[+cc David] On Tue, Jan 17, 2017 at 09:02:58PM +0000, Russell King - ARM Linux wrote: > On Tue, Jan 17, 2017 at 07:34:14PM +0000, Russell King - ARM Linux wrote: > > Uwe, can you try: > > > > setpci -s <whatever-the-id-of-the-root-is-it's-blanked-out-in-the-above> \ > > 0x50.w=0x60 > > > > and see whether it remains alive (you can check by reading the root > > register 0x52.w - bit 12 should be set once bit 11 clears again. > > For reference, this I got wrong... > > 0xf1041a04 bit 0 indicates link status (0 = link up, 1 = link down). > > > If that's successful, maybe setting the common clock bit on the PCIe > > device is what's causing the problem, in which case: > > > > setpci -s 02:00.0 0x80.w=0x40 > > setpci -s <whatever-the-id-of-the-root-is-it's-blanked-out-in-the-above> \ > > 0x50.w=0x60 > > Having worked with Uwe over IRC, it seems that any request to retrain > causes the link to go down, either with or without the common clock bit > set: > > # setpci -s 2.0 0x50.w=0x60 > # setpci -s 2.0 0x52.w > 0011 > # memtool md 0xf1041a04+4 > f1041a04: 00010201 > ... reboot ... > # setpci -s 2.0 0x50.w=0x20 > # memtool md 0xf1041a04+4 > f1041a04: 00010201 > > which doesn't point towards ASPM itself, but the problem is caused by > a side effect of ASPM's setup code which always triggers a retrain. > > Bit 5 in that register is documented (at least in the Armada 370 docs > and Armada XP docs I have) as: > > 5 RetrnLnk RW Retrain Link > 0x0 This bit forces the device to initiate link retraining. > Always returns 0 when read. > NOTE: If configured as an Endpoint, this field is > reserved and has no effect. > > Bjorn, are you aware of similar situations where a request for the PCIe > link to be retrained causes it to fail? The only one that comes to mind is this patch from David (CC'd) that avoids ASPM-related retrains when we know the link doesn't support ASPM: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=e53f9a28bee3 Side note: it looks like we don't use the recommended retrain algorithm in the implementation note about avoiding race conditions in PCIe r3.0, sec 7.8.7. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
