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-rw-r--r--arch/x86/kernel/i8237.c76
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
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+++ b/arch/x86/kernel/i8237.c
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+// 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);