Re: [PATCH] usb: dwc3: host: inherit dma configuration from parent dev

Peter Chen
2016-09-06T06:35:42Z

On Mon, Sep 05, 2016 at 05:39:27PM +0200, Arnd Bergmann wrote:
> On Friday, September 2, 2016 5:16:31 PM CEST Leo Li wrote:
> >
> > Can we use the firmware or bootloader information to provide the
> > default dma-mapping attributes for devices that doesn't have an
> > of_node pointer or ACPI data? This will at least restore what we had
> > previously provided . I'm concerned that changing all the drivers
> > that are creating child device will be a big effort. Like I mentioned
> > in another thread, there are many instances of platform_device_add()
> > under the drivers/ directory.
>
> Fortunately, there are not too many drivers that call platform_device_add
> *and* try to set up a dma mask for the child device:
>
> git grep -wl dma_mask drivers | xargs grep -wl 'platform_device_\(add\|register\)'
>
> drivers/base/platform.c
> drivers/bcma/main.c
> drivers/eisa/virtual_root.c
> drivers/mfd/mfd-core.c
> drivers/mfd/omap-usb-host.c
> drivers/misc/mic/card/mic_x100.c
> drivers/platform/goldfish/pdev_bus.c
> drivers/ssb/main.c
> drivers/usb/chipidea/core.c
> drivers/usb/dwc3/dwc3-exynos.c
> drivers/usb/dwc3/host.c
> drivers/usb/gadget/udc/bdc/bdc_pci.c
> drivers/usb/host/bcma-hcd.c
> drivers/usb/host/fsl-mph-dr-of.c
> drivers/usb/host/ssb-hcd.c
> drivers/usb/misc/ftdi-elan.c
> drivers/usb/musb/blackfin.c
> drivers/usb/musb/musb_dsps.c
> drivers/usb/musb/omap2430.c
> drivers/usb/musb/ux500.c
>
> Most of these are probably never used with any nonstandard
> DMA settings (IOMMU, cache coherency, offset, ...).
>
> One thing we could possibly do is to go through these and
> replace the hardcoded dma mask setup with of_dma_configure()
> in all cases in which we actually use DT for probing, which
> should cover the interesting cases.
>

One case I am going to work is to let USB chipidea driver support iommu,
the chipidea core device is no of_node, and created by
platform_add_device on the runtime. Using of_dma_configure with parent
of_node is a solution from my point, like [1].

https://lkml.org/lkml/2016/2/22/7

--

Best Regards,
Peter Chen