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f79b1c573c
From Skylake onwards, the platform controller hub (Sunrisepoint PCH) does
not support legacy DMA operations to IO ports 81h-83h, 87h, 89h-8Bh, 8Fh.
Currently this driver registers as syscore ops and its resume function is
called on every resume from S3. On Skylake and Kabylake, this causes a
resume delay of around 100ms due to port IO operations, which is a problem.
This change allows to load the driver only when the platform bios
explicitly supports such devices or has a cut-off date earlier than 2017
due to the following reasons:
- The platforms released before year 2017 have support for the 8237.
(except Sunrisepoint PCH e.g. Skylake)
- Some of the BIOS that were released for platforms (Skylake, Kabylake)
during 2016-17 are buggy. These BIOS do not set/unset the
ACPI_FADT_LEGACY_DEVICES field in FADT table properly based on the
presence or absence of the DMA device.
Very recently, open source system firmware like coreboot started unsetting
ACPI_FADT_LEGACY_DEVICES field in FADT table if the 8237 DMA device is not
present on the PCH.
Please refer to chapter 21 of 6th Generation Intel® Core™ Processor
Platform Controller Hub Family: BIOS Specification.
Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: rjw@rjwysocki.net
Cc: hpa@zytor.com
Cc: Alan Cox <alan@linux.intel.com>
Link: https://lkml.kernel.org/r/1522336015-22994-1-git-send-email-anshuman.gupta@intel.com
81 lines
2.1 KiB
C
81 lines
2.1 KiB
C
/*
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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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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or (at
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* your option) any later version.
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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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