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 DAB2CCDB46E for ; Thu, 12 Oct 2023 14:50:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378991AbjJLOuA (ORCPT ); Thu, 12 Oct 2023 10:50:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45604 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233260AbjJLOt6 (ORCPT ); Thu, 12 Oct 2023 10:49:58 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A45ABD6 for ; Thu, 12 Oct 2023 07:49:56 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0FDD7C433C8; Thu, 12 Oct 2023 14:49:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697122196; bh=WqvrIw3PkN3YYn1wVpzhO2s/Fo/gP7GkrtfWS3/rmZA=; h=From:To:Cc:Subject:Date:From; b=enA3mxvR1zssOjbMXwEkzY9UzGSeZWl8gFLi51c+AwxhAtznYQ+wxowCIkgqt5gCu SerfeCocbYsySI2epiFJ4mrEWZN5FY9S6ql3+YOJlO2P+YnDesvFUL0aIiELNvIhPW 7/eh5/rZebfsGWqxsyNRvXSmvH8qPbT49rtiagODqPdOyuIaBxjt1f5jxLkbNsTXwv gXuzIkLSbHF7y1SThaLtR95hjW7xTIPdcQovCr8Iqx8zEY0FvjZZx3AHNzukqY20JJ xE/wAG61GALMnatOvFTjz+SvTEzRmJ+sABCXrE6y3VK97EWnpuM3eNNl0J6faSiyKl F2i/sBbGz49eA== From: Jisheng Zhang To: Paul Walmsley , Palmer Dabbelt , Albert Ou Cc: Guo Ren , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 0/2] riscv: errata: thead: use riscv_nonstd_cache_ops for CMO Date: Thu, 12 Oct 2023 22:37:44 +0800 Message-Id: <20231012143746.454-1-jszhang@kernel.org> X-Mailer: git-send-email 2.40.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Previously, we use alternative mechanism to dynamically patch the CMO operations for THEAD C906/C910 during boot for performance reason. But as pointed out by Arnd, "there is already a significant cost in accessing the invalidated cache lines afterwards, which is likely going to be much higher than the cost of an indirect branch". And indeed, there's no performance difference with GMAC and EMMC per my test on Sipeed Lichee Pi 4A board. Use riscv_nonstd_cache_ops for THEAD C906/C910 CMO to simplify the alternative code, and to acchieve Arnd's goal -- "I think moving the THEAD ops at the same level as all nonstandard operations makes sense, but I'd still leave CMO as an explicit fast path that avoids the indirect branch. This seems like the right thing to do both for readability and for platforms on which the indirect branch has a noticeable overhead." To make bisect easy, I use two patches here: patch1 does the conversion which just mimics current CMO behavior via. riscv_nonstd_cache_ops, I assume no functionalities changes. patch2 uses T-HEAD PA based CMO instructions so that we don't need to covert PA to VA. Hi Guo, I didn't use wback_inv for wback as you suggested during v1 reviewing, this can be left as future optimizations. Thanks since v3: - collect Reviewed-by tag since v2: - collect Reviewed-by tag (but missed them in fact) - fix typo since v1: - collect Tested-by tag - add patch2 to use T-HEAD PA based CMO instructions. Jisheng Zhang (2): riscv: errata: thead: use riscv_nonstd_cache_ops for CMO riscv: errata: thead: use pa based instructions for CMO arch/riscv/Kconfig.errata | 1 + arch/riscv/errata/thead/errata.c | 69 +++++++++++++++++++++++++++- arch/riscv/include/asm/errata_list.h | 50 +++----------------- 3 files changed, 74 insertions(+), 46 deletions(-) -- 2.40.1