On Fri, Jul 26, 2019 at 10:15:24AM -0600, Keith Busch wrote: > On Fri, Jul 26, 2019 at 02:00:05AM -0700, Patel, Mayurkumar wrote: > > > The call to pci_save_state most likely occurs long before a user has an > > > opportunity to alter these regsiters, though. Won't this just restore > > > what was previously there, and not the state you changed it to? > > > > There were two things (not sure to call them issues), > > 1. PCI_ERR_ROOT_COMMAND resets to 0 during S3 entry/exit, which disables AER interrupt trigger > > if AER happens on Endpoint after resume. > > > > Also specified in spec. NCB-PCI_Express_Base_4.0r1.0_September-27-2017-c.pdf in > > chapter 7.8.4.9 Root Error Command Register (Offset 2Ch) - in bitfields descriptions. > > i.e. Correctable Error Reporting Enable – When Set, this bit enables the generation of an interrupt when > > a correctable error is reported by any of the Functions in the Hierarchy Domain associated with this Root Port. > > > > 2. Root port resets to its default configuration of UNCOR_MASK/SEVER/COR_MASK register bits after system resume. > > This influences user configurations, how errors shall be treated if AER happens on root port itself due to Device (for example > > Endpoint not answering which results in completion timeouts on root ports). > > > > Following is one example scenario which can handled with this patch. > > - user configures AER registers using setpci certain masks and severity based on debug requirements. This can be applied on Root port of EP. > > - triggers system test which includes S3 entry/exit cycles. > > - system enters s3 -> AER registers settings are saved which has been configured by users. > > - system exits s3 -> AER registers settings are restored which has been configured by users. > > Right, I was just more curious *where* the aer state was being saved > during suspend since pci port driver only saves state during probe. This > patch must be relying on the generic pci-driver's power management. I > think that works, but I just didn't realize initially that we're relying > on that path. I agree that we should save the AER state at suspend-time, not just at probe-time. I *think* this should happen already via the pci_save_state() calls in pci_pm_suspend_noirq(), etc. > > > You are allocating the capability save buffer in aer_probe(), so this > > > save/restore applies only to root ports. But you mention above that you > > > want to restore end devices, right? > > > > That’s correct. I agree that my commit message was not so explicit. > > But Since I included PCI_ERR_ROOT_COMMAND register for save/restore which is specific to Root ports only & I thought > > endpoint drivers can handle to save/restore (UNCOR_MASK/SEVER/COR_MASK) themselves with its suspend/resume functions. > > > > However I am fine to move pci_add_ext_cap_save_buffer() to some other function so > > that it also save/restores UNCOR_MASK/SEVER/COR_MASK registers for endpoints and > > if it's not useful to save/restore MASK & SEVER registers then also fine to remove them > > and just restore PCI_ERR_ROOT_COMMAND & ECRC settings. Please let me know. > > If users are changing default settings that you want to preserve, that > reason should apply to bridges and endpoints too, so I think you ought > to allocate the save buffer for this capability for all devices that > support it in in pci_aer_init(). Just make sure to check the device type > in save/restore so you're not accessing root port specific registers. I agree, I think we need to save/restore AER settings for all devices, not just bridges. Bjorn
