PCI: designware-ep: Disable PTM capabilities for EP mode

Dual mode DesignWare PCIe IP has PTM capability enabled (if supported) even
in the EP mode. The PCIe compliance for the EP mode expects PTM
capabilities (ROOT_CAPABLE, RES_CAPABLE, CLK_GRAN) be disabled.
Hence disable PTM for the EP mode.

Link: https://lore.kernel.org/r/20220919143340.4527-3-vidyas@nvidia.comSigned-off-by: Vidya Sagar <vidyas@nvidia.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Acked-by: Jingoo Han <jingoohan1@gmail.com>

drivers/pci/controller/dwc/pcie-designware-ep.c

@@ -643,7 +643,7 @@ static unsigned int dw_pcie_ep_find_ext_capability(struct dw_pcie *pci, int cap)
 int dw_pcie_ep_init_complete(struct dw_pcie_ep *ep)
 {
 	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
-	unsigned int offset;
+	unsigned int offset, ptm_cap_base;
 	unsigned int nbars;
 	u8 hdr_type;
 	u32 reg;
@@ -659,6 +659,7 @@ int dw_pcie_ep_init_complete(struct dw_pcie_ep *ep)
 	}
 
 	offset = dw_pcie_ep_find_ext_capability(pci, PCI_EXT_CAP_ID_REBAR);
+	ptm_cap_base = dw_pcie_ep_find_ext_capability(pci, PCI_EXT_CAP_ID_PTM);
 
 	dw_pcie_dbi_ro_wr_en(pci);
 
@@ -671,6 +672,22 @@ int dw_pcie_ep_init_complete(struct dw_pcie_ep *ep)
 			dw_pcie_writel_dbi(pci, offset + PCI_REBAR_CAP, 0x0);
 	}
 
+	/*
+	 * PTM responder capability can be disabled only after disabling
+	 * PTM root capability.
+	 */
+	if (ptm_cap_base) {
+		dw_pcie_dbi_ro_wr_en(pci);
+		reg = dw_pcie_readl_dbi(pci, ptm_cap_base + PCI_PTM_CAP);
+		reg &= ~PCI_PTM_CAP_ROOT;
+		dw_pcie_writel_dbi(pci, ptm_cap_base + PCI_PTM_CAP, reg);
+
+		reg = dw_pcie_readl_dbi(pci, ptm_cap_base + PCI_PTM_CAP);
+		reg &= ~(PCI_PTM_CAP_RES | PCI_PTM_GRANULARITY_MASK);
+		dw_pcie_writel_dbi(pci, ptm_cap_base + PCI_PTM_CAP, reg);
+		dw_pcie_dbi_ro_wr_dis(pci);
+	}
+
 	dw_pcie_setup(pci);
 	dw_pcie_dbi_ro_wr_dis(pci);