linux-kernel - Re: [PATCH 1/2] extcon: add driver for Intel USB mux

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Message-ID: <87r3j5zz51.fsf@saruman.tx.rr.com>
Date:	Tue, 1 Dec 2015 14:34:34 -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 1/2] extcon: add driver for Intel USB mux


Hi,

Heikki Krogerus <heikki.krogerus@...ux.intel.com> writes:
> Several Intel PCHs and SOCs have an internal mux that is
> used to share one USB port between USB Device Controller and
> xHCI. The mux is normally handled by System FW/BIOS, but not
> always. For those platforms where the FW does not take care
> of the mux, this driver is needed.

except that this is not exactly a driver. Note that it lacks a
module_init() of its own.

> diff --git a/drivers/extcon/extcon-intel-usb.c b/drivers/extcon/extcon-intel-usb.c
> new file mode 100644
> index 0000000..5534781
> --- /dev/null
> +++ b/drivers/extcon/extcon-intel-usb.c
> @@ -0,0 +1,112 @@
> +/**
> + * extcon-intel-usb.c - Driver for Intel USB mux
> + *
> + * Copyright (C) 2015 Intel Corporation
> + * Author: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/slab.h>
> +#include <linux/extcon.h>
> +
> +#include <linux/extcon/intel_usb_mux.h>
> +
> +#define INTEL_MUX_CFG0		0x00
> +#define INTEL_MUX_CFG1		0x04
> +
> +#define CFG0_SW_DRD_MODE_MASK	0x3
> +#define CFG0_SW_DRD_DYN		0
> +#define CFG0_SW_DRD_STATIC_HOST	1
> +#define CFG0_SW_DRD_STATIC_DEV	2
> +#define CFG0_SW_SYNC_SS_AND_HS	BIT(2)
> +#define CFG0_SW_SWITCH_EN	BIT(16)
> +#define CFG0_SW_IDPIN		BIT(20)
> +#define CFG0_SW_IDPIN_EN	BIT(21)
> +#define CFG0_SW_VBUS_VALID	BIT(24)
> +
> +#define CFG1_MODE		BIT(29)
> +
> +struct intel_usb_mux {
> +	struct notifier_block nb;
> +	struct extcon_dev edev;
> +	void __iomem *regs;
> +	u32 cfg0_ctx;
> +};
> +
> +static const int intel_mux_cable[] = {
> +	EXTCON_USB_HOST,
> +	EXTCON_NONE,
> +};
> +
> +static int intel_usb_mux_notifier(struct notifier_block *nb,
> +				  unsigned long old, void *ptr)
> +{
> +	struct intel_usb_mux *mux = container_of(nb, struct intel_usb_mux, nb);
> +	u32 val;
> +
> +	if (mux->edev.state)
> +		val = CFG0_SW_IDPIN_EN | CFG0_SW_DRD_STATIC_HOST;
> +	else
> +		val = CFG0_SW_IDPIN_EN | CFG0_SW_IDPIN | CFG0_SW_VBUS_VALID |
> +		      CFG0_SW_DRD_STATIC_DEV;
> +
> +	writel(val, mux->regs);
> +	return NOTIFY_OK;
> +}
> +
> +struct intel_usb_mux *intel_usb_mux_register(struct device *dev,
> +					     struct resource *r)
> +{
> +	struct intel_usb_mux *mux;
> +	int ret;
> +
> +	mux = kzalloc(sizeof(*mux), GFP_KERNEL);
> +	if (!mux)
> +		return ERR_PTR(-ENOMEM);
> +
> +	mux->regs = ioremap_nocache(r->start, resource_size(r));
> +	if (!mux->regs) {
> +		kfree(mux);
> +		return ERR_PTR(-ENOMEM);
> +	}
> +
> +	mux->cfg0_ctx = readl(mux->regs + INTEL_MUX_CFG0);
> +
> +	mux->edev.dev.parent = dev;
> +	mux->edev.supported_cable = intel_mux_cable;
> +
> +	ret = extcon_dev_register(&mux->edev);
> +	if (ret)
> +		goto err;
> +
> +	mux->edev.name = "intel_usb_mux";
> +	mux->edev.state = !!(readl(mux->regs + INTEL_MUX_CFG1) & CFG1_MODE);
> +
> +	/* An external source needs to tell us what to do */
> +	mux->nb.notifier_call = intel_usb_mux_notifier;
> +	ret = extcon_register_notifier(&mux->edev, EXTCON_USB_HOST, &mux->nb);
> +	if (ret) {
> +		dev_err(&mux->edev.dev, "failed to register notifier\n");
> +		extcon_dev_unregister(&mux->edev);
> +		goto err;
> +	}
> +	return mux;
> +err:
> +	iounmap(mux->regs);
> +	kfree(mux);
> +	return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL_GPL(intel_usb_mux_register);
> +
> +void intel_usb_mux_unregister(struct intel_usb_mux *mux)
> +{
> +	extcon_unregister_notifier(&mux->edev, EXTCON_USB_HOST, &mux->nb);
> +	extcon_dev_unregister(&mux->edev);
> +	writel(mux->cfg0_ctx, mux->regs + INTEL_MUX_CFG0);
> +	iounmap(mux->regs);
> +	kfree(mux);
> +}
> +EXPORT_SYMBOL_GPL(intel_usb_mux_unregister);

so who's gonna call these two functions ? IMO, this looks like a recipe
for randbuild breakage.

-- 
balbi

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