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

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Date:	Thu, 06 Mar 2014 11:24:44 +0100
From:	Kamil Debski <k.debski@...sung.com>
To:	'Anton Tikhomirov' <av.tikhomirov@...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, kishon@...com,
	Tomasz Figa <t.figa@...sung.com>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Marek Szyprowski <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

Hi Anton, Kishon,

> From: Anton Tikhomirov [mailto:av.tikhomirov@...sung.com]
> Sent: Thursday, March 06, 2014 9:26 AM
> 
> 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.

Thank you for spotting this.

Kishon: I am sorry that this omission was made. I am happy to send an
updated patchset. However, I want to give some time for any additional
comments. Do you think that we have for this? Is today evening ok with you?
> 
> > +};
> > +
> 
> ...
> 
> > 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).

>From the onward discussion between you and Kishon, I draw the conclusion
that this change is not necessary. Right?

> 
> > +	if (ret)
> > +		goto err_main_clk;
> > +	ret = clk_prepare_enable(drv->ref_clk);
> > +	if (ret)
> > +		goto err_instance_clk;
> > +	if (inst->cfg->power_on) {
> > +		spin_lock(&drv->lock);
> > +		ret = inst->cfg->power_on(inst);
> > +		spin_unlock(&drv->lock);
> > +	}
> > +
> > +	return 0;
> 
> Thank you

Best wishes,
-- 
Kamil Debski
Samsung R&D Institute Poland


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