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

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/20221011184211.18128-3-jim2101024@gmail.com
Signed-off-by: Jim Quinlan <jim2101024@gmail.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>

diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
index a45ce7d61847a3f72741b3f62544d473aac24b04..39b545713ba021623dcffdf98be3bf79af833b8e 100644 (file)
--- a/drivers/pci/controller/pcie-brcmstb.c
+++ b/drivers/pci/controller/pcie-brcmstb.c
@@ -1037,8 +1037,15 @@ 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);