From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751230AbeC2PIU (ORCPT ); Thu, 29 Mar 2018 11:08:20 -0400 Received: from mga09.intel.com ([134.134.136.24]:54487 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750708AbeC2PIT (ORCPT ); Thu, 29 Mar 2018 11:08:19 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.48,376,1517904000"; d="scan'208";a="41807443" From: Anshuman Gupta To: tglx@linutronix.de Cc: x86@kernel.org, mingo@redhat.com, hpa@zytor.com, rjw@rjwysocki.net, andriy.shevchenko@linux.intel.com, alan@linux.intel.com, linux-kernel@vger.kernel.org, rajneesh.bhardwaj@intel.com, anshuman.gupta@intel.com Subject: [PATCH v4] x86: i8237: Register based on FADT legacy boot flag Date: Thu, 29 Mar 2018 20:36:55 +0530 Message-Id: <1522336015-22994-1-git-send-email-anshuman.gupta@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Rajneesh Bhardwaj >>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. https://github.com/coreboot/coreboot/blob/05132707ca1e13a11cd13c77326bc65011b09feb/src/soc/intel/skylake/acpi.c#L271 Please refer to chapter 21 of 6th Generation Intel® Core™ Processor Platform Controller Hub Family: BIOS Specification. https://www.intel.in/content/www/in/en/embedded/products/skylake/u-mobile/software-and-drivers.html Cc: Alan Cox Reviewed-by: Andy Shevchenko Signed-off-by: Anshuman Gupta Signed-off-by: Rajneesh Bhardwaj --- Changes in v4: * Modified the commit message about cut-off date year 2017. Changes in v3: * Added x86_pnpbios_disabled and using it instead of pnpbios. * Modified the commit message. Changes in v2: * changed to dma_inb() --- arch/x86/include/asm/x86_init.h | 1 + arch/x86/kernel/i8237.c | 25 +++++++++++++++++++++++++ arch/x86/kernel/platform-quirks.c | 7 ++++++- 3 files changed, 32 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h index fc2f082..b6ceac0 100644 --- a/arch/x86/include/asm/x86_init.h +++ b/arch/x86/include/asm/x86_init.h @@ -286,6 +286,7 @@ extern struct x86_msi_ops x86_msi; extern struct x86_io_apic_ops x86_io_apic_ops; extern void x86_early_init_platform_quirks(void); +extern bool x86_pnpbios_disabled(void); extern void x86_init_noop(void); extern void x86_init_uint_noop(unsigned int unused); diff --git a/arch/x86/kernel/i8237.c b/arch/x86/kernel/i8237.c index 8eeaa81..0a3e70f 100644 --- a/arch/x86/kernel/i8237.c +++ b/arch/x86/kernel/i8237.c @@ -9,10 +9,12 @@ * your option) any later version. */ +#include #include #include #include +#include /* * 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; } diff --git a/arch/x86/kernel/platform-quirks.c b/arch/x86/kernel/platform-quirks.c index 235fe60..b348a67 100644 --- a/arch/x86/kernel/platform-quirks.c +++ b/arch/x86/kernel/platform-quirks.c @@ -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 -- 2.7.4