PCI: dw-rockchip: Enable ASPM L0s capability for both RC and EP modes

L0s capability isn't enabled on all Rockchip SoCs by default, so enable it
in order to make ASPM L0s work on Rockchip platforms.

Testing the L0s for a long time revealed that the default N_FTS value of
210 in the hardware doesn't work stable and causes LTSSM to switch between
L0s and Recovery states. This leads to long exit latency and also causes
link down sometimes. So override the value to the max 255, which seems to
work fine under both PHYs used on Rockchip platforms.

Signed-off-by: Shawn Lin <[email protected]>
[mani: subject and description rewording]
Signed-off-by: Manivannan Sadhasivam <[email protected]>
Reviewed-by: Niklas Cassel <[email protected]>
Reviewed-by: Manivannan Sadhasivam <[email protected]>
Link: https://patch.msgid.link/[email protected]

Author: shawn1221

drivers/pci/controller/dwc/pcie-dw-rockchip.c

@@ -182,6 +182,21 @@ static int rockchip_pcie_link_up(struct dw_pcie *pci)
 	return 0;
 }
 
+static void rockchip_pcie_enable_l0s(struct dw_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);
+	}
+}
+
 static int rockchip_pcie_start_link(struct dw_pcie *pci)
 {
 	struct rockchip_pcie *rockchip = to_rockchip_pcie(pci);
@@ -231,6 +246,8 @@ static int rockchip_pcie_host_init(struct dw_pcie_rp *pp)
 	irq_set_chained_handler_and_data(irq, rockchip_pcie_intx_handler,
 					 rockchip);
 
+	rockchip_pcie_enable_l0s(pci);
+
 	return 0;
 }
 
@@ -271,6 +288,8 @@ static void rockchip_pcie_ep_init(struct dw_pcie_ep *ep)
 	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
 	enum pci_barno bar;
 
+	rockchip_pcie_enable_l0s(pci);
+
 	for (bar = 0; bar < PCI_STD_NUM_BARS; bar++)
 		dw_pcie_ep_reset_bar(pci, bar);
 };
@@ -599,6 +618,10 @@ static int rockchip_pcie_probe(struct platform_device *pdev)
 	rockchip->pci.ops = &dw_pcie_ops;
 	rockchip->data = data;
 
+	/* Default N_FTS value (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)
 		return ret;