linux/arch/x86/kernel/platform-quirks.c
Rajneesh Bhardwaj f79b1c573c x86/i8237: Register device based on FADT legacy boot flag
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
2018-04-27 16:44:29 +02:00

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1.1 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/init.h>
#include <asm/setup.h>
#include <asm/bios_ebda.h>
void __init x86_early_init_platform_quirks(void)
{
x86_platform.legacy.i8042 = X86_LEGACY_I8042_EXPECTED_PRESENT;
x86_platform.legacy.rtc = 1;
x86_platform.legacy.warm_reset = 1;
x86_platform.legacy.reserve_bios_regions = 0;
x86_platform.legacy.devices.pnpbios = 1;
switch (boot_params.hdr.hardware_subarch) {
case X86_SUBARCH_PC:
x86_platform.legacy.reserve_bios_regions = 1;
break;
case X86_SUBARCH_XEN:
x86_platform.legacy.devices.pnpbios = 0;
x86_platform.legacy.rtc = 0;
break;
case X86_SUBARCH_INTEL_MID:
case X86_SUBARCH_CE4100:
x86_platform.legacy.devices.pnpbios = 0;
x86_platform.legacy.rtc = 0;
x86_platform.legacy.i8042 = X86_LEGACY_I8042_PLATFORM_ABSENT;
break;
}
if (x86_platform.set_legacy_features)
x86_platform.set_legacy_features();
}
bool __init x86_pnpbios_disabled(void)
{
return x86_platform.legacy.devices.pnpbios == 0;
}
#if defined(CONFIG_PNPBIOS)
bool __init arch_pnpbios_disabled(void)
{
return x86_pnpbios_disabled();
}
#endif