Re: [PATCH] synchronize_irq needs a barrier

On Saturday 20 October 2007 07:04:35 Benjamin Herrenschmidt wrote:

quoted

1) some drivers use pci_disable_device(), and pci_enable_device().
should I use it too?

I generally don't do the former, and I would expect the late to be done
by pci_restore_state() for you. pci_disable_device(), last I looked,
only cleared the bus master bit though, which might be a good idea to
do.

People in ACPI/x86 land, are there more good reasons to do one or the
other ?

That reminds me that I volunteered to write a documentation on how
drivers should do all that stuff at KS and didn't get to actually doing
it yet. shame ... I'll try to start something asap.

quoted

2) I accidentally did this:
	pci_set_power_state(pci_dev, pci_choose_state(pci_dev, state));
	pci_save_state(pci_dev);

I somehow thought that this is correct, that I should save the pci config state
after the power-down, but now I know that it isn't correct.

Right, you need to do the save_state before the power down. You need to
avoid pretty much any access to the device after the save state other
than the pending set_power_state on resume.

quoted

I now need to send a patch for dmfe.c network driver that has the same commands written by me.
(but it works perfectly anyway)

On x86 desktop... might have surprises on others.

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Is it possible to access pci configuration space in D3?

It's only really safe to access the PM register itself, though I suppose
you should be able to walk the capability chain to do that. But I
wouldnt recommend doing anything else.

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And lastly speaking of network drivers, one issue came to my mind:
most network drivars has a packet queue and in case of dmfe it is located in main memory,
and card does dma from it.

Note that the network stack nowadays does a fair bit of cleaning up for
you before your suspend routine is called....

quoted

in .suspend I ignore that some packets may be in that queue, and I want
to ask, whenever there are better ways to do that.


this is my dmfe .suspend routine.

	/* Disable upper layer interface */
	netif_device_detach(dev);

Looks allright on a quick glance appart from the bits we already
discussed.

quoted

I guess, everybody makes mistakes... :-)

Other network drivers has a bit more complicated .suspend/.resume routines, 
but I didn't see a driver waiting for output queue to finish

I think the network stack does that nowadays but we'll have to double
check, that's based on what DaveM told me at KS.

Ben. 

Hi,

Thanks a lot.
I fix the order of calls in dmfe.c
and in saa7134-core.c.

I probably need to add this synchronize_irq() logic in dmfe.c too, but I probably do it later,
I think I am overestimating this race, since most drivers don't do dev->insuspend checks in IRQ handler.
Maybe even just use free_irq() after all....


Best regards,
	Maxim Levitsky