Hi,

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

Hi,

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

Hi,

On Thursday 06 March 2014 02:22 PM, Anton Tikhomirov wrote:

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Hello,

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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:

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Hi Kamil,

...

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+| 3. Supporting SoCs
++--------------------
+
+To support a new SoC a new file should be added to the

drivers/phy

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+directory. Each SoC's configuration is stored in an instance of

the

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+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.

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+};
+

...

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diff --git a/drivers/phy/phy-samsung-usb2.c b/drivers/phy/phy-

samsung-

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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@samsung.com>
+ *
+ * This program is free software; you can redistribute it

and/or

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modify
+ * it under the terms of the GNU General Public License version

2

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as

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+ * 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);

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+	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

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it's fine to have clk_prepare_enable() here.

If we rely totally on generic PHY functions such as phy_power_on()
and friends, why do we need to use locking in callbacks at all.

Didn't get you.. We don't want to invoke power_on when init is

getting

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executed or you don't want power on or power off to get executed
simultaneously right? So we need to protect it.

I mean callbacks such as samsung_usb2_phy_power_on() which uses
spin_lock.
It's already protected by mutex in phy_power_on().

Well... phy_power_on() uses mutex to protect power_on() callback.
power_on() is samsung_usb2_phy_power_on() in our case.
samsung_usb2_phy_power_on() uses spinlock.
My question is why do we need to use spinlock _inside_ callback
if it is already protected by mutex.