[PATCH v4 5/6] PCI: dwc: rcar-gen4: Handle PERST via reset subsystem

[Marek Vasut <marek.vasut+renesas@mailbox.org>]

Handle PERST via both GPIO and reset subsystem. On R-Car Gen4, the
PERST signal is operated as a GPIO, on R-Car Gen5 it might only be
accessible via SCMI reset via reset subsystem. Support both options.
This is a preparatory patch for R-Car Gen5 support.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
---
Cc: "Krzysztof Wilczyński" <kwilczynski@kernel.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Conor Dooley <conor+dt@kernel.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
Cc: Lorenzo Pieralisi <lpieralisi@kernel.org>
Cc: Manivannan Sadhasivam <mani@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-pci@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org
---
V2: - Use dev_err_probe() for perst in rcar_gen4_pcie_get_resources()
    - Use of_get_next_available_child() to obtain root port OF node
    - Switch to of_reset_control_get_optional_exclusive() to deal with
      R-Car Gen4, where the PERST is handled as GPIO instead of reset
    - Rename rcar_gen4_pcie_host_perst() to rcar_gen4_pcie_host_perst_assert()
      and use bool type for assert and deassert selection
    - Add missing reset_control_put() into rcar_gen4_pcie_probe() fail path
V3: - Handle controllers without root port DT node
    - Swap fail path order
V4: Rebase on next-20260904
---
 drivers/pci/controller/dwc/pcie-rcar-gen4.c | 44 +++++++++++++++++++--
 1 file changed, 40 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-rcar-gen4.c b/drivers/pci/controller/dwc/pcie-rcar-gen4.c
index c768a9c7b3b76..89472a4becc46 100644
--- a/drivers/pci/controller/dwc/pcie-rcar-gen4.c
+++ b/drivers/pci/controller/dwc/pcie-rcar-gen4.c
@@ -99,6 +99,7 @@ struct rcar_gen4_pcie {
 	void __iomem *base;
 	void __iomem *phy_base;
 	struct platform_device *pdev;
+	struct reset_control *perst;
 	const struct rcar_gen4_pcie_drvdata *drvdata;
 };
 #define to_rcar_gen4_pcie(_dw)	container_of(_dw, struct rcar_gen4_pcie, dw)
@@ -317,12 +318,27 @@ static void rcar_gen4_pcie_unprepare(struct rcar_gen4_pcie *rcar)
 
 static int rcar_gen4_pcie_get_resources(struct rcar_gen4_pcie *rcar)
 {
+	struct device *dev = rcar->dw.dev;
+	struct device_node *root_port;
+
 	rcar->phy_base = devm_platform_ioremap_resource_byname(rcar->pdev, "phy");
 	if (IS_ERR(rcar->phy_base))
 		return PTR_ERR(rcar->phy_base);
 
+	root_port = of_get_next_available_child(dev->of_node, NULL);
+	if (root_port) {
+		rcar->perst = of_reset_control_get_optional_exclusive(root_port, "perst");
+		of_node_put(root_port);
+		if (IS_ERR(rcar->perst))
+			return dev_err_probe(dev, PTR_ERR(rcar->perst), "Failed to get PERST#\n");
+	} else {
+		rcar->perst = NULL;
+	}
+
 	/* Renesas-specific registers */
 	rcar->base = devm_platform_ioremap_resource_byname(rcar->pdev, "app");
+	if (IS_ERR(rcar->base))
+		reset_control_put(rcar->perst);
 
 	return PTR_ERR_OR_ZERO(rcar->base);
 }
@@ -494,6 +510,22 @@ static int rcar_gen4_pcie_enable_device(struct pci_host_bridge *bridge,
 	return 0;
 }
 
+static void rcar_gen4_pcie_host_perst_assert(struct dw_pcie_rp *pp, bool assert)
+{
+	struct dw_pcie *dw = to_dw_pcie_from_pp(pp);
+	struct rcar_gen4_pcie *rcar = to_rcar_gen4_pcie(dw);
+
+	gpiod_set_value_cansleep(dw->pe_rst, assert);
+
+	if (!rcar->perst)
+		return;
+
+	if (assert)
+		reset_control_assert(rcar->perst);
+	else
+		reset_control_deassert(rcar->perst);
+}
+
 /* Host mode */
 static int rcar_gen4_pcie_host_init(struct dw_pcie_rp *pp)
 {
@@ -504,7 +536,7 @@ static int rcar_gen4_pcie_host_init(struct dw_pcie_rp *pp)
 	if (pp->bridge)
 		pp->bridge->enable_device = rcar_gen4_pcie_enable_device;
 
-	gpiod_set_value_cansleep(dw->pe_rst, 1);
+	rcar_gen4_pcie_host_perst_assert(pp, true);
 
 	ret = rcar->drvdata->init(rcar);
 	if (ret)
@@ -525,7 +557,7 @@ static int rcar_gen4_pcie_host_init(struct dw_pcie_rp *pp)
 
 	msleep(PCIE_T_PVPERL_MS);	/* pe_rst requires 100msec delay */
 
-	gpiod_set_value_cansleep(dw->pe_rst, 0);
+	rcar_gen4_pcie_host_perst_assert(pp, false);
 
 	return 0;
 
@@ -539,7 +571,7 @@ static void rcar_gen4_pcie_host_deinit(struct dw_pcie_rp *pp)
 	struct dw_pcie *dw = to_dw_pcie_from_pp(pp);
 	struct rcar_gen4_pcie *rcar = to_rcar_gen4_pcie(dw);
 
-	gpiod_set_value_cansleep(dw->pe_rst, 1);
+	rcar_gen4_pcie_host_perst_assert(pp, true);
 	rcar->drvdata->deinit(rcar);
 }
 
@@ -713,7 +745,7 @@ static int rcar_gen4_pcie_probe(struct platform_device *pdev)
 
 	err = rcar_gen4_pcie_prepare(rcar);
 	if (err)
-		return err;
+		goto err_prepare;
 
 	err = rcar_gen4_add_dw_pcie(rcar);
 	if (err)
@@ -724,6 +756,9 @@ static int rcar_gen4_pcie_probe(struct platform_device *pdev)
 err_unprepare:
 	rcar_gen4_pcie_unprepare(rcar);
 
+err_prepare:
+	reset_control_put(rcar->perst);
+
 	return err;
 }
 
@@ -747,6 +782,7 @@ static void rcar_gen4_pcie_remove(struct platform_device *pdev)
 
 	rcar_gen4_remove_dw_pcie(rcar);
 	rcar_gen4_pcie_unprepare(rcar);
+	reset_control_put(rcar->perst);
 }
 
 static int r8a779f0_pcie_ltssm_control(struct rcar_gen4_pcie *rcar, bool enable)
-- 
2.53.0