On Fri, Sep 16, 2022 at 06:23:02PM +0200, Marek Behún wrote: > On Fri, 9 Sep 2022 16:57:11 +0200 > Lorenzo Pieralisi <lpieralisi@xxxxxxxxxx> wrote: > > > [+Marc, Thomas - I can't merge this code without them reviewing it, > > I am not sure at all you can mix the timer/IRQ code the way you do] > > > > On Thu, Aug 18, 2022 at 03:51:32PM +0200, Marek Behún wrote: > > > From: Pali Rohár <pali@xxxxxxxxxx> > > > > > > Add support for Data Link Layer State Change in the emulated slot > > > registers and hotplug interrupt via the emulated root bridge. > > > > > > This is mainly useful for when an error causes link down event. With > > > this change, drivers can try recovery. > > > > > > Link down state change can be implemented because Aardvark supports Link > > > Down event interrupt. Use it for signaling that Data Link Layer Link is > > > not active anymore via Hot-Plug Interrupt on emulated root bridge. > > > > > > Link up interrupt is not available on Aardvark, but we check for whether > > > link is up in the advk_pcie_link_up() function. By triggering Hot-Plug > > > Interrupt from this function we achieve Link up event, so long as the > > > function is called (which it is after probe and when rescanning). > > > Although it is not ideal, it is better than nothing. > > > > So before even coming to the code review: this patch does two things. > > > > 1) It adds support for handling the Link down state > > 2) It adds some code to emulate a Link-up event > > > > Now, for (2). IIUC you are adding code to make sure that an HP > > event is triggered if advk_pcie_link_up() is called and it > > detects a Link-down->Link-up transition, that has to be notified > > through an HP event. > > > > If that's correct, you have to explain to me please what this is > > actually achieving and a specific scenario where we want this to be > > implemented, in fine details; then we add it to the commit log. > > Hello Lorenzo, sorry for not replying earlier. > > Would something like this be sufficient? > > DLLSC is needed by the pciehp driver, which handles hotplug, but also > link state change events. AFAIK no Aardvark devices support hotplug, > but link state change events are required for graceful driver > unbinding in case of link down event. > > So with this change we achieve graceful driver unbind for example > when WiFi card PCIe link goes down (we've seen this with ath10k and > mt76 WiFi cards). Before the WiFi driver started spitting out errors, > or even taking the whole system down. > > Since after link goes down, it can come back up if the WiFi card can > recover (or if reset pin is used to reset the card), we need to be > able to recognize link up event. Since AFAIK Aardvark does not have > interrupt for link up event, the best thing we can do is simulate it > - whenever we read the link state, find it is up, and have cached > value saying it is down, we trigger the link up event. We read link > state whenever the configuration space is read, for example by > writing 1 to /sys/bus/pci/rescan. Better, certainly. Question, also related to Marc's query. Do you rely on the hotplug (emulated IRQ) to be run _before_ carrying on with PCI config space accesses following a link-up detection ? How was the jiffies + 1 expiration time determined ? I assume you want to run the emulated HP IRQ asap - the question though is how fast should it be ? Lorenzo > > Marek > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
