Messages in this thread | | | Date | Mon, 23 Aug 2021 10:00:52 -0400 | From | Alan Stern <> | Subject | Re: Enable HSIC Host Port on Atmel/Microchip SAMA5D2 |
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On Mon, Aug 23, 2021 at 11:24:35AM +0200, Alexander Dahl wrote: > Hello, > > for a new embedded board featuring a Microchip SAMA5D2 SoC (64 MiB SiP variant > SAMA5D27C-D5M) we connected the third USB host port (HSIC only) with an > USB3503 hub chip. This doesn't work out of the box with the Linux kernel > currently, because neither the SoC nor the kernel does enable the HSIC > interface by default. > > That SoC has three USB host ports, from the SAMA5D2 Series Datasheet [1] I > learned there's a flag in an EHCI register, which has to be set to enable the > HSIC interface on port C, the third port. (Section "41.7.14 EHCI: REG08 - HSIC > Enable/Disable" of the datasheet.) I suppose that register is vendor specific. > The register definitions in '/include/linux/usb/ehci_def.h' do not contain > that register. > > Where would I add that register definition and set that flag in the kernel > then? I suppose in the vendor specific ehci driver? > That would be 'drivers/usb/host/ehci-atmel.c' right?
That is where you would set the flag. You might want to put the register definition in ehci_def.h, with the other definitions.
> Since that feature is optional (other boards don't need to turn on hsic on > that port), some driver specific new device tree binding would be necessary, > right? I suppose that would have to be documented in 'Documentation/ > devicetree/bindings/usb/atmel-usb.txt' right? (Or that would have to be > converted to yaml first?)
Yes, it would have to go into the device tree data somehow. I don't know the best way to do this; people who know more about DT may be able to tell you.
> Is this the right track? If yes, I'm going to develop patches for this. > Otherwise any hint into the right direction are highly appreciated.
Yes, this is the right approach.
Alan Stern
> FWIW, I'm not the first one struggling [2] with this problem. ;-) > > Greets > Alex > > [1] https://www.microchip.com/en-us/product/ATSAMA5D27C-D5M#document-table > [2] https://community.atmel.com/forum/sama5d2-using-hsic-under-linux
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