From mboxrd@z Thu Jan 1 00:00:00 1970 From: Laura Abbott Subject: Re: [PATCH V3] of: Set the DMA mask to 64 bits when dma_addr_t is 64-bits Date: Mon, 08 Jul 2013 19:38:58 -0700 Message-ID: <51DB77C2.4060705@codeaurora.org> References: <1367008266-1431-1-git-send-email-lauraa@codeaurora.org> <517AF270.8040106@gmail.com> <51D71F81.5090503@codeaurora.org> <20130708104254.GS24642@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130708104254.GS24642-l+eeeJia6m9vn6HldHNs0ANdhmdF6hFW@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Sender: "devicetree-discuss" To: Russell King - ARM Linux Cc: Ming Lei , devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Catalin Marinas List-Id: devicetree@vger.kernel.org On 7/8/2013 3:42 AM, Russell King - ARM Linux wrote: >> >> The problem is the way the arm_dma_limit is set up, all dma allocations >> are currently broken regardless of if the actual device supports 64-bit >> addresses or not. > > Please explain this statement. > The statement was a bit shortsighted given recent discussions. My point was that on LPAE systems right now without ZONE_DMA, the allocation fails by default (i.e. no call to set_mask) even if the device could support 64-bit physical memory. Based on this thread though, drivers should stop assuming the dma_mask will be set up properly and always set the mask appropriately. The conclusion also seems to be that if devices on an LPAE system can't handle > 32-bit addresses and want to limit via mask, ZONE_DMA must be set up. Please correct me if I misunderstood anything. Thanks, Laura -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation