1 files changed, 76 insertions, 0 deletions
diff --git a/arch/x86/kernel/i8237.c b/arch/x86/kernel/i8237.c
new file mode 100644
index 000000000..2cd124ad9
--- /dev/null
+++ b/arch/x86/kernel/i8237.c
@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * 8237A DMA controller suspend functions.
+ *
+ * Written by Pierre Ossman, 2005.
+ */
+
+#include <linux/dmi.h>
+#include <linux/init.h>
+#include <linux/syscore_ops.h>
+
+#include <asm/dma.h>
+#include <asm/x86_init.h>
+
+/*
+ * This module just handles suspend/resume issues with the
+ * 8237A DMA controller (used for ISA and LPC).
+ * Allocation is handled in kernel/dma.c and normal usage is
+ * in asm/dma.h.
+ */
+
+static void i8237A_resume(void)
+{
+	unsigned long flags;
+	int i;
+
+	flags = claim_dma_lock();
+
+	dma_outb(0, DMA1_RESET_REG);
+	dma_outb(0, DMA2_RESET_REG);
+
+	for (i = 0; i < 8; i++) {
+		set_dma_addr(i, 0x000000);
+		/* DMA count is a bit weird so this is not 0 */
+		set_dma_count(i, 1);
+	}
+
+	/* Enable cascade DMA or channel 0-3 won't work */
+	enable_dma(4);
+
+	release_dma_lock(flags);
+}
+
+static struct syscore_ops i8237_syscore_ops = {
+	.resume		= i8237A_resume,
+};
+
+static int __init i8237A_init_ops(void)
+{
+	/*
+	 * From SKL PCH onwards, the legacy DMA device is removed in which the
+	 * I/O ports (81h-83h, 87h, 89h-8Bh, 8Fh) related to it are removed
+	 * as well. All removed ports must return 0xff for a inb() request.
+	 *
+	 * Note: DMA_PAGE_2 (port 0x81) should not be checked for detecting
+	 * the presence of DMA device since it may be used by BIOS to decode
+	 * LPC traffic for POST codes. Original LPC only decodes one byte of
+	 * port 0x80 but some BIOS may choose to enhance PCH LPC port 0x8x
+	 * decoding.
+	 */
+	if (dma_inb(DMA_PAGE_0) == 0xFF)
+		return -ENODEV;
+
+	/*
+	 * It is not required to load this driver as newer SoC may not
+	 * support 8237 DMA or bus mastering from LPC. Platform firmware
+	 * must announce the support for such legacy devices via
+	 * ACPI_FADT_LEGACY_DEVICES field in FADT table.
+	 */
+	if (x86_pnpbios_disabled() && dmi_get_bios_year() >= 2017)
+		return -ENODEV;
+
+	register_syscore_ops(&i8237_syscore_ops);
+	return 0;
+}
+device_initcall(i8237A_init_ops);