linux-kernel - Re: [PATCH 2/4] usb: host: xhci-plat: Add support to get PHYs

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Date:	Mon, 9 Jun 2014 13:22:14 -0700
From:	Julius Werner <jwerner@...omium.org>
To:	Vivek Gautam <gautam.vivek@...sung.com>
Cc:	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	kishon <kishon@...com>, Mathias Nyman <mathias.nyman@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Julius Werner <jwerner@...omium.org>
Subject: Re: [PATCH 2/4] usb: host: xhci-plat: Add support to get PHYs

> diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
> index 9ffecd5..453d89e 100644
> --- a/drivers/usb/host/xhci.h
> +++ b/drivers/usb/host/xhci.h
> @@ -1582,6 +1582,9 @@ struct xhci_hcd {
>         u32                     port_status_u0;
>  /* Compliance Mode Timer Triggered every 2 seconds */
>  #define COMP_MODE_RCVRY_MSECS 2000
> +       /* phys for the controller */
> +       struct phy              *phy2_gen;
> +       struct phy              *phy3_gen;
>  };

I don't think adding new variables here and restricting most of this
logic to xhci-plat.c (in the next patch) is the best way to do it.
There's no conceptual reason why other host controllers (e.g. xhci-pci
or even EHCI) could not have a similar need to tune their PHY after
reset. PHYs are universal to all host controllers.

There is already a 'phy' member in struct usb_hcd which I think is
mostly unused right now. I think it would be much less
confusing/redundant to reuse that member for this purpose (you could
still set it up from xhci_plat_probe(), and then call it from
hcd_bus_resume() or something like that). Since XHCI host controllers
already conveniently have two struct usb_hcd (one for 2.0 and one for
3.0), you can cleanly store references to your two PHYs in there.
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