Hi Andy, On 24.10.2016 15:14, Andy Shevchenko wrote: > On Mon, 2016-10-24 at 14:34 +0200, Stefan Roese wrote: >> Hi! >> >> I'm currently trying to xfer data from system memory to a PCI >> device (FPGA) via DMA MEMCPY on a BayTrail based platform similar >> to the MinnowboardMax. For this I thought that I could use the >> integrated Synopsis DW DMA controller(s). My first tests show >> that the memory behind the PCI device is not updated with the >> DMA data though (no error message from the DMA driver though). >> I'm wondering now, if those 2 DMA controllers can be used for >> such generic PCI transfers. Or if they can only be used to >> transfer to the I2C / SPI / UART devices instead. >> >> Any infos / links on this would be very helpful. > > You can do memory-to-memory transfers, Good. > but not device-to-memory or > memory-to-device except mentioned ones because they are using request > lines wired inside SoC. > > Be careful BayTrail and Braswell has auto power gating for DMA and you > _have_to_ be sure that it's powered on before doing any access to it, > otherwise the bus and therefore OS will hang. It means any of the (ACPI) > device using those DMA shall be part of LPSS power domain. More > information is available in drivers/acpi_lpss.c. > > For PCI devices I have no idea how you can power DMA on except explicit > call of power_set_power_state() on certain struct pci_dev which you get > by BDF for the system. Thanks for the information. The DMA controller is powered and generates an interrupt: [ 30.308167] dw_dmac_pci 0000:00:1e.0: dw_dma_interrupt: status=0x1 [ 30.308179] dw_dmac_pci 0000:00:1e.0: dw_dma_tasklet: status_err=0 Still no data transferred to the PCI memory space (FPGA). The parameters passed to dwc_prep_dma_memcpy() seem to okay at first glance. I'll debug a bit to see, if I find a problem here. One related question: Do you know if and how the memory-to-memory transfer has been tested lately on such x86 platforms? Thanks, Stefan -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
