[PATCH 2/4] PCI: qcom: Do not enumerate bus before endpoint devices are ready

[Niklas Cassel <cassel@kernel.org>]

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 directly after receiving the Link Up IRQ.

This means that there is no longer any delay between link up and the bus
getting enumerated.

As per PCIe r6.0, sec 6.6.1, a Downstream Port that supports Link speeds
greater than 5.0 GT/s, software must wait a minimum of 100 ms after Link
training completes before sending a Configuration Request.

Add this delay in the threaded link up IRQ handler in order to satisfy
the requirements of the PCIe spec.

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 | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index c789e3f85655..0a627f3b5e2c 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -1565,6 +1565,13 @@ 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");
+		/*
+		 * As per PCIe r6.0, sec 6.6.1, a Downstream Port that supports
+		 * Link speeds greater than 5.0 GT/s, software must wait a
+		 * minimum of 100 ms after Link training completes before
+		 * sending a Configuration Request.
+		 */
+		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