From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH v6 07/12] usb: chipidea: add a usb2 driver for ci13xxx Date: Fri, 26 Sep 2014 09:01:49 +0200 Message-ID: <202048167.dt5r3yRThs@wuerfel> References: <1411468088-5702-1-git-send-email-antoine.tenart@free-electrons.com> <3696520.MDUrkdjfGZ@wuerfel> <20140926002339.GB3026@peterchendt> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <20140926002339.GB3026@peterchendt> Sender: linux-kernel-owner@vger.kernel.org To: Peter Chen Cc: linux-arm-kernel@lists.infradead.org, Antoine Tenart , thomas.petazzoni@free-electrons.com, zmxu@marvell.com, devicetree@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, balbi@ti.com, alexandre.belloni@free-electrons.com, p.zabel@pengutronix.de, jszhang@marvell.com, sebastian.hesselbarth@gmail.com List-Id: devicetree@vger.kernel.org On Friday 26 September 2014 08:23:40 Peter Chen wrote: > In current chipidea structure, the parent (glue layer) driver will not be > used for dma, udc/host driver uses dma mask from child (core layer), at core > layer we will do: > > > pdev->dev.dma_mask = dev->dma_mask; /* this device is parent */ > dma_set_coherent_mask(&pdev->dev, dev->coherent_dma_mask); > > Would you suggestion us a suitable way? Or it is ok we use just Antoine's way that > call dma_coerce_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32)) at parent > driver no matter dt or non-dt? Thanks. dma_coerce_mask_and_coherent is not ok, it will force a dma mask that is unrelated to the actual requirements of the hardware. I think the best way would be to never use the child device pointer for DMA operations, just use a pointer to the parent device and make the child dev->dma_mask pointer NULL to ensure all DMA operations fail. Arnd