Commit 3eb616b2 authored by Hans de Goede's avatar Hans de Goede Committed by Rafael J. Wysocki
Browse files

x86/PCI: revert "Ignore E820 reservations for bridge windows on newer systems" 

Commit 7f7b4236 ("x86/PCI: Ignore E820 reservations for bridge windows
on newer systems") fixes the touchpad not working on laptops like
the Lenovo IdeaPad 3 15IIL05 and the Lenovo IdeaPad 5 14IIL05, as well as
fixing thunderbolt hotplug issues on the Lenovo Yoga C940.

Unfortunately it turns out that this is causing issues with suspend/resume
on Lenovo ThinkPad X1 Carbon Gen 2 laptops. So, per the no regressions
policy, rever this. Note I'm looking into another fix for the issues this
fixed.

Fixes: 7f7b4236 ("x86/PCI: Ignore E820 reservations for bridge windows on newer systems")
BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=2029207


Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 7f7b4236

arch/x86/kernel/resource.c

+1 −22
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

#include <linux/dmi.h>

#include <linux/ioport.h>

#include <asm/e820/api.h>
@@ -24,31 +23,11 @@ static void resource_clip(struct resource *res, resource_size_t start, 
		res->start = end + 1;

}



/*

 * Some BIOS-es contain a bug where they add addresses which map to

 * system RAM in the PCI host bridge window returned by the ACPI _CRS

 * method, see commit 4dc2287c1805 ("x86: avoid E820 regions when

 * allocating address space"). To avoid this Linux by default excludes

 * E820 reservations when allocating addresses since 2010.

 * In 2019 some systems have shown-up with E820 reservations which cover

 * the entire _CRS returned PCI host bridge window, causing all attempts

 * to assign memory to PCI BARs to fail if Linux uses E820 reservations.

 *

 * Ideally Linux would fully stop using E820 reservations, but then

 * the old systems this was added for will regress.

 * Instead keep the old behavior for old systems, while ignoring the

 * E820 reservations for any systems from now on.

 */

static void remove_e820_regions(struct resource *avail)

{

	int i, year = dmi_get_bios_year();

	int i;

	struct e820_entry *entry;



	if (year >= 2018)

		return;



	pr_info_once("PCI: Removing E820 reservations from host bridge windows\n");



	for (i = 0; i < e820_table->nr_entries; i++) {

		entry = &e820_table->entries[i];