On 20/01/2017 06:56, Peter Rosin wrote:
On 2017-01-19 08:48, Phil Reid wrote:
On 18/01/2017 20:19, Peter Rosin wrote:
On 2017-01-17 09:00, Phil Reid wrote:
[snip]
Hmm, this whole thing is fiddly and while it solves your problem it doesn't
allow for solving the more general problem when there are "problematic"
devices mixed with other devices. At least, I don't see it. And the
limitations we are walking into with tracking number of enables etc suggests
that we are attacking this at the wrong level. Maybe you should try to work
around the hw limitations not in the pca954x driver, but in the irq core?
I'm looking at the option of getting the hardware changed to not route
the irq for my chips thru the i2c mux. Fortunately the hardware is going thru a
revision for some other changes. Messing with the irq core sounds dangerous
with my level of knowledge.
Yeah, but I bet you'd get some attention from people with more irq
experience. That can't be bad :-)
The other way I think I can tackle it after reading the datasheet for the ltc1760 is that
it'll deassert it's irq (smbalert) line when the host sends a ARA request on the bus segment.
There's a driver in the kernel for this already, but it's not DT enable and doesn't
handle multiple bus segments. I'll have a look at that as well.
Pretty sure it would need the mux to become an irq parent as per patch 1-3 of this series.
This would be so the system can figure out which segment to do the poll on.
Yeah sounds neater. It has the slight drawback that it may not work
for pure i2c buses since it an SMB thing??
BTW, why do you need special treatment for multiple segments? Will it not
simply have an ARA appear on whatever i2c bus the device sits on? And if
something requests to send an ARA message on a bus that happens to be a
muxed segment, my mental picture is that the mux will be operated as usual
so that the ARA appears on the muxed segment. Maybe I'm missing something?
My think was the following.
When the SMBALERT is asserted a ARA needs to be sent by the master.
If the device sending the SMBALERT is behind a mux when need to know which segment of the bus to enable.
Using shared interrupts should work I think, but you have to iterate thru each bus segment.
If the alert device is nested behind a couple of muxes this could get expensive.
But yeah otherwise I think the correct mux segment will get enabled automatically.
The current SMBALERT driver only seems to attached to the root i2c adapter.
But p4-5 could be dropped which is where we're stuck I think.
Yes, I dislike to add a workaround for a specific case that might get
in the way for anybody wishing to fix a bigger, more generic, problem...
Looking at this approach it shouldn't matter if the ltc1760 driver has registered yet or not.
This approach possibly has a lot more generic appeal I think.
Thoughts on just submitting p1-3 for now while I figure out the SMB alert approach?
Yes, looks like a plan. Thanks in advance!
Thanks, I'll do a new version with just p1-3.
- if (!data->irq_mask)
- enable_irq(data->client->irq);
data->irq_mask |= BIT(pos);
+ if (!data->irq_enabled
+ && (data->irq_mask & mask_enable) == mask_enable) {
I think the coding standard says that the && should be at the end of the
first line. Didn't checkpatch complain?
No it didn't complain. and I wasn't sure which way to do this.
Ah, you need the --strict option for that to show up...
Haven't come across that option, I'll give it a try in future.
--
Regards
Phil Reid
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