x86/i8237: Register device based on FADT legacy boot flag (f79b1c57) · Commits · 戴 / test

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

arch/x86/include/asm/x86_init.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -301,5 +301,6 @@ extern struct x86_apic_ops x86_apic_ops;
		extern void x86_early_init_platform_quirks(void);
		extern void x86_init_noop(void);
		extern void x86_init_uint_noop(unsigned int unused);
		extern bool x86_pnpbios_disabled(void);

		#endif

arch/x86/kernel/i8237.c

+25 −0

Original line number	Diff line number	Diff line
		@@ -9,10 +9,12 @@
		* your option) any later version.
		*/

		#include <linux/dmi.h>
		#include <linux/init.h>
		#include <linux/syscore_ops.h>

		#include <asm/dma.h>
		#include <asm/x86_init.h>

		/*
		* This module just handles suspend/resume issues with the
		@@ -49,6 +51,29 @@ static struct syscore_ops i8237_syscore_ops = {

		static int __init i8237A_init_ops(void)
		{
		/*
		* From SKL PCH onwards, the legacy DMA device is removed in which the
		* I/O ports (81h-83h, 87h, 89h-8Bh, 8Fh) related to it are removed
		* as well. All removed ports must return 0xff for a inb() request.
		*
		* Note: DMA_PAGE_2 (port 0x81) should not be checked for detecting
		* the presence of DMA device since it may be used by BIOS to decode
		* LPC traffic for POST codes. Original LPC only decodes one byte of
		* port 0x80 but some BIOS may choose to enhance PCH LPC port 0x8x
		* decoding.
		*/
		if (dma_inb(DMA_PAGE_0) == 0xFF)
		return -ENODEV;

		/*
		* It is not required to load this driver as newer SoC may not
		* support 8237 DMA or bus mastering from LPC. Platform firmware
		* must announce the support for such legacy devices via
		* ACPI_FADT_LEGACY_DEVICES field in FADT table.
		*/
		if (x86_pnpbios_disabled() && dmi_get_bios_year() >= 2017)
		return -ENODEV;

		register_syscore_ops(&i8237_syscore_ops);
		return 0;
		}

arch/x86/kernel/platform-quirks.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -33,9 +33,14 @@ void __init x86_early_init_platform_quirks(void)
		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_platform.legacy.devices.pnpbios == 0;
		return x86_pnpbios_disabled();
		}
		#endif

Admin message