On Mon, Jul 4, 2016 at 1:06 PM, dongbo (E) <dongbo4@xxxxxxxxxx> wrote: > On 2016/7/3 23:27, Pratyush Anand wrote: >> On Tue, Jun 28, 2016 at 1:42 PM, dongbo (E) <dongbo4@xxxxxxxxxx> wrote: >>> >>> From: Dong Bo <dongbo4@xxxxxxxxxx> >>> >>> In designware PCIe driver, the iatu0 is used for both CFG and IO accesses. >>> When sending CFGs to peripherals (e.g. lspci), iatu0 frequently switches >>> between CFG and IO alternatively. >>> >>> A MEMORY probably be sent as an IOs by mistake. Considering the following >>> configurations: >>> MEMORY -> BASE_ADDR: 0xb4100000, LIMIT: 0xb4100FFF, TYPE=mem >>> CFG -> BASE_ADDR: 0xb4000000, LIMIT: 0xb4000FFF, TYPE=cfg >>> IO -> BASE_ADDR: 0xFFFFFFFF, LIMIT: 0xFFFFFFFE, TYPE=io >>> >>> Suppose PCIe has just completed a CFG access, to switch back to IO, it set >>> the BASE_ADDR to 0xFFFFFFFF, LIMIT 0xFFFFFFFE and TYPE to io. When another >>> CFG comes, the BASE_ADDR is set to 0xb4000000 to switch to CFG. At this >>> moment, a MEMORY access shows up, since it matches with iatu0 >>> (due to 0xb4000000 <= MEMORY BASE_ADDR <= MEMORY LIMIE <= 0xFFFFFFF), it >>> is treated as an IO access by mistake, then sent to perpheral. >>> >>> This patch fixes the problem by exchanging the assignments of `MEMORYs' >>> and `CFGs/IOs', which assigning MEMEORYs to iatu0, CFGs and IOs to iatu1. >> >> >> Had a re-thought on it. While it will fix wrong memory access in your >> case, it can still cause issues with IO access for some other >> platform. >> >> Can you please test [1] and check it that works for you. You will need >> to define num-viewport in your device tree file. >> >> ~Pratyush >> >> [1] https://github.com/pratyushanand/linux/commit/131b83ea7db0834d77ee5df65c6696bccbf8a1ce >> >> . >> > > Checked, it works for us. Thanks for testing. > > I think it would be better to exchange the assignments of MEMORYs and > CFGs/IOs when num_viewports <= 2, cause it fixes wrong memory access. OK.. I think that can be accommodated. I have rebased your patch on top of mine with some change in commit log. https://github.com/pratyushanand/linux/commit/6d3805a5e0fbbbd73beba80c2c9151b26399ea67 Will send both of the patches to the list for review. > > As you mentioned, other corner point for failure is still there while > there are only two viewports. It seems that there is not a perfect > solution. Yes, unfortunately we will have to live with either remote possibility of less frequent IO transfer corruption or we can disable IO transfer for <=2 viewports. IMHO, former is the better way to go with. ~Pratyush -- 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
