[v1,2/8] ACPI: ASPT: Add helper to parse table

diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
index 0002eecbf870..9621c90e0221 100644
--- a/drivers/acpi/Makefile
+++ b/drivers/acpi/Makefile
@@ -57,6 +57,7 @@  acpi-y				+= evged.o
 acpi-y				+= sysfs.o
 acpi-y				+= property.o
 acpi-$(CONFIG_X86)		+= acpi_cmos_rtc.o
+acpi-$(CONFIG_X86)		+= aspt.o
 acpi-$(CONFIG_X86)		+= x86/apple.o
 acpi-$(CONFIG_X86)		+= x86/utils.o
 acpi-$(CONFIG_X86)		+= x86/s2idle.o
diff --git a/drivers/acpi/aspt.c b/drivers/acpi/aspt.c
new file mode 100644
index 000000000000..cf629db35036
--- /dev/null
+++ b/drivers/acpi/aspt.c
@@ -0,0 +1,104 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+#define pr_fmt(fmt) "ACPI: ASPT: " fmt
+#include <linux/acpi.h>
+#include <linux/kernel.h>
+#include <linux/platform_data/psp.h>
+
+static int __init psp_validate_regs(const struct acpi_aspt_global_regs *gregs,
+	const struct acpi_aspt_sev_mbox_regs *sevregs,
+	const struct acpi_aspt_acpi_mbox_regs *acpiregs)
+{
+	u64 pfn;
+	int idx;
+	u64 regs[] = {
+		gregs->feature_reg_addr,
+		gregs->irq_en_reg_addr,
+		gregs->irq_st_reg_addr,
+		sevregs->cmd_resp_reg_addr,
+		sevregs->cmd_buf_lo_reg_addr,
+		sevregs->cmd_buf_hi_reg_addr,
+		acpiregs->cmd_resp_reg_addr
+	};
+	pfn = regs[0] >> PAGE_SHIFT;
+	for (idx = 1; idx < ARRAY_SIZE(regs); idx++) {
+		if (regs[idx] >> PAGE_SHIFT != pfn)
+			return -EINVAL;
+	}
+	return 0;
+}
+
+/**
+ * acpi_parse_aspt - Parse ASPT table and return contained information
+ * @res: will be filled with the address and size of the ASP register window
+ * @pdata: will be filled with the register offsets parsed from the ASPT table
+ */
+int __init acpi_parse_aspt(struct resource *res, struct psp_platform_data *pdata)
+{
+	struct acpi_aspt_acpi_mbox_regs acpiregs = {};
+	struct acpi_aspt_sev_mbox_regs sevregs = {};
+	struct acpi_aspt_global_regs gregs = {};
+	struct acpi_aspt_header *entry, *end;
+	struct acpi_table_aspt *aspt;
+	unsigned long base;
+	acpi_status status;
+	int err = 0;
+
+	status = acpi_get_table(ACPI_SIG_ASPT, 0, (struct acpi_table_header **)&aspt);
+	if (ACPI_FAILURE(status))
+		return -ENODEV;
+	if (aspt->header.revision != ASPT_REVISION_ID) {
+		pr_err("unsupported table revision: %d\n", (int)aspt->header.revision);
+		err = -ENODEV;
+		goto exit;
+	}
+	entry = (struct acpi_aspt_header *)(aspt + 1);
+	end = (struct acpi_aspt_header *)((void *)aspt + aspt->header.length);
+	while (entry < end) {
+		if (((void *)entry + entry->length) > (void *)end) {
+			pr_err("error during parsing\n");
+			err = -EINVAL;
+			goto exit;
+		}
+		switch (entry->type) {
+		case ACPI_ASPT_TYPE_GLOBAL_REGS:
+			memcpy(&gregs, entry, entry->length);
+			break;
+		case ACPI_ASPT_TYPE_SEV_MBOX_REGS:
+			memcpy(&sevregs, entry, entry->length);
+			break;
+		case ACPI_ASPT_TYPE_ACPI_MBOX_REGS:
+			memcpy(&acpiregs, entry, entry->length);
+			break;
+		}
+		entry = (struct acpi_aspt_header *)((void *)entry + entry->length);
+	}
+	if (!gregs.header.length || !sevregs.header.length || !acpiregs.header.length) {
+		pr_err("missing ASPT table entry: %u %u %u\n", gregs.header.length,
+			sevregs.header.length,
+			acpiregs.header.length);
+		err = -EINVAL;
+		goto exit;
+	}
+	/* All registers are expected to be within the same page */
+	err = psp_validate_regs(&gregs, &sevregs, &acpiregs);
+	if (err) {
+		pr_err("ASPT registers span multiple pages\n");
+		goto exit;
+	}
+
+	base = ALIGN_DOWN(gregs.feature_reg_addr, PAGE_SIZE);
+	*res = (struct resource)DEFINE_RES_MEM(base, PAGE_SIZE);
+
+	pdata->sev_cmd_resp_reg = sevregs.cmd_resp_reg_addr & ~PAGE_MASK;
+	pdata->sev_cmd_buf_lo_reg = sevregs.cmd_buf_lo_reg_addr & ~PAGE_MASK;
+	pdata->sev_cmd_buf_hi_reg = sevregs.cmd_buf_hi_reg_addr & ~PAGE_MASK;
+	pdata->feature_reg = gregs.feature_reg_addr & ~PAGE_MASK;
+	pdata->irq_en_reg = gregs.irq_en_reg_addr & ~PAGE_MASK;
+	pdata->irq_st_reg = gregs.irq_st_reg_addr & ~PAGE_MASK;
+	pdata->mbox_irq_id = sevregs.mbox_irq_id;
+	pdata->acpi_cmd_resp_reg = acpiregs.cmd_resp_reg_addr & ~PAGE_MASK;
+
+exit:
+	acpi_put_table((struct acpi_table_header *)aspt);
+	return err;
+}
diff --git a/include/linux/platform_data/psp.h b/include/linux/platform_data/psp.h
new file mode 100644
index 000000000000..b761f72168d6
--- /dev/null
+++ b/include/linux/platform_data/psp.h
@@ -0,0 +1,32 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * psp.h - PSP register offsets parsed from ASPT ACPI table
+ */
+
+#ifndef __LINUX_PSP_H
+#define __LINUX_PSP_H
+
+#include <linux/types.h>
+#include <linux/ioport.h>
+
+struct psp_platform_data {
+	int sev_cmd_resp_reg;
+	int sev_cmd_buf_lo_reg;
+	int sev_cmd_buf_hi_reg;
+	int feature_reg;
+	int irq_en_reg;
+	int irq_st_reg;
+	int mbox_irq_id;
+	int acpi_cmd_resp_reg;
+};
+
+#if IS_ENABLED(CONFIG_ACPI)
+int acpi_parse_aspt(struct resource *res, struct psp_platform_data *pdata);
+#else
+static inline acpi_parse_aspt(struct resource *res, struct psp_platform_data *pdata)
+{
+	return -ENODEV;
+}
+#endif
+
+#endif /* __LINUX_PSP_H */