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