[PATCH for 6.6] LoongArch: Add PIO for early access before ACPI PCI root register

[PATCH for 6.6] LoongArch: Add PIO for early access before ACPI PCI root register

[Huacai Chen]

commit 6061e65f95713b01f4313cda6637dfe3aa5412b4 upstream.

For ACPI system we suppose the ISA/LPC PIO range is registered together
with PCI root bridge. But the fact is there may be some early access to
the ISA/LPC PIO range before ACPI PCI root register (most of them are
due to abnormal BIOS). Unconditionally register the ISA/LPC PIO range
usually causes ACPI PCI root register fail because of the address range
confliction. So we add a pair of helpers: acpi_add_early_pio() to add
PIO for early access, and acpi_remove_early_pio() to remove PIO before
PCI root register. Since acpi_remove_early_pio() may be called multiple
times, we add an acpi_pio flag to ensure PIO be removed only once.

Cc: <stable@vger.kernel.org>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 arch/loongarch/include/asm/acpi.h |  2 ++
 arch/loongarch/kernel/acpi.c      | 28 ++++++++++++++++++++++++++++
 arch/loongarch/kernel/setup.c     |  2 ++
 arch/loongarch/pci/acpi.c         |  2 ++
 4 files changed, 34 insertions(+)

diff --git a/arch/loongarch/include/asm/acpi.h b/arch/loongarch/include/asm/acpi.h
index 7376840fa9f7..32999f281d5b 100644
--- a/arch/loongarch/include/asm/acpi.h
+++ b/arch/loongarch/include/asm/acpi.h
@@ -38,6 +38,8 @@ static inline bool acpi_has_cpu_in_madt(void)
 extern struct list_head acpi_wakeup_device_list;
 extern struct acpi_madt_core_pic acpi_core_pic[MAX_CORE_PIC];
 
+extern void acpi_add_early_pio(void);
+extern void acpi_remove_early_pio(void);
 extern int __init parse_acpi_topology(void);
 
 static inline u32 get_acpi_id_for_cpu(unsigned int cpu)
diff --git a/arch/loongarch/kernel/acpi.c b/arch/loongarch/kernel/acpi.c
index fba4bb93e1bd..ccd5d42f5b88 100644
--- a/arch/loongarch/kernel/acpi.c
+++ b/arch/loongarch/kernel/acpi.c
@@ -15,6 +15,7 @@
 #include <linux/memblock.h>
 #include <linux/of_fdt.h>
 #include <linux/serial_core.h>
+#include <linux/vmalloc.h>
 #include <asm/io.h>
 #include <asm/numa.h>
 #include <asm/loongson.h>
@@ -58,6 +59,33 @@ void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)
 		return ioremap_cache(phys, size);
 }
 
+#define PIO_BASE (unsigned long)PCI_IOBASE
+#define PIO_SIZE ALIGN(ISA_IOSIZE, PAGE_SIZE)
+
+static bool acpi_pio;
+
+/* Add PIO for early access */
+void acpi_add_early_pio(void)
+{
+	if (!acpi_disabled) {
+		acpi_pio = true;
+		ioremap_page_range(PIO_BASE, PIO_BASE + PIO_SIZE,
+				LOONGSON_LIO_BASE, pgprot_device(PAGE_KERNEL));
+	}
+}
+
+/* Remove PIO for PCI register */
+void acpi_remove_early_pio(void)
+{
+	if (!acpi_pio)
+		return;
+
+	if (!acpi_disabled) {
+		acpi_pio = false;
+		vunmap_range(PIO_BASE, PIO_BASE + PIO_SIZE);
+	}
+}
+
 #ifdef CONFIG_SMP
 static int set_processor_mask(u32 id, u32 pass)
 {
diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index a16665c0c1ae..5e441ed23c12 100644
--- a/arch/loongarch/kernel/setup.c
+++ b/arch/loongarch/kernel/setup.c
@@ -538,6 +538,8 @@ static __init int arch_reserve_pio_range(void)
 {
 	struct device_node *np;
 
+	acpi_add_early_pio();
+
 	for_each_node_by_name(np, "isa") {
 		struct of_range range;
 		struct of_range_parser parser;
diff --git a/arch/loongarch/pci/acpi.c b/arch/loongarch/pci/acpi.c
index a6d869e103c1..1a28fe847d47 100644
--- a/arch/loongarch/pci/acpi.c
+++ b/arch/loongarch/pci/acpi.c
@@ -65,6 +65,8 @@ static int acpi_prepare_root_resources(struct acpi_pci_root_info *ci)
 	struct resource_entry *entry, *tmp;
 	struct acpi_device *device = ci->bridge;
 
+	acpi_remove_early_pio();
+
 	status = acpi_pci_probe_root_resources(ci);
 	if (status > 0) {
 		acpi_evaluate_integer(device->handle, "PCIH", NULL, &pci_h);
-- 
2.52.0

Re: [PATCH for 6.6] LoongArch: Add PIO for early access before ACPI PCI root register

[Sasha Levin]

On Thu, Jul 10, 2026 at 08:26:13PM +0800, Huacai Chen wrote:
> commit 6061e65f95713b01f4313cda6637dfe3aa5412b4 upstream.
>
> For ACPI system we suppose the ISA/LPC PIO range is registered together
> with PCI root bridge. But the fact is there may be some early access to
> the ISA/LPC PIO range before ACPI PCI root register (most of them are
> due to abnormal BIOS).

Queued for 6.6, thanks. I fixed up one context line in
arch/loongarch/kernel/acpi.c that didn't match the 6.6.y tree.

-- 
Thanks,
Sasha