PCI: mobiveil: ls_pcie_g4: add Workaround for A-011451

When LX2 PCIe controller is sending multiple split completions and
ACK latency expires indicating that ACK should be send at priority.
But because of large number of split completions and FC update DLLP,
the controller does not give priority to ACK transmission. This
results into ACK latency timer timeout error at the link partner and
the pending TLPs are replayed by the link partner again.

Workaround:
1. Reduce the ACK latency timeout value to a very small value.
2. Restrict the number of completions from the LX2 PCIe controller
   to 1, by changing the Max Read Request Size (MRRS) of link partner
   to the same value as Max Packet size (MPS).

This patch implemented part 1, the part 2 can be set by kernel parameter
'pci=pcie_bus_perf'

This ERRATA is only for LX2160A Rev1.0, and it will be fixed
in Rev2.0.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
[fixed up for mainline -- rmk]
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 15 insertions, 0 deletions

diff --git a/drivers/pci/controller/mobiveil/pcie-layerscape-gen4.c b/drivers/pci/controller/mobiveil/pcie-layerscape-gen4.c
index 43dede26cc7c..d07cddb9c404 100644
--- a/drivers/pci/controller/mobiveil/pcie-layerscape-gen4.c
+++ b/drivers/pci/controller/mobiveil/pcie-layerscape-gen4.c
@@ -81,12 +81,27 @@ static bool ls_g4_pcie_is_bridge(struct ls_g4_pcie *pcie)
 	return header_type == PCI_HEADER_TYPE_BRIDGE;
 }
 
+static void workaround_A011451(struct ls_g4_pcie *pcie)
+{
+	struct mobiveil_pcie *mv_pci = &pcie->pci;
+	u32 val;
+
+	/* Set ACK latency timeout */
+	val = mobiveil_csr_readl(mv_pci, GPEX_ACK_REPLAY_TO);
+	val &= ~(ACK_LAT_TO_VAL_MASK << ACK_LAT_TO_VAL_SHIFT);
+	val |= (4 << ACK_LAT_TO_VAL_SHIFT);
+	mobiveil_csr_writel(mv_pci, val, GPEX_ACK_REPLAY_TO);
+}
+
 static int ls_g4_pcie_host_init(struct mobiveil_pcie *pci)
 {
 	struct ls_g4_pcie *pcie = to_ls_g4_pcie(pci);
 
 	pcie->rev = mobiveil_csr_readb(pci, PCI_REVISION_ID);
 
+	if (pcie->rev == REV_1_0)
+		workaround_A011451(pcie);
+
 	return 0;
 }