linux-kernel - Re: [PATCHv2 2/2] usb: pci-quirks: register USB mux found on Cherrytrail SOC

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Date:	Thu, 3 Dec 2015 22:01:39 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.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>,
	Felipe Balbi <balbi@...com>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 2/2] usb: pci-quirks: register USB mux found on
 Cherrytrail SOC

Hello.

On 12/03/2015 12:29 PM, Heikki Krogerus wrote:

> 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.

    Hm, I had somewhat identical case on the Renesas SoC: the 2 channel mux 
was mapped to the USB device PHY register space, so I chose to implement a PHY 
driver, not extcon...
    I don't quite understand how mux maps to the extcon core -- doesn't it 
provide support only the input signals?

> 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 | 26 +++++++++++++++++++++++++-
>   1 file changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci-quirks.c
> index 26cb8c8..ee875e1 100644
> --- a/drivers/usb/host/pci-quirks.c
> +++ b/drivers/usb/host/pci-quirks.c
[...]
> @@ -1022,9 +1023,32 @@ 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
> +		if (xhci_find_next_ext_cap(base, 0, XHCI_INTEL_VENDOR_CAPS)) {
> +			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)

    I think you can drop IS_ERR() check here...

> +				dev_dbg(&pdev->dev, "USB mux not supported\n");
> +			else if (IS_ERR(mux))
> +				dev_err(&pdev->dev, "failed to register mux\n");
> +		}
> +	}
> +
>   	op_reg_base = base + XHCI_HC_LENGTH(readl(base));
>
>   	/* Wait for the host controller to be ready before writing any

MBR, Sergei

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