From mboxrd@z Thu Jan 1 00:00:00 1970 From: andriy.shevchenko@linux.intel.com (Andy Shevchenko) Date: Mon, 28 Jul 2014 14:06:20 +0300 Subject: [PATCH] spi/pxa2xx-pci: Enable DMA binding through device name In-Reply-To: <5237362.DJsH7MtqlU@wuerfel> References: <1406196111-22861-1-git-send-email-hock.leong.kweh@intel.com> <5426556.OzZIXLrofJ@wuerfel> <1406285147.8530.13.camel@smile.fi.intel.com> <5237362.DJsH7MtqlU@wuerfel> Message-ID: <1406545580.8530.28.camel@smile.fi.intel.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, 2014-07-25 at 17:55 +0200, Arnd Bergmann wrote: > On Friday 25 July 2014 13:45:47 Andy Shevchenko wrote: > > On Fri, 2014-07-25 at 12:19 +0200, Arnd Bergmann wrote: > > > On Friday 25 July 2014 12:55:59 Mika Westerberg wrote: > > > > On Fri, Jul 25, 2014 at 12:07:14PM +0300, Mika Westerberg wrote: > > > > > On Fri, Jul 25, 2014 at 10:38:36AM +0200, Arnd Bergmann wrote: > > > > > > On Friday 25 July 2014 11:22:49 Mika Westerberg wrote: > > > > [] > > > > > > Something like this? > > > > Arnd, this dependency to certain DMA driver looks really bad. > > > > If we go that way, can we split that part to [another] module and make > > it dependent to DW_DMAC? > > I don't see what you gain from that. The PCI ID will tell you which DMA > engine is being used. The driver already hardcodes a slave_id based on > the PCI ID today, and the "...and the..."? > > > Or shall we introduce a dmaengine type field in the platform data and > > dynamically choose proper filter-whatever-function to get the channel? > > We already have an interface for this, in the form of > dma_request_slave_channel(), which takes a string identifier that > is used to look up all that information in either device tree or > ACPI. It wouldn't be unreasonable to add a third path in there > to handle hardcoded platform devices, but that's a lot of work. > Note that you still need to encode a reference to the dma engine > in some way to do this right. The current code (with or without Mika's > patch) will break as soon as you have multiple DMA engine devices. What about to keep PCI case still valid? We can pass struct pci_dev (or actual struct device) of DMA controller to filter proper device. > The current plan I think is to convert all platforms to use DT > or ACPI so they get the right data from tables passed by the > platform. Good to know the road map. [] > > > What I think you got wrong here (by following my bad advice) is the master > > > number. Looking at the code for dw_dma, I think src_master needs to be '1' > > > for your driver. > > > > On some SoCs we have up to 4 masters. It's blurry for me how the SPI > > should choose those masters. Currently it works fine, but I suspect > > there are [might be] performance issues. > > I think it works because the dw-dma defaults to the values used by > the specific implementation in your hardware. > > What about AVR32 case? We have to fix drivers as well there. > which ones? arch/avr32/mach-at32ap/at32ap700x.c:1332:at32_add_device_mci It seems opaque for me if it's used anywhere. -- Andy Shevchenko Intel Finland Oy