[PATCH 2/2] ACPI: LoongArch: Add checksum support with IOVT table

[Bibo Mao]

Checksum information is put in acpi_table_header, here add
checksum support with IOVT table.

Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx>
---
 drivers/acpi/loongarch/iovt.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/acpi/loongarch/iovt.c b/drivers/acpi/loongarch/iovt.c
index 6c5bcb4df7d8..c9830ba46729 100644
--- a/drivers/acpi/loongarch/iovt.c
+++ b/drivers/acpi/loongarch/iovt.c
@@ -20,6 +20,7 @@ struct iovt_fwnode {
 
 static LIST_HEAD(iovt_fwnode_list);
 static DEFINE_SPINLOCK(iovt_fwnode_lock);
+static bool checksum_valid;
 
 #ifdef CONFIG_PCI
 static void __init iovt_enable_acs(struct acpi_iovt_iommu *iommu)
@@ -168,6 +169,17 @@ static void __init iovt_init_devices(struct acpi_table_header *header)
 	}
 }
 
+/* Come from acpi_ut_checksum */
+static unsigned char acpi_iovt_checksum(unsigned char *buffer, unsigned int len)
+{
+	unsigned char sum = 0, *end = buffer + len;
+
+	while (buffer < end)
+		sum += *buffer++;
+
+	return sum;
+}
+
 void __init acpi_iovt_init(void)
 {
 	int i;
@@ -184,6 +196,13 @@ void __init acpi_iovt_init(void)
 		return;
 	}
 
+	if (acpi_iovt_checksum((unsigned char *)hdr, hdr->length)) {
+		pr_err("IOVT invalid checksum\n");
+		acpi_put_table(hdr);
+		return;
+	}
+
+	checksum_valid = true;
 	iovt = (struct acpi_table_iovt *)hdr;
 	iommu = ACPI_ADD_PTR(struct acpi_iovt_iommu, iovt, iovt->iommu_offset);
 	for (i = 0; i < iovt->iommu_count; i++) {
@@ -199,6 +218,9 @@ void __init acpi_iovt_late_init(void)
 	acpi_status status;
 	struct acpi_table_header *hdr;
 
+	if (!checksum_valid)
+		return;
+
 	status = acpi_get_table(ACPI_SIG_IOVT, 0, &hdr);
 	if (ACPI_FAILURE(status)) {
 		if (status != AE_NOT_FOUND)
-- 
2.39.3