| Message ID | 20250506073934.433176-8-cassel@kernel.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | PCI: dwc: Link Up IRQ fixes | expand |
On Tuesday, May 6th, 2025 at 9:39 AM, Niklas Cassel <cassel@kernel.org> wrote: > Commit 36971d6c5a9a ("PCI: qcom: Don't wait for link if we can detect Link > Up") changed so that we no longer call dw_pcie_wait_for_link(), and instead > enumerate the bus when receiving a Link Up IRQ. > > Before 36971d6c5a9a, we called dw_pcie_wait_for_link(), and in the first > iteration of the loop, the link will never be up (because the link was just > started), dw_pcie_wait_for_link() will then sleep for LINK_WAIT_SLEEP_MS > (90 ms), before trying again. > > This means that even if a driver was missing a msleep(PCIE_T_RRS_READY_MS) > (100 ms), because of the call to dw_pcie_wait_for_link(), enumerating the > bus would essentially be delayed by that time anyway (because of the sleep > LINK_WAIT_SLEEP_MS (90 ms)). > > While we could add the msleep(PCIE_T_RRS_READY_MS) after deasserting PERST > (qcom already has an unconditional 1 ms sleep after deasserting PERST), > that would essentially bring back an unconditional delay during probe (the > whole reason to use a Link Up IRQ was to avoid an unconditional delay > during probe). > > Thus, add the msleep(PCIE_T_RRS_READY_MS) before enumerating the bus in the > IRQ handler. This way, for qcom SoCs that has a link up IRQ, we will not > have a 100 ms unconditional delay during boot for unpopulated PCIe slots. > > Fixes: 36971d6c5a9a ("PCI: qcom: Don't wait for link if we can detect Link Up") > Signed-off-by: Niklas Cassel cassel@kernel.org > > --- > drivers/pci/controller/dwc/pcie-qcom.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c > index dc98ae63362d..01a60d1f372a 100644 > --- a/drivers/pci/controller/dwc/pcie-qcom.c > +++ b/drivers/pci/controller/dwc/pcie-qcom.c > @@ -1565,6 +1565,7 @@ static irqreturn_t qcom_pcie_global_irq_thread(int irq, void data) > > if (FIELD_GET(PARF_INT_ALL_LINK_UP, status)) { > dev_dbg(dev, "Received Link up event. Starting enumeration!\n"); > + msleep(PCIE_T_RRS_READY_MS); > / Rescan the bus to enumerate endpoint devices */ > pci_lock_rescan_remove(); > pci_rescan_bus(pp->bridge->bus); > > -- > 2.49.0 Tested-by: Laszlo Fiat <laszlo.fiat@proton.me>
diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c index dc98ae63362d..01a60d1f372a 100644 --- a/drivers/pci/controller/dwc/pcie-qcom.c +++ b/drivers/pci/controller/dwc/pcie-qcom.c @@ -1565,6 +1565,7 @@ static irqreturn_t qcom_pcie_global_irq_thread(int irq, void *data) if (FIELD_GET(PARF_INT_ALL_LINK_UP, status)) { dev_dbg(dev, "Received Link up event. Starting enumeration!\n"); + msleep(PCIE_T_RRS_READY_MS); /* Rescan the bus to enumerate endpoint devices */ pci_lock_rescan_remove(); pci_rescan_bus(pp->bridge->bus);
Commit 36971d6c5a9a ("PCI: qcom: Don't wait for link if we can detect Link Up") changed so that we no longer call dw_pcie_wait_for_link(), and instead enumerate the bus when receiving a Link Up IRQ. Before 36971d6c5a9a, we called dw_pcie_wait_for_link(), and in the first iteration of the loop, the link will never be up (because the link was just started), dw_pcie_wait_for_link() will then sleep for LINK_WAIT_SLEEP_MS (90 ms), before trying again. This means that even if a driver was missing a msleep(PCIE_T_RRS_READY_MS) (100 ms), because of the call to dw_pcie_wait_for_link(), enumerating the bus would essentially be delayed by that time anyway (because of the sleep LINK_WAIT_SLEEP_MS (90 ms)). While we could add the msleep(PCIE_T_RRS_READY_MS) after deasserting PERST (qcom already has an unconditional 1 ms sleep after deasserting PERST), that would essentially bring back an unconditional delay during probe (the whole reason to use a Link Up IRQ was to avoid an unconditional delay during probe). Thus, add the msleep(PCIE_T_RRS_READY_MS) before enumerating the bus in the IRQ handler. This way, for qcom SoCs that has a link up IRQ, we will not have a 100 ms unconditional delay during boot for unpopulated PCIe slots. Fixes: 36971d6c5a9a ("PCI: qcom: Don't wait for link if we can detect Link Up") Signed-off-by: Niklas Cassel <cassel@kernel.org> --- drivers/pci/controller/dwc/pcie-qcom.c | 1 + 1 file changed, 1 insertion(+)