From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH v4 1/5] drm/rockchip: Add basic drm driver Date: Mon, 22 Sep 2014 17:54:42 +0200 Message-ID: <3102396.6rAQmqkXXM@wuerfel> References: <1411382820-1615-1-git-send-email-mark.yao@rock-chips.com> <3036415.u40f3Xnhod@wuerfel> <20140922171506.31d59a76@bbrezillon> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <20140922171506.31d59a76@bbrezillon> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Boris BREZILLON Cc: Mark yao , heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org, David Airlie , Rob Clark , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Randy Dunlap , Grant Likely , Greg Kroah-Hartman , John Stultz , Rom Lemarchand , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-rockchip-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org, marcheu-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org, dbehr-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org, olof-nZhT3qVonbNeoWH0uzbU5w@public.gmane.org, djkurtz-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org, xjq-TNX95d0MmH7DzftRWevZcw@public.gmane.org, kfx-TNX95d0MmH7DzftRWevZcw@public.gmane.org, cym-TNX95d0MmH7DzftRWevZcw@public.gmane.org, cf-TNX95d0MmH7DzftRWevZcw@public.gmane.org, zyw@rock- List-Id: linux-api@vger.kernel.org On Monday 22 September 2014 17:15:06 Boris BREZILLON wrote: > > > + > > > + /* TODO(djkurtz): fetch the mapping start/size from somewhere */ > > > + mapping = arm_iommu_create_mapping(&platform_bus_type, 0x10000000, > > > + SZ_1G); > > > + if (IS_ERR(mapping)) { > > > + ret = PTR_ERR(mapping); > > > + goto err_config_cleanup; > > > + } > > > + > > > + dma_set_coherent_mask(dev, DMA_BIT_MASK(32)); > > > > This is the default coherent mask. If you call this function, you > > should normally check the return value, or call dma_set_mask first, > > which you apparently don't do here, and in another place in this > > patch. > > By "This is the default mask" do you mean it shouldn't be called at > all ? Cause I ran into some trouble when not calling this in my > atmel-hlcdc driver. We used to get this wrong in the of_platform code, but it should work now. > Actually, in my case the platform device is created by the MFD core > which seems to let the coherent_dma_mask uninitialized. That may well be different, but it seems like a good idea to allow the MFD core to set this up as well. In general, we expect that devices that are capable of doing DMA start with a 32-bit mask for both dma_mask and dma_coherent_mask, and a driver that requires a smaller masks or wants a larger mask has to call the appropriate interface to set these, and check the return value. Arnd -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html