[PATCH 1/1] PCI/ASPM: Add a fix for an erratum of the PI7C9X111SLB PCI-to-PCIe bridge

["Stefan Mätje" <stefan.maetje@esd.eu>]

Due to an erratum in the Pericom PI7C9X111SLB bridge in reverse mode the
retrain link bit needs to be cleared again manually to allow the link
training to succeed.

If it is not cleared manually the link training is continuously restarted
and all devices below the PCI-to-PCIe bridge can't be accessed any more.
That means drivers for devices below the bridge will be loaded but won't
work or even crash because the driver is only reading 0xffff.

See also the Pericom Errata Sheet PI7C9X111SLB_errata_rev1.2_102711.pdf.

Signed-off-by: Stefan Mätje <stefan.maetje@esd.eu>
---
 drivers/pci/pcie/aspm.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 5326916715d2..89a245023aa9 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -268,6 +268,15 @@ static void pcie_aspm_configure_common_clock(struct pcie_link_state *link)
 	/* Retrain link */
 	reg16 |= PCI_EXP_LNKCTL_RL;
 	pcie_capability_write_word(parent, PCI_EXP_LNKCTL, reg16);
+	if (0x12d8 == parent->vendor && 0xe111 == parent->device) {
+		/*
+		 * Due to an erratum in the Pericom PI7C9X111SLB bridge in
+		 * reverse mode the retrain link bit needs to be cleared
+		 * again manually to allow the link training to succeed.
+		 */
+		reg16 &= ~PCI_EXP_LNKCTL_RL;
+		pcie_capability_write_word(parent, PCI_EXP_LNKCTL, reg16);
+	}
 
 	/* Wait for link training end. Break out after waiting for timeout */
 	start_jiffies = jiffies;
-- 
2.15.0