linux-kernel - [PATCH v2 04/11] PCI: pci-bridge-emul: Add support for new flag PCI_BRIDGE_EMUL_NO_IO

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Date:   Tue,  4 Jan 2022 16:35:22 +0100
From:   Pali Rohár <pali@...nel.org>
To:     Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Marek Behún <kabel@...nel.org>
Cc:     linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 04/11] PCI: pci-bridge-emul: Add support for new flag PCI_BRIDGE_EMUL_NO_IO_FORWARD

Like PCI_BRIDGE_EMUL_NO_PREFMEM_FORWARD, this new flag specifies that
emulated PCI bridge does not support forwarding of IO requests in given
range between primary and secondary buses. This flag should be used as
argument for pci_bridge_emul_init() for hardware setup without IO support.

Setting this flag cause that IO base and limit registers are read-only.

Signed-off-by: Pali Rohár <pali@...nel.org>

---
Changes in v2:
* Add comment into code.
---
 drivers/pci/pci-bridge-emul.c | 9 +++++++++
 drivers/pci/pci-bridge-emul.h | 6 ++++++
 2 files changed, 15 insertions(+)

diff --git a/drivers/pci/pci-bridge-emul.c b/drivers/pci/pci-bridge-emul.c
index 432b1bec2e22..033bbeb99176 100644
--- a/drivers/pci/pci-bridge-emul.c
+++ b/drivers/pci/pci-bridge-emul.c
@@ -378,6 +378,15 @@ int pci_bridge_emul_init(struct pci_bridge_emul *bridge,
 		bridge->pci_regs_behavior[PCI_PREF_MEMORY_BASE / 4].rw = 0;
 	}
 
+	if (flags & PCI_BRIDGE_EMUL_NO_IO_FORWARD) {
+		bridge->pci_regs_behavior[PCI_COMMAND / 4].ro |= PCI_COMMAND_IO;
+		bridge->pci_regs_behavior[PCI_COMMAND / 4].rw &= ~PCI_COMMAND_IO;
+		bridge->pci_regs_behavior[PCI_IO_BASE / 4].ro |= GENMASK(15, 0);
+		bridge->pci_regs_behavior[PCI_IO_BASE / 4].rw &= ~GENMASK(15, 0);
+		bridge->pci_regs_behavior[PCI_IO_BASE_UPPER16 / 4].ro = ~0;
+		bridge->pci_regs_behavior[PCI_IO_BASE_UPPER16 / 4].rw = 0;
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(pci_bridge_emul_init);
diff --git a/drivers/pci/pci-bridge-emul.h b/drivers/pci/pci-bridge-emul.h
index 087b5fa01bcf..4953274cac18 100644
--- a/drivers/pci/pci-bridge-emul.h
+++ b/drivers/pci/pci-bridge-emul.h
@@ -125,6 +125,12 @@ enum {
 	 * requests between primary and secondary buses.
 	 */
 	PCI_BRIDGE_EMUL_NO_PREFMEM_FORWARD = BIT(0),
+
+	/*
+	 * PCI bridge does not support forwarding of IO requests between
+	 * primary and secondary buses.
+	 */
+	PCI_BRIDGE_EMUL_NO_IO_FORWARD = BIT(1),
 };
 
 int pci_bridge_emul_init(struct pci_bridge_emul *bridge,
-- 
2.20.1