Re: [RFC PATCH] USB: host: ehci-atmel: Allow enabling HSIC on SAMA5D2 - Greg Kroah-Hartman

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Alexander Dahl <ada@thorsis.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
	Ludovic Desroches <ludovic.desroches@microchip.com>,
	Alan Stern <stern@rowland.harvard.edu>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH] USB: host: ehci-atmel: Allow enabling HSIC on SAMA5D2
Date: Tue, 24 Aug 2021 08:45:25 +0200	[thread overview]
Message-ID: <YSSVhblgt/45TvzF@kroah.com> (raw)
In-Reply-To: <20210824063702.24586-1-ada@thorsis.com>

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@thorsis.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

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