From nobody Sun Feb 8 23:24:46 2026 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 656BEEB64DC for ; Tue, 11 Jul 2023 13:34:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233025AbjGKNeS (ORCPT ); Tue, 11 Jul 2023 09:34:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51258 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233023AbjGKNeN (ORCPT ); Tue, 11 Jul 2023 09:34:13 -0400 Received: from mail-ed1-x534.google.com (mail-ed1-x534.google.com [IPv6:2a00:1450:4864:20::534]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 22A8110C7 for ; Tue, 11 Jul 2023 06:34:08 -0700 (PDT) Received: by mail-ed1-x534.google.com with SMTP id 4fb4d7f45d1cf-51e46e83d7fso4728009a12.1 for ; Tue, 11 Jul 2023 06:34:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1689082447; x=1691674447; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=rEE57oj+GdsJXanw66t6tys98dAd0Zr2j6aIYgyrMwY=; b=g/WuLHQmL7CPdZ+Ok7EIf7d1Xu/fG+L/P6L7zVdUBdCdF3Ez6u2boNDYnk61d0rIwj CMhftbvXawRc4ut4OCxgXIiUPgbP/rsImTOz2B8HxmeRaq9eF6BKXeU0OJDsQt/9fq4b Omv7FpHIZKArHhSa7+IyI4hQwJ3p5iJHaq3UHvNC2phwTCWfaEMyiofpiQ6MctE1k0/r O8P6NU63aexh8ylJO9t0TTSgQDsNUhjUAKDpP8Cr1C0QRUBHHVSDQ2hL1x8j9PzOh30Z rAe63UFW8+oZbcuikCVhHBL6m6zB9HM0St0jXu6KU6VY74MNzuetN4VKurTuF6z6CUsW 0GWA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689082447; x=1691674447; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=rEE57oj+GdsJXanw66t6tys98dAd0Zr2j6aIYgyrMwY=; b=NmcVs6x27TUslyTu8DlRSvRk1EK4Q7zZv3EH8OdQv3IO47bTio8FLSzVCBe3fEEY/E 2pRegmQtcMPs73WnKoDYbWeDmq0fLMsg2MChDsRsQYfhjTV0xzThl+AdTnC18ZE9Zf0r eOMKZQkACqSZA+o/r7emeiy/Fzoc7yV2TICx4Dxqqiy0ipYQOQY5weOkxr2ItKVE7mho hE0ieA/qwR87pwibb3D5gRBjUHCfUDLgLsdGLjFIixnYZINvKePfVRMahE7ckf1uQQZL SQzw2lB8LPjgL5iDg65VhhEvF9Db40RNeIPzzvtCGENKAF1ZegEMhjM3mSHwva3z9+eQ F0ZQ== X-Gm-Message-State: ABy/qLYKNg8m/mPhJcQO+NJIBB3fOO5C8DxAH8Xv4hKdgFVIZB4t7/nu JkieyDIyhjO/PGU7G40huYw= X-Google-Smtp-Source: APBJJlECFO/61hgLZW4KZGoE5ATuuGswvkOlnPXeP+0NaXUEhKoKs3y0HJMojjzcdAiRR0YaNxWizw== X-Received: by 2002:a05:6402:6cf:b0:51e:fa7:a292 with SMTP id n15-20020a05640206cf00b0051e0fa7a292mr14655910edy.12.1689082446838; Tue, 11 Jul 2023 06:34:06 -0700 (PDT) Received: from andrea.ba.rivosinc.com ([2.199.74.220]) by smtp.gmail.com with ESMTPSA id v15-20020a056402184f00b0051df6c2bb7asm1276862edy.38.2023.07.11.06.34.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Jul 2023 06:34:06 -0700 (PDT) From: Andrea Parri To: Paul Walmsley , Palmer Dabbelt , Albert Ou Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Andrea Parri Subject: [PATCH 1/2] riscv,mmio: Fix readX()-to-delay() ordering Date: Tue, 11 Jul 2023 15:33:47 +0200 Message-Id: <20230711133348.151383-2-parri.andrea@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230711133348.151383-1-parri.andrea@gmail.com> References: <20230711133348.151383-1-parri.andrea@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Section 2.1 of the Platform Specification [1] states: Unless otherwise specified by a given I/O device, I/O devices are on ordering channel 0 (i.e., they are point-to-point strongly ordered). which is not sufficient to guarantee that a readX() by a hart completes before a subsequent delay() on the same hart (cf. memory-barriers.txt, "Kernel I/O barrier effects"). Set the I(nput) bit in __io_ar() to restore the ordering, align inline comments. [1] https://github.com/riscv/riscv-platform-specs Signed-off-by: Andrea Parri --- arch/riscv/include/asm/mmio.h | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/arch/riscv/include/asm/mmio.h b/arch/riscv/include/asm/mmio.h index aff6c33ab0c08..4c58ee7f95ecf 100644 --- a/arch/riscv/include/asm/mmio.h +++ b/arch/riscv/include/asm/mmio.h @@ -101,9 +101,9 @@ static inline u64 __raw_readq(const volatile void __iom= em *addr) * Relaxed I/O memory access primitives. These follow the Device memory * ordering rules but do not guarantee any ordering relative to Normal mem= ory * accesses. These are defined to order the indicated access (either a re= ad or - * write) with all other I/O memory accesses. Since the platform specifica= tion - * defines that all I/O regions are strongly ordered on channel 2, no expl= icit - * fences are required to enforce this ordering. + * write) with all other I/O memory accesses to the same peripheral. Since= the + * platform specification defines that all I/O regions are strongly ordere= d on + * channel 0, no explicit fences are required to enforce this ordering. */ /* FIXME: These are now the same as asm-generic */ #define __io_rbr() do {} while (0) @@ -125,14 +125,14 @@ static inline u64 __raw_readq(const volatile void __i= omem *addr) #endif =20 /* - * I/O memory access primitives. Reads are ordered relative to any - * following Normal memory access. Writes are ordered relative to any prior - * Normal memory access. The memory barriers here are necessary as RISC-V + * I/O memory access primitives. Reads are ordered relative to any follow= ing + * Normal memory read and delay() loop. Writes are ordered relative to any + * prior Normal memory write. The memory barriers here are necessary as R= ISC-V * doesn't define any ordering between the memory space and the I/O space. */ #define __io_br() do {} while (0) -#define __io_ar(v) __asm__ __volatile__ ("fence i,r" : : : "memory") -#define __io_bw() __asm__ __volatile__ ("fence w,o" : : : "memory") +#define __io_ar(v) ({ __asm__ __volatile__ ("fence i,ir" : : : "memory"); = }) +#define __io_bw() ({ __asm__ __volatile__ ("fence w,o" : : : "memory"); }) #define __io_aw() mmiowb_set_pending() =20 #define readb(c) ({ u8 __v; __io_br(); __v =3D readb_cpu(c); __io_ar(__v)= ; __v; }) --=20 2.34.1