PCI: brcmstb: Wait for 100ms following PERST# deassert

commit 3ae140a upstream. Be prudent and give some time for power and clocks to become stable. As described in the PCIe CEM specification sections 2.2 and 2.2.1; as well as PCIe r5.0, 6.6.1. Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Jim Quinlan <[email protected]> Signed-off-by: Lorenzo Pieralisi <[email protected]> Acked-by: Florian Fainelli <[email protected]>
kdoren · Sep 19, 2023 · 6f634d7 · 6f634d7
1 parent e079555
commit 6f634d7
Showing 1 changed file with 9 additions and 2 deletions.
diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
@@ -1038,8 +1038,15 @@ static int brcm_pcie_start_link(struct brcm_pcie *pcie)
 	pcie->perst_set(pcie, 0);
 
 	/*
-	 * Give the RC/EP time to wake up, before trying to configure RC.
-	 * Intermittently check status for link-up, up to a total of 100ms.
+	 * Wait for 100ms after PERST# deassertion; see PCIe CEM specification
+	 * sections 2.2, PCIe r5.0, 6.6.1.
+	 */
+	msleep(100);
+
+	/*
+	 * Give the RC/EP even more time to wake up, before trying to
+	 * configure RC.  Intermittently check status for link-up, up to a
+	 * total of 100ms.
 	 */
 	for (i = 0; i < 100 && !brcm_pcie_link_up(pcie); i += 5)
 		msleep(5);