linux-kernel - Re: [RFC PATCH] USB: host: ehci-atmel: Allow enabling HSIC on SAMA5D2

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Date:   Tue, 24 Aug 2021 08:45:25 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Alexander Dahl <ada@...rsis.com>
Cc:     linux-usb@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Alan Stern <stern@...land.harvard.edu>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] USB: host: ehci-atmel: Allow enabling HSIC on SAMA5D2

On Tue, Aug 24, 2021 at 08:37:02AM +0200, Alexander Dahl wrote:
> Unlike other SoC series featuring the 'atmel,at91sam9g45-ehci' USB EHCI
> controller, which have embedded USB high-speed transceivers for each
> port, the third port on the SAMA5D2 series is HSIC only.  That HSIC
> interface is not enabled after a power-on reset, but can be enabled by
> setting a flag in a vendor specific EHCI register.
> 
> The register offsets added to the new header file were compared with
> those for the SAM9G45, SAM9X25, SAMA5D3, SAMA5D4, and SAM9X60 series and
> there are no differences in the offsets or contents of those registers.
> Which of those additional vendor specific registers are supported,
> differs by SoC family.  So while the HSIC enable feature is currently
> only present for SAMA5D2, it probably does not hurt to set it on the
> other families, hence no additional check for SoC family here.
> 
> Tested on a custom board featuring a SAMA5D27C-D5M SiP connected to an
> USB3503 hub with an upstream HSIC interface.
> 
> Link: https://community.atmel.com/forum/sama5d2-using-hsic-under-linux
> Signed-off-by: Alexander Dahl <ada@...rsis.com>
> ---
> 
> Notes:
>     - for introducing new dt binding, would be nice to convert old one
>       first, probably needs split up and multiple iteration review?
>     - name of that new dt property?
>     - register definitions put to a separate file, like
>       'drivers/usb/host/ehci-fsl.h'
>     - unsure where exactly in the probe process that register write should
>       happen, datasheet gives no hint
>     - should suspend/resume be considered?
> 
>  drivers/usb/host/ehci-atmel.c | 17 +++++++++++++++++
>  drivers/usb/host/ehci-atmel.h | 19 +++++++++++++++++++

No need for a new .h file that is only used in a single .c file.  Just
put those few lines in the .c file please.

thanks,

greg k-h