PCI: brcmstb: Use bridge reset if available

The 7712 SoC has a bridge reset which can be described in the device
tree.

Use it if present.  Otherwise, continue to use the legacy method to
reset the bridge.

Link: https://lore.kernel.org/linux-pci/20240815225731.40276-6-james.quinlan@broadcom.com
Signed-off-by: Jim Quinlan <james.quinlan@broadcom.com>
[kwilczynski: commit log, refactored function brcm_pcie_bridge_sw_init_set_generic()]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Stanimir Varbanov <svarbanov@suse.de>

Author: jamesequinlan

drivers/pci/controller/pcie-brcmstb.c

@@ -265,6 +265,7 @@ struct brcm_pcie {
 	enum pcie_type		type;
 	struct reset_control	*rescal;
 	struct reset_control	*perst_reset;
+	struct reset_control	*bridge_reset;
 	int			num_memc;
 	u64			memc_size[PCIE_BRCM_MAX_MEMC];
 	u32			hw_rev;
@@ -732,9 +733,18 @@ static void __iomem *brcm7425_pcie_map_bus(struct pci_bus *bus,
 
 static void brcm_pcie_bridge_sw_init_set_generic(struct brcm_pcie *pcie, u32 val)
 {
-	u32 tmp, mask =  RGR1_SW_INIT_1_INIT_GENERIC_MASK;
+	u32 tmp, mask = RGR1_SW_INIT_1_INIT_GENERIC_MASK;
 	u32 shift = RGR1_SW_INIT_1_INIT_GENERIC_SHIFT;
 
+	if (pcie->bridge_reset) {
+		if (val)
+			reset_control_assert(pcie->bridge_reset);
+		else
+			reset_control_deassert(pcie->bridge_reset);
+
+		return;
+	}
+
 	tmp = readl(pcie->base + PCIE_RGR1_SW_INIT_1(pcie));
 	tmp = (tmp & ~mask) | ((val << shift) & mask);
 	writel(tmp, pcie->base + PCIE_RGR1_SW_INIT_1(pcie));
@@ -1621,10 +1631,16 @@ static int brcm_pcie_probe(struct platform_device *pdev)
 	if (IS_ERR(pcie->perst_reset))
 		return PTR_ERR(pcie->perst_reset);
 
+	pcie->bridge_reset = devm_reset_control_get_optional_exclusive(&pdev->dev, "bridge");
+	if (IS_ERR(pcie->bridge_reset))
+		return PTR_ERR(pcie->bridge_reset);
+
 	ret = clk_prepare_enable(pcie->clk);
 	if (ret)
 		return dev_err_probe(&pdev->dev, ret, "could not enable clock\n");
 
+	pcie->bridge_sw_init_set(pcie, 0);
+
 	ret = reset_control_reset(pcie->rescal);
 	if (ret) {
 		clk_disable_unprepare(pcie->clk);