linux-kernel - Re: [PATCH v9 3/4] phy: Add new Exynos USB 2.0 PHY driver

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Date:	Thu, 6 Mar 2014 14:00:24 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	Anton Tikhomirov <av.tikhomirov@...sung.com>,
	"'Kamil Debski'" <k.debski@...sung.com>,
	<linux-kernel@...r.kernel.org>,
	<linux-samsung-soc@...r.kernel.org>, <linux-usb@...r.kernel.org>,
	<devicetree@...r.kernel.org>
CC:	<kyungmin.park@...sung.com>, <t.figa@...sung.com>,
	<s.nawrocki@...sung.com>, <m.szyprowski@...sung.com>,
	<gautam.vivek@...sung.com>, <mat.krawczuk@...il.com>,
	<yulgon.kim@...sung.com>, <p.paneri@...sung.com>,
	<jg1.han@...sung.com>, <galak@...eaurora.org>,
	<matt.porter@...aro.org>, <tjakobi@...h.uni-bielefeld.de>,
	<stern@...land.harvard.edu>, <sander@...ilis.net>
Subject: Re: [PATCH v9 3/4] phy: Add new Exynos USB 2.0 PHY driver



On Thursday 06 March 2014 01:56 PM, Anton Tikhomirov wrote:
> Hi Kamil,
>
> ...
>
>> +| 3. Supporting SoCs
>> ++--------------------
>> +
>> +To support a new SoC a new file should be added to the drivers/phy
>> +directory. Each SoC's configuration is stored in an instance of the
>> +struct samsung_usb2_phy_config.
>> +
>> +struct samsung_usb2_phy_config {
>> +	const struct samsung_usb2_common_phy *phys;
>> +	unsigned int num_phys;
>> +	bool has_mode_switch;
>
> You missed rate_to_clk here.
>
>> +};
>> +
>
> ...
>
>> diff --git a/drivers/phy/phy-samsung-usb2.c b/drivers/phy/phy-samsung-
>> usb2.c
>> new file mode 100644
>> index 0000000..c3b7719
>> --- /dev/null
>> +++ b/drivers/phy/phy-samsung-usb2.c
>> @@ -0,0 +1,222 @@
>> +/*
>> + * Samsung SoC USB 1.1/2.0 PHY driver
>> + *
>> + * Copyright (C) 2013 Samsung Electronics Co., Ltd.
>> + * Author: Kamil Debski <k.debski@...sung.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/clk.h>
>> +#include <linux/mfd/syscon.h>
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/of_address.h>
>> +#include <linux/phy/phy.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/spinlock.h>
>> +#include "phy-samsung-usb2.h"
>> +
>> +static int samsung_usb2_phy_power_on(struct phy *phy)
>> +{
>> +	struct samsung_usb2_phy_instance *inst = phy_get_drvdata(phy);
>> +	struct samsung_usb2_phy_driver *drv = inst->drv;
>> +	int ret;
>> +
>> +	dev_dbg(drv->dev, "Request to power_on \"%s\" usb phy\n",
>> +		inst->cfg->label);
>> +	ret = clk_prepare_enable(drv->clk);
>
> clk_prepare_enable() can sleep, and therefore doesn't allow
> samusng_usb2_phy_power_on() to be used in atomic context
> (e.g. inside spin_lock-ed area), what sometimes may be desirable.
> What about to prepare clock in probe, and just enable it here
> (note: clk_enable() doesn't sleep).

The PHY power-on callback is anyway called with mutex held, so I guess 
it's fine to have clk_prepare_enable() here.

Thanks
Kishon
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