linux-kernel - Re: [PATCH 2/2] usb: pci-quirks: register USB mux found on Cherrytrail SOC

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Date:	Tue, 1 Dec 2015 14:38:38 -0600
From:	Felipe Balbi <balbi@...com>
To:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	MyungJoo Ham <myungjoo.ham@...sung.com>,
	David Cohen <david.a.cohen@...ux.intel.com>,
	Lu Baolu <baolu.lu@...ux.intel.com>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] usb: pci-quirks: register USB mux found on Cherrytrail SOC


Hi,

Heikki Krogerus <heikki.krogerus@...ux.intel.com> writes:
> Intel Braswell/Cherrytrail has an internal mux that shares
> one USB port between USB Device Controller and xHCI. The
> same mux is found on several SOCs from Intel, but only on
> a few Cherrytrail based platforms the OS is expected to
> configure it. Normally BIOS takes care of it.
>
> The driver for the mux is an "extcon" driver. With this we
> only register the mux if it's detected.
>
> Suggested-by: Lu Baolu <baolu.lu@...ux.intel.com>
> Signed-off-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> ---
>  drivers/usb/host/pci-quirks.c | 30 +++++++++++++++++++++++++++++-
>  1 file changed, 29 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci-quirks.c
> index f940056..4e3016a 100644
> --- a/drivers/usb/host/pci-quirks.c
> +++ b/drivers/usb/host/pci-quirks.c
> @@ -16,6 +16,7 @@
>  #include <linux/export.h>
>  #include <linux/acpi.h>
>  #include <linux/dmi.h>
> +#include <linux/extcon/intel_usb_mux.h>
>  #include "pci-quirks.h"
>  #include "xhci-ext-caps.h"
>  
> @@ -1029,9 +1030,36 @@ static void quirk_usb_handoff_xhci(struct pci_dev *pdev)
>  	writel(val, base + ext_cap_offset + XHCI_LEGACY_CONTROL_OFFSET);
>  
>  hc_init:
> -	if (pdev->vendor == PCI_VENDOR_ID_INTEL)
> +	if (pdev->vendor == PCI_VENDOR_ID_INTEL) {
>  		usb_enable_intel_xhci_ports(pdev);
>  
> +		/*
> +		 * Initialize the internal mux that shares a port between USB
> +		 * Device Controller and xHCI on platforms that have it.
> +		 */
> +#define XHCI_INTEL_VENDOR_CAPS 192
> +#define XHCI_INTEL_USB_MUX_OFFSET 0x80d8
> +		ext_cap_offset = xhci_find_next_cap_offset(base,
> +							XHCI_HCC_PARAMS_OFFSET);
> +		ext_cap_offset = xhci_find_ext_cap_by_id(base, ext_cap_offset,
> +							XHCI_INTEL_VENDOR_CAPS);
> +		if (ext_cap_offset) {
> +			struct intel_usb_mux *mux;
> +			struct resource r;
> +
> +			r.start = pci_resource_start(pdev, 0) +
> +					XHCI_INTEL_USB_MUX_OFFSET;
> +			r.end   = r.start + 8;
> +			r.flags = IORESOURCE_MEM;
> +
> +			mux = intel_usb_mux_register(&pdev->dev, &r);
> +			if (IS_ERR(mux) && PTR_ERR(mux) == -ENOTSUPP)
> +				dev_dbg(&pdev->dev, "USB mux not supported\n");
> +			else if (IS_ERR(mux))
> +				dev_err(&pdev->dev, "failed to register mux\n");

IMHO, this should be creating a child device instead of calling
intel_usb_mux_register() directly. That way, your mux driver could
actually _be_ a driver. Seems like all you need to do from this point is
a register a simple platform_device which is a child of xhci, see
platform_device_register_simple() for how to do this.

Or rather, platform_device_register_rsndata() passing xhci's device
pointer as parent.

-- 
balbi

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