From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753358AbcERNuu (ORCPT ); Wed, 18 May 2016 09:50:50 -0400 Received: from mout.kundenserver.de ([217.72.192.73]:60336 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753324AbcERNus (ORCPT ); Wed, 18 May 2016 09:50:48 -0400 From: Arnd Bergmann To: Catalin Marinas Cc: linux-arm-kernel@lists.infradead.org, Will Deacon , Alexander Graf , linux-kernel@vger.kernel.org, Sinan Kaya , Eric Anholt Subject: Re: [PATCH] arm64: Allow for different DMA and CPU bus offsets Date: Wed, 18 May 2016 15:50:02 +0200 Message-ID: <30915363.3kcXpGGcy5@wuerfel> User-Agent: KMail/4.11.5 (Linux/3.16.0-10-generic; KDE/4.11.5; x86_64; ; ) In-Reply-To: <20160518134554.GF22378@e104818-lin.cambridge.arm.com> References: <1463563981-69722-1-git-send-email-agraf@suse.de> <12218676.p29ELivsix@wuerfel> <20160518134554.GF22378@e104818-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:FLu3KKRfaASyj3smo4vgx4hVd25BZqqyg6fiqHd9UV2si3lp5MX O6CftKwwh5hrC6EFU0Kq2AW7/0erTxZyrOFdj2WqAIdewJ1a/fhxvsH+HmcGkKQ5NVnoXQc gAJ/9AyEuERK75Zx39zZfQVCfh0XKeQMmux2C6Ypva8jUAbo3uHcpDwtmJM80rOYgA/iLKk QAOjdzoIfTlFXKjFplrSQ== X-UI-Out-Filterresults: notjunk:1;V01:K0:hJz11XZCCwI=:v0vbZyTmScqT54L6CE31+I r5EuVEAI2dlmqDWrHVSUxpAymyKp0Iv+g6n20UZIzXTvc8mj5I9Aj0iujokCgHN9ngWqAsL5z W3FsuuKUWGHzJuYHBSj0skCmHdyIt7/SwSvsI0yJRYCTz92YBVa0qn1jOhZBrwHlJ8pr+SMAB 7lr0E7mcCeio0V9uZspXbFlxoEJnSowal+dG7zTUHbC43KdeH/cxgQBIxIs9tpKEJyhNL5hqk 9oXC0Mt+n1eFM7M4eqXPSrrQelDBBt3OQ/SVcy75aT74Vo6k7BIP4099PZ2FUsNEk1+BDcR/7 dxIoxgTSQQni3zRIgRlFwsfkN4erB0qMf0uy3E/KA2aQi9ipsoedwO4kPIwnMnDh3SQ74FoRu 6diytq6kImDqeammavTFRxR89hC8dvuiO8dL/DMgVMyOH9sTsG6uVJx78a5o+cir7VW6oOL2t Zdi4eVQ7ngZinqI/UlgU5PQH27fHJhgiC0ZQvRQLP6w+nICnczxMpwMVTp8Wk8XKwJexEMVaW J2b0ooc48lqSP8gQ/0r2qSWfeXPWLQFIysXpcsywSmhNzs62WE6atxMYlkB+X3VodT2m+bSVC Li8nJA3MNJ/WPL2reNf0lFpaHJfBLo0NCFMRwsxiQfpXxOF+wupiIHD/s0Whx8sLVjTEYqdrw 3yxK2DhsWA4u27Ofyir65iThW53gvndApTrzlcjnZC6X83Uc5ImoHkShLMDJ6PqZFxJoyPx9u chJuHAGN/ejBL1mnSaw87qyjW8rzqHZdq9Vdig== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday 18 May 2016 14:45:55 Catalin Marinas wrote: > On Wed, May 18, 2016 at 12:52:28PM +0200, Arnd Bergmann wrote: > > On Wednesday 18 May 2016 11:33:01 Alexander Graf wrote: > > > diff --git a/arch/arm64/include/asm/dma-mapping.h b/arch/arm64/include/asm/dma-mapping.h > > > index ba437f0..67bf8e1 100644 > > > --- a/arch/arm64/include/asm/dma-mapping.h > > > +++ b/arch/arm64/include/asm/dma-mapping.h > > > @@ -66,12 +66,16 @@ static inline bool is_device_dma_coherent(struct device *dev) > > > > > > static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr) > > > { > > > - return (dma_addr_t)paddr; > > > + dma_addr_t dev_addr = (dma_addr_t)paddr; > > > + > > > + return dev_addr - (dma_addr_t)__pfn_to_phys(dev->dma_pfn_offset); > > > } > > > > > > static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dev_addr) > > > { > > > - return (phys_addr_t)dev_addr; > > > + phys_addr_t paddr = (phys_addr_t)dev_addr; > > > + > > > + return paddr + __pfn_to_phys(dev->dma_pfn_offset); > > > } > > > > > > > The patch looks ok overall, but I think it's better to use an open-coded > > shift instead of __pfn_to_phys/__pfn_to_phys here: those helpers convert > > between actual page frame numbers and addresses, which may not always > > be a 1:1 relationship, e.g. if someone wants to work around the crazy > > "Principles of ARM Memory Maps White Paper" layout. > > Nitpick: Even better to use the PFN_PHYS() macro as it matches the > PFN_DOWN() in of_dma_configure(). I can fix it up when applying. > > I'd probably avoid that for the same reason as avoiding __pfn_to_phys. In practice all three methods do the same thing for now, and if someone wanted to change one, they'd also have to audit all the existing users. Arnd