[PATCH v2] PCI: dw-rockchip: Enable L0S capability

[Shawn Lin]

L0S capability isn't enabled on all SoCs by default, so enabling it
in order to make ASPM L0S work on Rockchip platforms. We have been
testing it for quite a long time and found the default FTS number
provided by DWC core doesn't work stable and make LTSSM switch between
L0S and Recovery, leading to long exit latency, even fail to link sometimes.
So override it to the max 255 which seems work fine under test for both PHYs
used by Rockchip platforms.

Signed-off-by: Shawn Lin <shawn.lin at rock-chips.com>
---

Changes in v2:
- Move n_fts to probe function
- rewrite the commit message

 drivers/pci/controller/dwc/pcie-dw-rockchip.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-dw-rockchip.c b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
index 21dc99c..c397f3a 100644
--- a/drivers/pci/controller/dwc/pcie-dw-rockchip.c
+++ b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
@@ -185,6 +185,17 @@ static int rockchip_pcie_link_up(struct dw_pcie *pci)
 static int rockchip_pcie_start_link(struct dw_pcie *pci)
 {
 	struct rockchip_pcie *rockchip = to_rockchip_pcie(pci);
+	u32 cap, lnkcap;
+
+	/* Enable L0S capability for all SoCs */
+	cap = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
+	if (cap) {
+		lnkcap = dw_pcie_readl_dbi(pci, cap + PCI_EXP_LNKCAP);
+		lnkcap |= PCI_EXP_LNKCAP_ASPM_L0S;
+		dw_pcie_dbi_ro_wr_en(pci);
+		dw_pcie_writel_dbi(pci, cap + PCI_EXP_LNKCAP, lnkcap);
+		dw_pcie_dbi_ro_wr_dis(pci);
+	}
 
 	/* Reset device */
 	gpiod_set_value_cansleep(rockchip->rst_gpio, 0);
@@ -598,6 +609,9 @@ static int rockchip_pcie_probe(struct platform_device *pdev)
 	rockchip->pci.dev = dev;
 	rockchip->pci.ops = &dw_pcie_ops;
 	rockchip->data = data;
+	/* Default fts number(210) is broken, override it to 255 */
+	rockchip->pci.n_fts[0] = 255; /* Gen1 */
+	rockchip->pci.n_fts[1] = 255; /* Gen2+ */
 
 	ret = rockchip_pcie_resource_get(pdev, rockchip);
 	if (ret)
-- 
2.7.4