linux-kernel - [PATCH 1/2] PCI: rzg3s-host: Use pci_generic_config

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Message-ID: <20251205112443.1408518-2-claudiu.beznea.uj@bp.renesas.com>
Date: Fri,  5 Dec 2025 13:24:42 +0200
From: Claudiu <claudiu.beznea@...on.dev>
To: bhelgaas@...gle.com,
	lpieralisi@...nel.org,
	kwilczynski@...nel.org,
	mani@...nel.org,
	robh@...nel.org
Cc: claudiu.beznea@...on.dev,
	linux-pci@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>,
	Bjorn Helgaas <helgaas@...nel.org>
Subject: [PATCH 1/2] PCI: rzg3s-host: Use pci_generic_config_write() for the root bus

From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>

The Renesas RZ/G3S host controller allows writing to read-only PCIe
configuration registers when the RZG3S_PCI_PERM_CFG_HWINIT_EN bit is set in
the RZG3S_PCI_PERM register. However, callers of struct pci_ops::write
expect the semantics defined by the PCIe specification, meaning that writes
to read-only registers must not be allowed.

The previous custom struct pci_ops::write implementation for the root bus
temporarily enabled write access before calling pci_generic_config_write().
This breaks the expected semantics.

Remove the custom implementation and simply use pci_generic_config_write().

Along with this change, the updates of the PCI_PRIMARY_BUS,
PCI_SECONDARY_BUS, and PCI_SUBORDINATE_BUS registers were moved so that
they no longer depends on the RZG3S_PCI_PERM_CFG_HWINIT_EN bit in the
RZG3S_PCI_PERM_CFG register, since these registers are R/W.

Suggested-by: Bjorn Helgaas <helgaas@...nel.org>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
---
 drivers/pci/controller/pcie-rzg3s-host.c | 27 ++++--------------------
 1 file changed, 4 insertions(+), 23 deletions(-)

diff --git a/drivers/pci/controller/pcie-rzg3s-host.c b/drivers/pci/controller/pcie-rzg3s-host.c
index 667e6d629474..547cbe676a25 100644
--- a/drivers/pci/controller/pcie-rzg3s-host.c
+++ b/drivers/pci/controller/pcie-rzg3s-host.c
@@ -439,28 +439,9 @@ static void __iomem *rzg3s_pcie_root_map_bus(struct pci_bus *bus,
 	return host->pcie + where;
 }
 
-/* Serialized by 'pci_lock' */
-static int rzg3s_pcie_root_write(struct pci_bus *bus, unsigned int devfn,
-				 int where, int size, u32 val)
-{
-	struct rzg3s_pcie_host *host = bus->sysdata;
-	int ret;
-
-	/* Enable access control to the CFGU */
-	writel_relaxed(RZG3S_PCI_PERM_CFG_HWINIT_EN,
-		       host->axi + RZG3S_PCI_PERM);
-
-	ret = pci_generic_config_write(bus, devfn, where, size, val);
-
-	/* Disable access control to the CFGU */
-	writel_relaxed(0, host->axi + RZG3S_PCI_PERM);
-
-	return ret;
-}
-
 static struct pci_ops rzg3s_pcie_root_ops = {
 	.read		= pci_generic_config_read,
-	.write		= rzg3s_pcie_root_write,
+	.write		= pci_generic_config_write,
 	.map_bus	= rzg3s_pcie_root_map_bus,
 };
 
@@ -1065,14 +1046,14 @@ static int rzg3s_pcie_config_init(struct rzg3s_pcie_host *host)
 	writel_relaxed(0xffffffff, host->pcie + RZG3S_PCI_CFG_BARMSK00L);
 	writel_relaxed(0xffffffff, host->pcie + RZG3S_PCI_CFG_BARMSK00U);
 
+	/* Disable access control to the CFGU */
+	writel_relaxed(0, host->axi + RZG3S_PCI_PERM);
+
 	/* Update bus info */
 	writeb_relaxed(primary_bus, host->pcie + PCI_PRIMARY_BUS);
 	writeb_relaxed(secondary_bus, host->pcie + PCI_SECONDARY_BUS);
 	writeb_relaxed(subordinate_bus, host->pcie + PCI_SUBORDINATE_BUS);
 
-	/* Disable access control to the CFGU */
-	writel_relaxed(0, host->axi + RZG3S_PCI_PERM);
-
 	return 0;
 }
 
-- 
2.43.0