From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D44C2C433F5 for ; Thu, 7 Apr 2022 01:24:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238382AbiDGB03 (ORCPT ); Wed, 6 Apr 2022 21:26:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60570 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239762AbiDGBT3 (ORCPT ); Wed, 6 Apr 2022 21:19:29 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7B24E1AF7FA; Wed, 6 Apr 2022 18:15:00 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 19DFC61DB0; Thu, 7 Apr 2022 01:15:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 279CFC385A1; Thu, 7 Apr 2022 01:14:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1649294099; bh=9+gK3EfVe4i70R1qceW78UceKAnxu03KRWGw5bq5nDs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mOqOvjtTRh4z0CLUrbVay4Y8Jp4NWXMWfoS1zOv8gX9gxYePsEw55iTX73/RNFA8B 5EgWXXItieippc+YaLgbQymemTViYumCjdv9jPEd1Qy/F3gaa13jEG9Qc0wvy/zEy+ BUDnKQW154Rzb5Q+BVrEVIcGUPBTx+w2yDGQYDk4yioBn1LRwfIxR6t7polqha5PyB C1jIKM3ErhTwSs8oR8ZP5+6RFD1bBHXJs1KQD5+I7jXK46rVqV2xBEB+s41o16hRtI syubsw3dglaoBn253b1Wcy4XzGlVYnpAWBVJZcib+bogPZv7BUkq5WoXTuEr2VV82X InS+vhPws09kg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Mario Limonciello , Jinke Fan , Mikhail Gavrilov , Raul E Rangel , Alexandre Belloni , Sasha Levin , a.zummo@towertech.it, mat.jonczyk@o2.pl, dan.carpenter@oracle.com, linux-rtc@vger.kernel.org Subject: [PATCH AUTOSEL 5.10 18/25] rtc: mc146818-lib: Fix the AltCentury for AMD platforms Date: Wed, 6 Apr 2022 21:14:06 -0400 Message-Id: <20220407011413.114662-18-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220407011413.114662-1-sashal@kernel.org> References: <20220407011413.114662-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mario Limonciello [ Upstream commit 3ae8fd41573af4fb3a490c9ed947fc936ba87190 ] Setting the century forward has been failing on AMD platforms. There was a previous attempt at fixing this for family 0x17 as part of commit 7ad295d5196a ("rtc: Fix the AltCentury value on AMD/Hygon platform") but this was later reverted due to some problems reported that appeared to stem from an FW bug on a family 0x17 desktop system. The same comments mentioned in the previous commit continue to apply to the newer platforms as well. ``` MC146818 driver use function mc146818_set_time() to set register RTC_FREQ_SELECT(RTC_REG_A)'s bit4-bit6 field which means divider stage reset value on Intel platform to 0x7. While AMD/Hygon RTC_REG_A(0Ah)'s bit4 is defined as DV0 [Reference]: DV0 = 0 selects Bank 0, DV0 = 1 selects Bank 1. Bit5-bit6 is defined as reserved. DV0 is set to 1, it will select Bank 1, which will disable AltCentury register(0x32) access. As UEFI pass acpi_gbl_FADT.century 0x32 (AltCentury), the CMOS write will be failed on code: CMOS_WRITE(century, acpi_gbl_FADT.century). Correct RTC_REG_A bank select bit(DV0) to 0 on AMD/Hygon CPUs, it will enable AltCentury(0x32) register writing and finally setup century as expected. ``` However in closer examination the change previously submitted was also modifying bits 5 & 6 which are declared reserved in the AMD documentation. So instead modify just the DV0 bank selection bit. Being cognizant that there was a failure reported before, split the code change out to a static function that can also be used for exclusions if any regressions such as Mikhail's pop up again. Cc: Jinke Fan Cc: Mikhail Gavrilov Link: https://lore.kernel.org/all/CABXGCsMLob0DC25JS8wwAYydnDoHBSoMh2_YLPfqm3TTvDE-Zw@mail.gmail.com/ Link: https://www.amd.com/system/files/TechDocs/51192_Bolton_FCH_RRG.pdf Signed-off-by: Raul E Rangel Signed-off-by: Mario Limonciello Signed-off-by: Alexandre Belloni Link: https://lore.kernel.org/r/20220111225750.1699-1-mario.limonciello@amd.com Signed-off-by: Sasha Levin --- drivers/rtc/rtc-mc146818-lib.c | 16 +++++++++++++++- include/linux/mc146818rtc.h | 2 ++ 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c index 5add637c9ad2..b036ff33fbe6 100644 --- a/drivers/rtc/rtc-mc146818-lib.c +++ b/drivers/rtc/rtc-mc146818-lib.c @@ -99,6 +99,17 @@ unsigned int mc146818_get_time(struct rtc_time *time) } EXPORT_SYMBOL_GPL(mc146818_get_time); +/* AMD systems don't allow access to AltCentury with DV1 */ +static bool apply_amd_register_a_behavior(void) +{ +#ifdef CONFIG_X86 + if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || + boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) + return true; +#endif + return false; +} + /* Set the current date and time in the real time clock. */ int mc146818_set_time(struct rtc_time *time) { @@ -172,7 +183,10 @@ int mc146818_set_time(struct rtc_time *time) save_control = CMOS_READ(RTC_CONTROL); CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL); save_freq_select = CMOS_READ(RTC_FREQ_SELECT); - CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT); + if (apply_amd_register_a_behavior()) + CMOS_WRITE((save_freq_select & ~RTC_AMD_BANK_SELECT), RTC_FREQ_SELECT); + else + CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT); #ifdef CONFIG_MACH_DECSTATION CMOS_WRITE(real_yrs, RTC_DEC_YEAR); diff --git a/include/linux/mc146818rtc.h b/include/linux/mc146818rtc.h index 0661af17a758..1e0205811394 100644 --- a/include/linux/mc146818rtc.h +++ b/include/linux/mc146818rtc.h @@ -86,6 +86,8 @@ struct cmos_rtc_board_info { /* 2 values for divider stage reset, others for "testing purposes only" */ # define RTC_DIV_RESET1 0x60 # define RTC_DIV_RESET2 0x70 + /* In AMD BKDG bit 5 and 6 are reserved, bit 4 is for select dv0 bank */ +# define RTC_AMD_BANK_SELECT 0x10 /* Periodic intr. / Square wave rate select. 0=none, 1=32.8kHz,... 15=2Hz */ # define RTC_RATE_SELECT 0x0F -- 2.35.1