On Mon, Jun 29, 2009 at 04:17:12PM +0800, Kenji Kaneshige wrote: > Shaohua Li wrote: > > On Fri, Jun 26, 2009 at 10:59:20AM +0800, Kenji Kaneshige wrote: > >> Shaohua Li wrote: > >>> On Fri, Jun 19, 2009 at 01:28:44PM +0800, Kenji Kaneshige wrote: > >>>> Shaohua Li wrote: > >>>>> On Fri, Jun 19, 2009 at 11:19:49AM +0800, Kenji Kaneshige wrote: > >>>>>> Shaohua Li wrote: > >>>>>>> On Fri, Jun 19, 2009 at 05:28:41AM +0800, Jesse Barnes wrote: > >>>>>>>> On Thu, 21 May 2009 11:10:06 +0900 > >>>>>>>> Kenji Kaneshige <kaneshige.kenji@xxxxxxxxxxxxxx> wrote: > >>>>>>>> > >>>>>>>>> Hi, > >>>>>>>>> > >>>>>>>>> This patch changes ASPM driver to enable more detailed ASPM > >>>>>>>>> configuration. With this patch, > >>>>>>>>> > >>>>>>>>> - ASPM can be enabled partially in the hierarchy. > >>>>>>>>> - L0s can be managed for each direction (upstream direction and > >>>>>>>>> downstream direction) of the link. > >>>>>>> Well, these are nice features, but what kind of machine does you test? > >>>>>>> Does it have several level hierarchy? The most powerful system I saw > >>>>>>> just has two levels, which sounds not worth adding partial aspm. > >>>>>> Thank you very much for comments. > >>>>>> > >>>>>> I think it is useful also for the system that doesn't have so > >>>>>> many levels of hierarchy, such as mobile systems. Here is "lspci -t" > >>>>>> output on my environment with some comments. My system also has > >>>>>> just two levels, but with the patch, upstream L0s is enabled on the > >>>>>> link 0000:15.00.0 (switch downstream port) to 0000:16:00.0 (endpoint) > >>>>>> in powersave mode. > >>>>> Can you send me the output of lspci -vvvxxx please? > >>>>> > >>>> Here it is. Please note that I'm using pcie_aspm=force option. > >>> Hi, > >>> can you please split the patch into two patches, then I will have more detail > >>> review/test. Also please don't do cleanup in the patches for new feature. > >>> I had a simple look at the patch, and found at least one issue: > >>> A link might have multiple child links, we need check all child links's latency to > >>> enable the parent's ASPM. In pcie_config_aspm_path(), the patch seems not check > >>> peer link. > >>> > >> My understanding is that we can enable parent ASPM even if one > >> or more child links don't meet the latency requirement and ASPM > >> is disabled on them. In this case, parent link will never enter > >> the upstream direction L0s nor L1 state because parent link's > >> downstream component (switch upstream port) never becomes idle. > > Yes, for the case you pointed out, not enabling parent link is always better. > > Why do you think it's better? Because even parent link is enabled, if its child can't enable aspm, the parent link still can't enter aspm. And if parent link isn't enabled, child link can enable aspm. > Doing this (not enabling parent link) would needs complicated > handling and increase the cost very much. yes, it's complicated, but worthy. I thought your partial aspm enabling already handles it well, right? > > Let's take this way: > > 1. always enable downstream's L0s (root port or switch downstream port) > > if downstream device supports L0s. > > If we always enable L0s on downstream port, downstream direction > L0s will be always enabled. Do you mean we don't need to check > latency for downstream direction L0s? please ignore this, we still need check the latency. > > 2. like what you said, enabling endpoint's link if its link meets latency > > requirement but its parent link doesn't. > > I'm sorry but I do not understand the point of your suggestion. > What is the benefit? What do you think about switch upstream ports? Just think your solution is better than always enabling parent link's aspm. > By the way, I'm very sorry for the delay of sending separated > patches. I've already separated the patch into several patches > and compile test has been done. But those are not tested one by > one yet. If it's OK for you, I'll send them before testing. Don't worry about it, not urgent. Thanks, Shaohua -- 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
