On Wed, Jan 13, 2010 at 01:56:15AM +0100, Stefan Richter wrote:
> Matthew Garrett wrote:
> > For sanity purposes, the code ensures that the phy is recent enough to
> > implement the required functionality. It also ensures that all ports have
> > the interrupt enabled - a VIA chip I've tested appears to only allow
> > int_enable to be set on one port at a time, which is inadequate for the
> > purposes of this code.
>
> This adds more extensive use of the link--PHY interface than we ever
> had, and FireWire stacks in other popular OSs may not have used these
> features yet too. We will most certainly discover further errata
> besides the one that you already found.
I don't doubt it. There's almost certainly serious dragons here on some
hardware.
> > This depends on the PCI runtime PM code, which is not yet upstream. I'm
> > sending this out now for sanity checking.
>
> Is there a convenient source where I can get the infrastructure, so that
> I could start testing with the few cards that I have?
Rafael posted the latest set to linux-acpi on the 27th of December. I
don't think there's a set online yet.
> Besides the danger of regressions due to hardware bugs, there is also
> the cost in terms of code footprint. Therefore it would be very good if
> measurements of actual effects on energy consumption could be obtained.
Sure. I'll try to do the measurements today.
> >
> > reg_write(ohci, OHCI1394_PhyControl, OHCI1394_PhyControl_Read(addr));
>
> ...the read and write "transactions" on OHCI1394_PhyControl need to be
> serialized with a lock or mutex now. This means the simple read/ write
> operations and also the combined read--update operations or combined
> page-select--read-page operations.
>
> (Of course your implementation requires a spinlock rather than a mutex,
> for now.)
Right. I'll add that.
> > + for (i = 0; i < OHCI_LOOP_COUNT; i++) {
> > + *val = reg_read(ohci, OHCI1394_PhyControl);
> > + if (*val & OHCI1394_PhyControl_ReadDone)
> > + break;
> > + mdelay(1);
> > + }
>
> Gone is the msleep, here comes the mdelay. I suspect all that can be
> implemented in a non-atomic context, can't it? I.e. tasklet ->
> worklet... May possibly require to convert the bus reset tasklet to a
> worklet too, which may have a few benefits on its own right.
Yeah, that might well be a bonus. The phy accesses should only be at
startup or in response to a bus reset or cable connection state change,
so I wouldn't have thought that there'd be any noticable performance
impact. I'll look at changing it in a followup patch.
> Furthermore, these polling loops --- at least the ones after a
> reg_write(..., OHCI1394_PhyControl_Read(..)) --- could then be replaced
> by an interrupt driven mechanism. (Except in those usages of
> ohci_update_phy_reg() when we do not have interrupts enabled.)
Oh, ok - I hadn't realised there was an interrupt to indicate that.
> On OHCI_LOOP_COUNT: Don't use this one. IMO this is only obuscation.
> Its current single use in firewire-ohci should be eliminated as well,
> and that one is unrelated to PHY control. And even the new PHY control
> related loops may perhaps want different loop counts.
>
> Furthermore, 500 times mdelay(1) as worst case sounds suboptimal. If
> this is converted into nonatomic context, timeouts this large will be
> more acceptable.
This was just copied from the old ieee1394 ohci code when I was seeing
some odd phy behaviour. I've since worked out that this was due to me
misunderstanding the specs, so I suspect it'd work fine with the old
code (well, s/sleep/delay/).
> > + OHCI1394_PhyControl_Write(addr, r));
> > +
> > + for (i = 0; i < OHCI_LOOP_COUNT; i++) {
> > + r = reg_read(ohci, OHCI1394_PhyControl);
> > + if (!(r & OHCI1394_PhyControl_WriteDone))
> > + break;
> > + }
>
> Forgot an mdelay?
I wondered about that, but there wasn't one in the ieee1394 code.
Presumably the register reads take long enough that it settles within
the loop count?
> > + for (i = 0; i < total_ports; i++) {
> > + ohci_read_port_reg(card, i, 0, &val);
> > + if (val & 0x04)
> > + return 1;
> > + }
> > +
> > + return 0;
> > +}
>
> This is a somewhat costly check. Its two call sites should be examined
> whether there is other information available that tells us whether ports
> are connected. For example...
It's certainly not entirely optimal.
> > +out:
> > + if (!ohci_port_is_connected(&ohci->card))
> > + pm_schedule_suspend(ohci->card.device, 1000);
> > +
> > + return;
> > }
>
> ...if we have a valid self ID buffer here, and if we previously
> determined how many self IDs the local PHY itself generates (in practice
> only one, in theory up to three), then we can cheaply check by means of
> self_id_count whether anything is attached.
And if we don't, we fall back to the check? That'd work.
> [BTW, some cards may actually have a second PHY hardwired to the PHY
> which is attached to the link. For example, Mac Pro have a second PHY
> for the front panel ports. But your approach is unable to figure that
> out either. And it doesn't matter because battery powered devices do
> not have more than one PHY per link.]
Hrm. That's potentially a problem. Will this always show up as a
connection being present on the first PHY? If so it'll just effectively
disable the power management, which isn't ideal but at least doesn't
break anything.
> > +
> > + if (ohci_read_phy_reg(card, 2, &val))
> > + return -EBUSY;
>
> Since its caller does not check for error return,
> ohci_configure_wakeup() can just return void.
Hm. Should probably actually check the return value instead.
> > OHCI1394_cycle64Seconds | OHCI1394_regAccessFail |
> > - OHCI1394_masterIntEnable);
> > + OHCI1394_masterIntEnable | OHCI1394_phy);
>
> This warrants a little addition in our goophy debug logging section, see
> log_irqs() at the top pf ohci.c.
Ok.
> > reg_write(ohci, OHCI1394_ConfigROMhdr, 0);
> > +
> > reg_write(ohci, OHCI1394_BusOptions,
> > be32_to_cpu(ohci->next_config_rom[2]));
> > reg_write(ohci, OHCI1394_ConfigROMmap, ohci->next_config_rom_bus);
>
> What's this blank line for? :-)
Oops - left over from debug code.
> > + .poweroff = ohci_pci_suspend,
> > + .runtime_suspend = ohci_pci_runtime_suspend,
> > + .runtime_resume = ohci_pci_resume,
> > + .runtime_idle = ohci_pci_runtime_idle,
> > +};
>
> Obligatory whitespace nitpick :-) --- Look how nicely krh aligned his code:
Heh, ok.
> Thanks for working on this. Considering how often FireWire equipped
> notebooks are used with the 1394 drivers loaded but the port unused all
> day, this may be a worthwile enhancement.
Yeah, I realised that working on this is the first time I've ever
plugged a firewire cable into anything...
--
Matthew Garrett | mjg59@xxxxxxxxxxxxx
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