is not built in, and if the bootloader left DSS in a
bad state, the DSS clocks might remain messed up all the time since
hwmod fwk wasn't able to reset them.
I think this is why we didn't proceed with remove "dss_fck" as a slave
clock. If this issue is minor, we could go ahead and remove it.
I wonder if we could handle this with a custom reset function. We
already have a reset func for dss core. If I remember right, the main
point for that is the fact that omap4 doesn't have a softreset for dss
core, so we manually write the default values to registers.
For omap2/3 this would be simple: skip the resets for all other dss
submodules, and dss core's reset would enable all the clocks and set
the
softreset bit. This would reset all the submodules also.
Omap4 is more tricky. I guess we'd need to enable all the clocks, clear
manually dss core's registers, and then set softreset bits in all the
submodules. So in this case dss core would need to have information
about the other submodules.
The is a good idea. I don't clearly understand your approach though. Are
you saying we have a custom reset function for only dss core? And reset
the submodules in it manually?
Yes.
An alternative approach would be to implement custom reset functions for
each submodule(or each hwmod), and in the beginning of every reset
function, add a hack to enable MODULEMODE bits(since we don't want hwmod
fwk to touch MODULEMODE for the DSS submodules), and then set the soft
reset bits.
I thought about that also. We'd need reset functions for all of them,
and for omap2/3 we'd just reset the submodules again as they have
already been reset with the dss core reset.
The dss submodule resets are a bit linked. For omap2/3 the connection is
obvious as dss core reset resets also the submodules, and for omap4 we
have this requirement for the modulemode. That's why I though it'd be
perhaps cleaner to handle the reset of the DSS block as a whole, in one
place.
Your approach would ensure that we get a clean reset of DSS, but it
would still give the annoying prints when each of the submodule tries to
reset itself.
The other submodules would not be reset by the hwmod framework at all,
so there wouldn't be prints. I think there's a flag for that.
Sorry for bringing up an old thread. I was working on cleaning up the
OMAP4 DSS related clock/pm issues, hence brought it up.
We were discussing here on how to setting up and reset the OMAP4 DSS
submodules correctly without tying the MODULEMODE bits to the
corresponding hwmods.
Tomi, your suggestion was to do soft resets for the submodules manually
in the dss_core hwmod's custom reset function itself, and use the flag
HWMOD_INIT_NO_RESET to prevent _reset() being called.
However, this won't still resolve the issue of the errors we see a
bootup. The function _setup_reset() looks like this:
static int _setup_reset(struct omap_hwmod *oh)
{
...
r = _enable(oh);
if (r) {
pr_warning("omap_hwmod: %s: cannot be enabled for
reset (%d)\n", oh->name, oh->_state);
return -EINVAL;
}
...
if (!(oh->flags & HWMOD_INIT_NO_RESET))
r = _reset(oh);
...
}
So, even if we have ask hwmod not to reset the DSS submodules, it will
still try to enable them, and we can't enable them since MODULEMODE
isn't tied to them. I don't see how we can get a clean reset done for
the DSS submodules without making some changes in hwmod framework.
Archit
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