Date:	Mon, 17 Sep 2012 11:33:12 +0200
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	"ABRAHAM, KISHON VIJAY" <kishon@...com>
CC:	balbi@...com, arnd@...db.de, gregkh@...uxfoundation.org,
	linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org, richard.zhao@...escale.com,
	B29397@...escale.com, alexander.shishkin@...ux.intel.com,
	marex@...x.de
Subject: Re: [RFC PATCH] drivers: phy: add generic PHY framework

On 09/14/2012 03:06 PM, ABRAHAM, KISHON VIJAY wrote:

[...]

>>> diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c
>>> new file mode 100644
>>> index 0000000..c55446a
>>> --- /dev/null
>>> +++ b/drivers/phy/phy-core.c
>>> @@ -0,0 +1,437 @@
>>> +/*
>>> + * phy-core.c  --  Generic Phy framework.
>>> + *
>>> + * Copyright (C) 2012 Texas Instruments
>>> + *
>>> + * Author: Kishon Vijay Abraham I <kishon@...com>
>>> + *
>>> + * This program is free software; you can redistribute  it and/or modify it
>>> + * under  the terms of  the GNU General  Public License as published by the
>>> + * Free Software Foundation;  either version 2 of the  License, or (at your
>>> + * option) any later version.
>>> + *
>>> + * This program is distributed in the hope that it will be useful,
>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>> + * GNU General Public License for more details.
>>> + *
>>> + * You should have received a copy of the GNU General Public License
>>> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
>>> + */
>>> +
>>> +#include <linux/kernel.h>
>>> +#include <linux/export.h>
>>> +#include <linux/module.h>
>>> +#include <linux/err.h>
>>> +#include <linux/device.h>
>>> +#include <linux/slab.h>
>>> +#include <linux/of.h>
>>> +#include <linux/phy/phy.h>
>>> +
>>> +static struct class *phy_class;
>>> +static LIST_HEAD(phy_list);
>>> +static DEFINE_MUTEX(phy_list_mutex);
>>> +static LIST_HEAD(phy_bind_list);
>>> +
>>> +static void devm_phy_release(struct device *dev, void *res)
>>> +{
>>> +     struct phy *phy = *(struct phy **)res;
>>
>> What about adding a struct phy_res, doing so,m you don't need these
>> casts, and it's easier to add more pointers if needed.
> 
> Wont we still need to do the cast since you get only a void pointer.
> Maybe I'm not getting you.

As "res" is a void pointer, no need to hast to to a "struct phy_res"
pointer, if you think that's unclean code, you can still cast it. But
IMHO the code is far more readable.

>>> +
>>> +     phy_put(phy);
>>> +}
>>> +
>>> +static int devm_phy_match(struct device *dev, void *res, void *match_data)
>>> +{
>>> +     return res == match_data;
>>> +}
>>> +
>>> +static struct phy *phy_lookup(struct device *dev, u8 index)
>>> +{
>>> +     struct phy_bind *phy_bind = NULL;
>>> +
>>> +     list_for_each_entry(phy_bind, &phy_bind_list, list) {
>>> +             if (!(strcmp(phy_bind->dev_name, dev_name(dev))) &&
>>> +                             phy_bind->index == index)
>>> +                     return phy_bind->phy;
>>> +     }
>>> +
>>> +     return ERR_PTR(-ENODEV);
>>> +}
>>> +
>>> +static struct phy *of_phy_lookup(struct device *dev, struct device_node *node)
>>> +{
>>> +     int index = 0;
>>> +     struct phy  *phy;
>>                   ^^
>>
>> Please remove that stray space.
> 
> Sure.
>>
>>> +     struct phy_bind *phy_map = NULL;
>>> +
>>> +     list_for_each_entry(phy_map, &phy_bind_list, list)
>>> +             if (!(strcmp(phy_map->dev_name, dev_name(dev))))
>>> +                     index++;
>>> +
>>> +     list_for_each_entry(phy, &phy_list, head) {
>>> +             if (node != phy->desc->of_node)
>>> +                     continue;
>>> +
>>> +             phy_map = phy_bind(dev_name(dev), index, dev_name(&phy->dev));
>>> +             if (!IS_ERR(phy_map)) {
>>> +                     phy_map->phy = phy;
>>> +                     phy_map->auto_bind = true;
>>> +             }
>>> +
>>> +             return phy;
>>> +     }
>>> +
>>> +     return ERR_PTR(-ENODEV);
>>> +}
>>> +
>>> +/**
>>> + * devm_phy_get - lookup and obtain a reference to a phy.
>>> + * @dev: device that requests this phy
>>> + * @index: the index of the phy
>>> + *
>>> + * Gets the phy using phy_get(), and associates a device with it using
>>> + * devres. On driver detach, release function is invoked on the devres data,
>>> + * then, devres data is freed.
>>> + */
>>> +struct phy *devm_phy_get(struct device *dev, u8 index)
>>> +{
>>> +     struct phy **ptr, *phy;
>>> +
>>> +     ptr = devres_alloc(devm_phy_release, sizeof(*ptr), GFP_KERNEL);
>>> +     if (!ptr)
>>> +             return NULL;
>>> +
>>> +     phy = phy_get(dev, index);
>>> +     if (!IS_ERR(phy)) {
>>> +             *ptr = phy;
>>> +             devres_add(dev, ptr);
>>> +     } else
>>> +             devres_free(ptr);
>>
>> nitpick: when when if has { }, else should have, too.
> 
> Sure.
>>
>>> +
>>> +     return phy;
>>> +}
>>> +EXPORT_SYMBOL_GPL(devm_phy_get);
>>> +
>>> +/**
>>> + * devm_phy_put - release the PHY
>>> + * @dev: device that wants to release this phy
>>> + * @phy: the phy returned by devm_phy_get()
>>> + *
>>> + * destroys the devres associated with this phy and invokes phy_put
>>> + * to release the phy.
>>> + */
>>> +void devm_phy_put(struct device *dev, struct phy *phy)
>>> +{
>>> +     int r;
>>> +
>>> +     r = devres_destroy(dev, devm_phy_release, devm_phy_match, phy);
>>> +     dev_WARN_ONCE(dev, r, "couldn't find PHY resource\n");
>>> +}
>>> +EXPORT_SYMBOL_GPL(devm_phy_put);
>>> +
>>> +/**
>>> + * devm_of_phy_get - lookup and obtain a reference to a phy by phandle
>>> + * @dev: device that requests this phy
>>> + * @phandle: name of the property holding the phy phandle value
>>> + *
>>> + * Returns the phy driver associated with the given phandle value,
>>> + * after getting a refcount to it or -ENODEV if there is no such phy.
>>> + * While at that, it also associates the device with the phy using devres.
>>> + * On driver detach, release function is invoked on the devres data,
>>> + * then, devres data is freed.
>>> + */
>>> +struct phy *devm_of_phy_get(struct device *dev, const char *phandle)
>>
>> We should discuss first how the DT binding for a phy should look like. I
>> don't like that you hardcode the index (in of_parse_phandle()) to "0".
>> Then we have the problem with USB2 and USB3 phys for the same usb device.
> 
> I think then we should modify this API to take *index* which should be
> used when we have a single controller using multiple phys. By that
> we'll make both dt and non-dt similar in that, both of them will take
> this index.

That would be a plus.

>>
>>> +{
>>> +     struct phy      *phy = NULL, **ptr;

nitpick: stray spaces

>>> +     struct device_node *node;
>>> +
>>> +     if (!dev->of_node) {
>>> +             dev_dbg(dev, "device does not have a device node entry\n");
>>> +             return ERR_PTR(-EINVAL);
>>> +     }
>>> +
>>> +     node = of_parse_phandle(dev->of_node, phandle, 0);

BTW: Is the node freed somewhere?

>>> +     if (!node) {
>>> +             dev_dbg(dev, "failed to get %s phandle in %s node\n", phandle,
>>> +                     dev->of_node->full_name);
>>> +             return ERR_PTR(-ENODEV);
>>> +     }
>>> +
>>> +     ptr = devres_alloc(devm_phy_release, sizeof(*ptr), GFP_KERNEL);
>>> +     if (!ptr) {
>>> +             dev_dbg(dev, "failed to allocate memory for devres\n");
>>> +             return ERR_PTR(-ENOMEM);
>>> +     }
>>> +
>>> +     mutex_lock(&phy_list_mutex);
>>> +
>>> +     phy = of_phy_lookup(dev, node);
>>> +     if (IS_ERR(phy) || !try_module_get(phy->dev.driver->owner)) {

Where's the corresponding module_put? You should add module_get to the
non dt function, too.

>>> +             devres_free(ptr);
>>> +             goto err0;
>>> +     }
>>
>> Please return -EPROBE_DEFER is the phy is not yet registered.
> 
> I really dont prefer to return -EPROBE_DEFER from the *framework*.
> IMHO, it's up-to the caller of this API to return *probe* errors.

If we leave it to the caller, you have to proper design your return
values. There is a difference betweeen:
a) the phandle + index point to a non existing device node
b) the device node cannot be found in the list of phys (yet)

Error a) is permanent (in case of a static DT). Case b) indeed can be
solved by deferring the probe. Why should the framework not return
-EPROBE_DEFER in this case?

>>
>>> +
>>> +     *ptr = phy;
>>> +     devres_add(dev, ptr);
>>> +
>>> +     get_device(&phy->dev);
>>> +
>>> +err0:
>>> +     mutex_unlock(&phy_list_mutex);
>>> +
>>> +     return phy;
>>> +}
>>> +EXPORT_SYMBOL_GPL(devm_of_phy_get);
>>> +

[...]

> Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |


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