1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * 8237A DMA controller suspend functions. 4 * 5 * Written by Pierre Ossman, 2005. 6 */ 7 8 #include <linux/dmi.h> 9 #include <linux/init.h> 10 #include <linux/syscore_ops.h> 11 12 #include <asm/dma.h> 13 #include <asm/x86_init.h> 14 15 /* 16 * This module just handles suspend/resume issues with the 17 * 8237A DMA controller (used for ISA and LPC). 18 * Allocation is handled in kernel/dma.c and normal usage is 19 * in asm/dma.h. 20 */ 21 22 static void i8237A_resume(void) 23 { 24 unsigned long flags; 25 int i; 26 27 flags = claim_dma_lock(); 28 29 dma_outb(0, DMA1_RESET_REG); 30 dma_outb(0, DMA2_RESET_REG); 31 32 for (i = 0; i < 8; i++) { 33 set_dma_addr(i, 0x000000); 34 /* DMA count is a bit weird so this is not 0 */ 35 set_dma_count(i, 1); 36 } 37 38 /* Enable cascade DMA or channel 0-3 won't work */ 39 enable_dma(4); 40 41 release_dma_lock(flags); 42 } 43 44 static struct syscore_ops i8237_syscore_ops = { 45 .resume = i8237A_resume, 46 }; 47 48 static int __init i8237A_init_ops(void) 49 { 50 /* 51 * From SKL PCH onwards, the legacy DMA device is removed in which the 52 * I/O ports (81h-83h, 87h, 89h-8Bh, 8Fh) related to it are removed 53 * as well. All removed ports must return 0xff for a inb() request. 54 * 55 * Note: DMA_PAGE_2 (port 0x81) should not be checked for detecting 56 * the presence of DMA device since it may be used by BIOS to decode 57 * LPC traffic for POST codes. Original LPC only decodes one byte of 58 * port 0x80 but some BIOS may choose to enhance PCH LPC port 0x8x 59 * decoding. 60 */ 61 if (dma_inb(DMA_PAGE_0) == 0xFF) 62 return -ENODEV; 63 64 /* 65 * It is not required to load this driver as newer SoC may not 66 * support 8237 DMA or bus mastering from LPC. Platform firmware 67 * must announce the support for such legacy devices via 68 * ACPI_FADT_LEGACY_DEVICES field in FADT table. 69 */ 70 if (x86_pnpbios_disabled() && dmi_get_bios_year() >= 2017) 71 return -ENODEV; 72 73 register_syscore_ops(&i8237_syscore_ops); 74 return 0; 75 } 76 device_initcall(i8237A_init_ops); 77