From patchwork Mon Aug 26 13:25:53 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 11114609 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 66EB71399 for ; Mon, 26 Aug 2019 13:26:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4622A21872 for ; Mon, 26 Aug 2019 13:26:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="SxWguzeH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732419AbfHZN0b (ORCPT ); Mon, 26 Aug 2019 09:26:31 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:35596 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732403AbfHZN00 (ORCPT ); Mon, 26 Aug 2019 09:26:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender :Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From :Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=MhfKilNLV8AdxkyYpV9V+99YpggpHbv15IYon9mhMkc=; b=SxWguzeHjibJiQGTh0enGJ7wsj xvlWsmuxilsSrybCT7ApvIPfTJthkTEJChIJ5pY9DHIsQGjUN67v8cKOOKr5a0uXhM5HM4z32vow4 bkkZjRbgFpCc/BYTH1TR2Srt2asiNr4QwjlKzC6thdTiNry7uant3AU9xHnoI8haOOP/qM8zbiqxw 4HlaZ9eaMXY9Je+6oKpIzLdltUVMmtCOJrHiTM/zTsoJ2sL1u6Gn862HOqAy+cr2ZFt3K9eB+DHlR YzntowaXSIiZlnQk9a3lTajwZqbRPQp/EZ6iFMq2aXPq9PasHkqpCJwWzyHeA9WB3ILK9MurfmZqm +7QSFpkQ==; Received: from clnet-p19-102.ikbnet.co.at ([83.175.77.102] helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1i2F0h-0007zP-RH; Mon, 26 Aug 2019 13:26:16 +0000 From: Christoph Hellwig To: iommu@lists.linux-foundation.org Cc: Guan Xuetao , Shawn Anastasio , Russell King , Catalin Marinas , Will Deacon , Robin Murphy , Paul Burton , James Hogan , Geert Uytterhoeven , linuxppc-dev@lists.ozlabs.org, linux-mips@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-m68k@lists.linux-m68k.org, linux-kernel@vger.kernel.org Subject: [PATCH 6/6] MIPS: document mixing "slightly different CCAs" Date: Mon, 26 Aug 2019 15:25:53 +0200 Message-Id: <20190826132553.4116-7-hch@lst.de> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190826132553.4116-1-hch@lst.de> References: <20190826132553.4116-1-hch@lst.de> MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org Based on an email from Paul Burton, quoting section 4.8 "Cacheability and Coherency Attributes and Access Types" of "MIPS Architecture Volume 1: Introduction to the MIPS32 Architecture" (MD00080, revision 6.01). Signed-off-by: Christoph Hellwig Acked-by: Paul Burton --- arch/mips/Kconfig | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index fc88f68ea1ee..aff1cadeea43 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -1119,6 +1119,13 @@ config DMA_PERDEV_COHERENT config DMA_NONCOHERENT bool + # + # MIPS allows mixing "slightly different" Cacheability and Coherency + # Attribute bits. It is believed that the uncached access through + # KSEG1 and the implementation specific "uncached accelerated" used + # by pgprot_writcombine can be mixed, and the latter sometimes provides + # significant advantages. + # select ARCH_HAS_DMA_WRITE_COMBINE select ARCH_HAS_SYNC_DMA_FOR_DEVICE select ARCH_HAS_UNCACHED_SEGMENT