Messages in this thread | | | Subject | Re: [PATCH] spi/pxa2xx-pci: Enable DMA binding through device name | From | Andy Shevchenko <> | Date | Mon, 28 Jul 2014 14:06:20 +0300 |
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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 <andriy.shevchenko@intel.com> Intel Finland Oy
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