From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f43.google.com (mail-wm1-f43.google.com [209.85.128.43]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 184472FB6 for ; Wed, 19 May 2021 07:15:10 +0000 (UTC) Received: by mail-wm1-f43.google.com with SMTP id o127so6660056wmo.4 for ; Wed, 19 May 2021 00:15:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=brainfault-org.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=9okw0AivC/GodUAOgdSjrzNrGvlF7i2iJnuU6Q7Ckhk=; b=GLdq3bNPUG1jVbmGuXT/73WV/H4ct0JC+JPyO1eIGy+uxrXeIrrgUTBkgOyB79PHc7 wLFK19VrpLW3+QR7uumz7VfegumO/03BPjeaHthtleLjPv4rR5sZsZKmnwKaMZ0UMMQE gr/wpNE/p3phdRl/HBhMBnnG7Ceqfv4Un6Qh9OMLUWnILbaOcsufq7QT6gVJNkALrDj5 LvEedY1AAT0Wpovo/BsutzLeeNlF70WhAFXjf5wfegQAs7idnoCE+88T76OnTfUMjnqY mZBt11ZLbg81ZNLfNeOqHoJde6wljGw5DprysPeWSQuaCaOg7bKP+7E2aaqYKQ3qBy0R wFLA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=9okw0AivC/GodUAOgdSjrzNrGvlF7i2iJnuU6Q7Ckhk=; b=LqDdp4UXAXuxAqSX2wxZJRpNBLbrh1jZ2kqWwJ0ECh40iiiA2MNJRcvBi8YGSDRagb CwdN895e98qAPiMPvlweJOajzLwZN8JnYWhgK53b+Jscf5nzhSevKVY5yY2RXxcwH29u u0HjLYHC7yU3o5MoNPuDPORtW28XqDA5e/W1aDaHOjj+BhEL7q3lAUeTSRD3dP2JnpMQ 52/Y4Njt4h3eofBy73xiUA2UBgJO3Gug+RVaLac+XJ8opeWUEo0MXfnwNp7JuAgLqnzC 8IsXV9IBJQu3mKVpZyaWPuja6qBuAw2oc1Z1z3W6vVNXDtP6ycvvwTg9c9wVP/HCoq/i vfuQ== X-Gm-Message-State: AOAM532UAXXncdYgxWCxFiHZOjxNJPBBrXKP/5ADZSWXC3fRvLGBdx5q Lmm8Mhhr7GjrqSJLwrMwxXg0NJBXS8v8sHSxQsqVkA== X-Google-Smtp-Source: ABdhPJw/naptBUbx4b3ptbfbXhmKN+TgrAcgi05rNO45VadkiPEcCxSc5SrssSarObHWl3KVpfRHtcRUN81TCIYDW3E= X-Received: by 2002:a1c:4e0b:: with SMTP id g11mr9882524wmh.3.1621408508509; Wed, 19 May 2021 00:15:08 -0700 (PDT) X-Mailing-List: linux-sunxi@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <1621400656-25678-1-git-send-email-guoren@kernel.org> <20210519052048.GA24853@lst.de> <20210519060617.GA28397@lst.de> <20210519065431.GB3076809@x1> In-Reply-To: <20210519065431.GB3076809@x1> From: Anup Patel Date: Wed, 19 May 2021 12:44:55 +0530 Message-ID: Subject: Re: [PATCH RFC 0/3] riscv: Add DMA_COHERENT support To: Drew Fustini Cc: Christoph Hellwig , Guo Ren , Anup Patel , Palmer Dabbelt , wefu@redhat.com, =?UTF-8?B?V2VpIFd1ICjlkLTkvJ8p?= , linux-riscv , Linux Kernel Mailing List , linux-arch , linux-sunxi@lists.linux.dev, Guo Ren , Paul Walmsley Content-Type: text/plain; charset="UTF-8" On Wed, May 19, 2021 at 12:24 PM Drew Fustini wrote: > > On Wed, May 19, 2021 at 08:06:17AM +0200, Christoph Hellwig wrote: > > On Wed, May 19, 2021 at 02:05:00PM +0800, Guo Ren wrote: > > > Since the existing RISC-V ISA cannot solve this problem, it is better > > > to provide some configuration for the SOC vendor to customize. > > > > We've been talking about this problem for close to five years. So no, > > if you don't manage to get the feature into the ISA it can't be > > supported. > > Isn't it a good goal for Linux to support the capabilities present in > the SoC that a currently being fab'd? > > I believe the CMO group only started last year [1] so the RV64GC SoCs > that are going into mass production this year would not have had the > opporuntiy of utilizing any RISC-V ISA extension for handling cache > management. The current Linux RISC-V policy is to only accept patches for frozen or ratified ISA specs. (Refer, Documentation/riscv/patch-acceptance.rst) This means even if emulate CMO instructions in OpenSBI, the Linux patches won't be taken by Palmer because CMO specification is still in draft stage. Also, we all know how much time it takes for RISCV international to freeze some spec. Judging by that we are looking at another 3-4 years at minimum. Regards, Anup