Messages in this thread | | | Subject | Re: pci error recovery procedure | From | "Zhang, Yanmin" <> | Date | Fri, 01 Sep 2006 17:04:09 +0800 |
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On Fri, 2006-09-01 at 11:42, Zhang, Yanmin wrote: > On Fri, 2006-09-01 at 01:50, Linas Vepstas wrote: > > On Thu, Aug 31, 2006 at 03:10:12PM +0800, Zhang, Yanmin wrote: > > > Linas, > > > > > > I am reviewing the error handlers of e1000 driver and got some ideas. My > > > startpoint is to simplify the err handler implementations for drivers, or > > > driver developers are *not willing* to add it if it's too complicated. > > > > I don't see that its to complicated ... > Originally, I didn't think so, but after I try to add err_handlers to some > drivers, I feel it's too complicated. > > > > > > 1) Callback mmio_enabled looks useless. Documentation/pci-error-recovery.txt > > > says the current powerpc implementation does not implement this callback. > > > > I don't know if its useless or not. I have not needed it yet for the > > symbios, ipr and e1000 drivers, but its possible that some more > > sophisticated device may want it. I'm tempted to keep it a while > > longer befoe discarding it. > > > > The scenario is this: the device driver decides that, rather than asking > > for a full electical reset of the card, instead, it wants to perform > > its own recovery. It can do this as follows: > > > > a) enable MMIO > > b) issue reset command to adapter > > c) enable DMA. > > > > If we enabled both DMA and MMIO at the same time, there are mnay cases > > where the card will immediately trap again -- for example, if its > > DMA'ing to some crazy address. Thus, typically, one wants DMA disabled > > until after the card reset. Withouth the mmio_enabled() reset, there > > is no way of doing this. > The new error_resume, or the old slot_reset could take care of it. The specific > device driver knows all the details about how to initiate the devices. The > error_resume could call the step a) b) c) sequencially while doing checking among > steps. > > If there is really a device having specific requirement to reinitiate it (very rarely), > it could use walkaround, such like schedule a WORKER. No need to provide a generic > mmio_enabled. > > > > > > 2) Callback slot_reset could be merged with resume. The new resume could be: > > > int (*error_resume)(struct pci_dev *dev); I checked e1000 and e100 drivers and > > > think there is no actual reason to have both slot_reset and resume. > > > > The idea here was to handle multi-function cards. On a multi-function card, > > *all* devices need to indicate that they were able to reset. Once all devices > > have been successfuly reset, then operation can be resumed. If the reset > > of one function fails, then operation is not resumed for any f the > > functions. > I don't think we need slot_reset to coordinate multi-function devices. The new > error_resume could take care of multi-function card. 'reset' here means driver > need do I/O to detect if the device (function) still works well. If a function > of a multi-function device couldn't reset while other functions could reset, > other functions could just go on to reinitiate. In the end, the error recovery > procedure (handle_eeh_events in PowerPC implementation) could check all the > returning values of error_resume. If there is a failure value, then removes > all the functions' pci_dev of the device from the bus. > > > > > > 3) link_reset is not used in pci express aer implementation, so it could be > > > deleted also. > > > > OK. Link reset was added explicitly to support PCI-E, so if its not wanted, > > we can eliminate it. > > > > > How did you test e1000 err_handler? > > > > We have three methods (I thought these were documented). In one, a > > technician brushes a grounding strap to some of the signal pins. > > In the second, slots are populated with known-bad cards. The third test > > involes sending a command down to the pci bridge chip, telling it to > > behave as if it detected an error. For development, the last is > > quick-n-easy. > Thanks for your explanation. > > > > > > In the simulated enviroment, the testing might be > > > incorrect. > > > > Why would it be incorrect? I mean, we don't simulate having someone pour a > > cup of coffee into the guts of the machine ... but my understanding is > > the machines do get standard vibration/thermal/humidity testing, which > > is good enough for me. > > > > > For example, e1000_io_error_detected would call e1000_down to reset NIC. > > > > Why would that be incorrect? > > > > > During > > > our last discussion on LKML, you said PowerPC will block further I/O if the platform captures > > > a pci error, so the all I/O in e1000_down will be blocked. Later on, e1000_io_slot_reset > > > will reenable pci device and initiate NIC. I guess late initiate might fail because prior > > > e1000_down I/O don't reach NIC. > > > > Why would it fail? The e1000_down serves primarily to get the Linux > > kernel into a known state. It doesn't matter what happens to the card, > > since the next step will be to perform an electrical reset of the card. > Who will perform the electrical reset of the card? Function e1000_reset or the platform? > If it's the platform, I agree with you, but if it's e1000_reset, it might not work because > e1000_reset uses a e1000-specific approach to reset the card. I'm not sure if the e1000_reset > will restore the NIC to fresh system power-on state. At least, from the source codes, e1000_reset > couldn't. One more comment: The second parameter of error_detected also could be deleted because recovery procedures will save error to pci_dev->error_state.
So, the err_handler pci_error_handlers could be: struct pci_error_handlers { pci_ers_result_t (*error_detected)(struct pci_dev *dev); pci_ers_result_t (*error_resume)(struct pci_dev *dev); };
Yanmin - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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