On Tue, May 24, 2016 at 10:42:31AM -0400, Sinan Kaya wrote: > On 5/24/2016 7:53 AM, Bjorn Helgaas wrote: > > On Tue, May 24, 2016 at 06:29:44AM +0000, Ocean HY1 He wrote: > >> > In pcie_config_aspm_link(), when convert ASPM state to > >> > upstream/downstream ASPM register state, the upstream variable and > >> > dwsream variable are reversed. This causes PCI/E link enter ASPM L0s > >> > even it should be disabled and PCI/E endpoint may reset randomly. > > Random resets of an endpoint sounds like a pretty bad problem. Do you > > have a bug report? We've had lots of issues with ASPM; I wonder if > > this could account for some of them. > > I'm seeing this problem on Linux's ASPM code using powersave option where > each side of the link is having ASPM L0s enabled without coordination with > the other side. I'm wondering if you are hitting this too. This would be really bad. Can you fill in a few more details about how this happens? I thought you were talking about booting with "pcie_aspm.policy=powersave", where pcie_aspm_set_policy() sets aspm_policy = POLICY_POWERSAVE, then configures each link with ASPM_STATE_ALL. But pcie_config_aspm_link() does AND the desired state (ASPM_STATE_ALL) with link->aspm_capable, which only has ASPM_STATE_L0S set if both the upstream and downstream components advertised PCIE_LINK_STATE_L0S. This path is very complicated, but I don't *think* it will enable L0s if the other end of the link doesn't support it. > Legacy software (either operating system or firmware) that encounters > the previously reserved value 00b (No ASPM Support), will most likely > refrain from enabling L1, which is intended behavior. 10 Legacy software > will also most likely refrain from enabling L0s for that component’s > Transmitter (also intended behavior), but it is unclear if such software > will also refrain from enabling L0s for the component on the other side > of the Link. > > If software enables L0s on one side when the component on > the other side does not indicate that it supports L0s, the result is > undefined. -- 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
