From mboxrd@z Thu Jan 1 00:00:00 1970 From: Timur Tabi Subject: Re: [PATCH] [v6] net: emac: emac gigabit ethernet controller driver Date: Wed, 29 Jun 2016 10:10:59 -0500 Message-ID: <5773E503.3070404@codeaurora.org> References: <1466812008-26686-1-git-send-email-timur@codeaurora.org> <4312386.60Y44nCzSI@wuerfel> <5773DC52.4010703@codeaurora.org> <5679359.84lXZytcOR@wuerfel> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5679359.84lXZytcOR@wuerfel> Sender: netdev-owner@vger.kernel.org To: Arnd Bergmann Cc: netdev@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-msm@vger.kernel.org, sdharia@codeaurora.org, shankerd@codeaurora.org, vikrams@codeaurora.org, cov@codeaurora.org, gavidov@codeaurora.org, robh+dt@kernel.org, andrew@lunn.ch, bjorn.andersson@linaro.org, mlangsdo@redhat.com, jcm@redhat.com, agross@codeaurora.org, davem@davemloft.net, f.fainelli@gmail.com, catalin.marinas@arm.com List-Id: devicetree@vger.kernel.org Arnd Bergmann wrote: > That's also not how it works: each device starts out with a 32-bit mask, > because that's what historically all PCI devices can do. If a device > is 64-bit DMA capable, it can extend the mask by passing DMA_BIT_MASK(64) > (or whatever it can support), and the platform code checks if that's > possible. So if it's not possible, then dma_set_mask returns an error, and the driver should try a smaller mask? Doesn't that mean that every driver for a 64-bit device should do this: for (i = 64; i >=32; i--) { ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(i)); if (!ret) break; } if (ret) return ret; Sure, this is overkill, but it seems to me that the driver does not really know what mask is actually valid, so it has to find the largest mask that works. -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation.