1 /* 2 * 8237A DMA controller suspend functions. 3 * 4 * Written by Pierre Ossman, 2005. 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License as published by 8 * the Free Software Foundation; either version 2 of the License, or (at 9 * your option) any later version. 10 */ 11 12 #include <linux/dmi.h> 13 #include <linux/init.h> 14 #include <linux/syscore_ops.h> 15 16 #include <asm/dma.h> 17 #include <asm/x86_init.h> 18 19 /* 20 * This module just handles suspend/resume issues with the 21 * 8237A DMA controller (used for ISA and LPC). 22 * Allocation is handled in kernel/dma.c and normal usage is 23 * in asm/dma.h. 24 */ 25 26 static void i8237A_resume(void) 27 { 28 unsigned long flags; 29 int i; 30 31 flags = claim_dma_lock(); 32 33 dma_outb(0, DMA1_RESET_REG); 34 dma_outb(0, DMA2_RESET_REG); 35 36 for (i = 0; i < 8; i++) { 37 set_dma_addr(i, 0x000000); 38 /* DMA count is a bit weird so this is not 0 */ 39 set_dma_count(i, 1); 40 } 41 42 /* Enable cascade DMA or channel 0-3 won't work */ 43 enable_dma(4); 44 45 release_dma_lock(flags); 46 } 47 48 static struct syscore_ops i8237_syscore_ops = { 49 .resume = i8237A_resume, 50 }; 51 52 static int __init i8237A_init_ops(void) 53 { 54 /* 55 * From SKL PCH onwards, the legacy DMA device is removed in which the 56 * I/O ports (81h-83h, 87h, 89h-8Bh, 8Fh) related to it are removed 57 * as well. All removed ports must return 0xff for a inb() request. 58 * 59 * Note: DMA_PAGE_2 (port 0x81) should not be checked for detecting 60 * the presence of DMA device since it may be used by BIOS to decode 61 * LPC traffic for POST codes. Original LPC only decodes one byte of 62 * port 0x80 but some BIOS may choose to enhance PCH LPC port 0x8x 63 * decoding. 64 */ 65 if (dma_inb(DMA_PAGE_0) == 0xFF) 66 return -ENODEV; 67 68 /* 69 * It is not required to load this driver as newer SoC may not 70 * support 8237 DMA or bus mastering from LPC. Platform firmware 71 * must announce the support for such legacy devices via 72 * ACPI_FADT_LEGACY_DEVICES field in FADT table. 73 */ 74 if (x86_pnpbios_disabled() && dmi_get_bios_year() >= 2017) 75 return -ENODEV; 76 77 register_syscore_ops(&i8237_syscore_ops); 78 return 0; 79 } 80 device_initcall(i8237A_init_ops); 81