PCI: dwc: Implement .assert_perst() for dwc glue drivers

Add .assert_perst() hook for dwc glue drivers to register with
assert_perst() of pci ops, allowing for better control over the link
initialization and shutdown process.

Implement assert_perst() function op for dwc drivers.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
[bhelgaas: squash dwc host support]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://patch.msgid.link/20251101-tc9563-v9-3-de3429f7787a@oss.qualcomm.com
Link: https://patch.msgid.link/20251101-tc9563-v9-4-de3429f7787a@oss.qualcomm.com

Author: krishnachaitanya-linux

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

@@ -842,10 +842,19 @@ void __iomem *dw_pcie_own_conf_map_bus(struct pci_bus *bus, unsigned int devfn,
 }
 EXPORT_SYMBOL_GPL(dw_pcie_own_conf_map_bus);
 
+static int dw_pcie_op_assert_perst(struct pci_bus *bus, bool assert)
+{
+	struct dw_pcie_rp *pp = bus->sysdata;
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+
+	return dw_pcie_assert_perst(pci, assert);
+}
+
 static struct pci_ops dw_pcie_ops = {
 	.map_bus = dw_pcie_own_conf_map_bus,
 	.read = pci_generic_config_read,
 	.write = pci_generic_config_write,
+	.assert_perst = dw_pcie_op_assert_perst,
 };
 
 static int dw_pcie_iatu_setup(struct dw_pcie_rp *pp)

drivers/pci/controller/dwc/pcie-designware.h

@@ -485,6 +485,7 @@ struct dw_pcie_ops {
 	enum dw_pcie_ltssm (*get_ltssm)(struct dw_pcie *pcie);
 	int	(*start_link)(struct dw_pcie *pcie);
 	void	(*stop_link)(struct dw_pcie *pcie);
+	int	(*assert_perst)(struct dw_pcie *pcie, bool assert);
 };
 
 struct debugfs_info {
@@ -787,6 +788,14 @@ static inline void dw_pcie_stop_link(struct dw_pcie *pci)
 		pci->ops->stop_link(pci);
 }
 
+static inline int dw_pcie_assert_perst(struct dw_pcie *pci, bool assert)
+{
+	if (pci->ops && pci->ops->assert_perst)
+		return pci->ops->assert_perst(pci, assert);
+
+	return 0;
+}
+
 static inline enum dw_pcie_ltssm dw_pcie_get_ltssm(struct dw_pcie *pci)
 {
 	u32 val;