drivers/pinctrl: grab default handles from device core
This makes the device core auto-grab the pinctrl handle and set
the "default" (PINCTRL_STATE_DEFAULT) state for every device
that is present in the device model right before probe. This will
account for the lion's share of embedded silicon devcies.
A modification of the semantics for pinctrl_get() is also done:
previously if the pinctrl handle for a certain device was already
taken, the pinctrl core would return an error. Now, since the
core may have already default-grabbed the handle and set its
state to "default", if the handle was already taken, this will
be disregarded and the located, previously instanitated handle
will be returned to the caller.
This way all code in drivers explicitly requesting their pinctrl
handlers will still be functional, and drivers that want to
explicitly retrieve and switch their handles can still do that.
But if the desired functionality is just boilerplate of this
type in the probe() function:
struct pinctrl *p;
p = devm_pinctrl_get_select_default(&dev);
if (IS_ERR(p)) {
if (PTR_ERR(p) == -EPROBE_DEFER)
return -EPROBE_DEFER;
dev_warn(&dev, "no pinctrl handle\n");
}
The discussion began with the addition of such boilerplate
to the omap4 keypad driver:
http://marc.info/?l=linux-input&m=135091157719300&w=2
A previous approach using notifiers was discussed:
http://marc.info/?l=linux-kernel&m=135263661110528&w=2
This failed because it could not handle deferred probes.
This patch alone does not solve the entire dilemma faced:
whether code should be distributed into the drivers or
if it should be centralized to e.g. a PM domain. But it
solves the immediate issue of the addition of boilerplate
to a lot of drivers that just want to grab the default
state. As mentioned, they can later explicitly retrieve
the handle and set different states, and this could as
well be done by e.g. PM domains as it is only related
to a certain struct device * pointer.
ChangeLog v4->v5 (Stephen):
- Simplified the devicecore grab code.
- Deleted a piece of documentation recommending that pins
be mapped to a device rather than hogged.
ChangeLog v3->v4 (Linus):
- Drop overzealous NULL checks.
- Move kref initialization to pinctrl_create().
- Seeking Tested-by from Stephen Warren so we do not disturb
the Tegra platform.
- Seeking ACK on this from Greg (and others who like it) so I
can merge it through the pinctrl subsystem.
ChangeLog v2->v3 (Linus):
- Abstain from using IS_ERR_OR_NULL() in the driver core,
Russell recently sent a patch to remove it. Handle the
NULL case explicitly even though it's a bogus case.
- Make sure we handle probe deferral correctly in the device
core file. devm_kfree() the container on error so we don't
waste memory for devices without pinctrl handles.
- Introduce reference counting into the pinctrl core using
<linux/kref.h> so that we don't release pinctrl handles
that have been obtained for two or more places.
ChangeLog v1->v2 (Linus):
- Only store a pointer in the device struct, and only allocate
this if it's really used by the device.
Change-Id: Ib66cef0978b9d0e90eab57d75325e3051504b750
Cc: Felipe Balbi <balbi@ti.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Mitch Bradley <wmb@firmworks.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: Rickard Andersson <rickard.andersson@stericsson.com>
Cc: Russell King <linux@arm.linux.org.uk>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
[swarren: fixed and simplified error-handling in pinctrl_bind_pins(), to
correctly handle deferred probe. Removed admonition from docs not to use
pinctrl hogs for devices]
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Git-commit: ab78029ecc347debbd737f06688d788bd9d60c1d
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Hanumant Singh <hanumant@codeaurora.org>
diff --git a/Documentation/pinctrl.txt b/Documentation/pinctrl.txt
index aa3350d..e454a6a 100644
--- a/Documentation/pinctrl.txt
+++ b/Documentation/pinctrl.txt
@@ -967,6 +967,18 @@
Pinmux requests from drivers
============================
+When a device driver is about to probe the device core will automatically
+attempt to issue pinctrl_get_select_default() on these devices.
+This way driver writers do not need to add any of the boilerplate code
+of the type found below. However when doing fine-grained state selection
+and not using the "default" state, you may have to do some device driver
+handling of the pinctrl handles and states.
+
+So if you just want to put the pins for a certain device into the default
+state and be done with it, there is nothing you need to do besides
+providing the proper mapping table. The device core will take care of
+the rest.
+
Generally it is discouraged to let individual drivers get and enable pin
control. So if possible, handle the pin control in platform code or some other
place where you have access to all the affected struct device * pointers. In
@@ -1062,6 +1074,51 @@
cleans up and is ready to retry the probing later in the startup process.
+Drivers needing both pin control and GPIOs
+==========================================
+
+Again, it is discouraged to let drivers lookup and select pin control states
+themselves, but again sometimes this is unavoidable.
+
+So say that your driver is fetching its resources like this:
+
+#include <linux/pinctrl/consumer.h>
+#include <linux/gpio.h>
+
+struct pinctrl *pinctrl;
+int gpio;
+
+pinctrl = devm_pinctrl_get_select_default(&dev);
+gpio = devm_gpio_request(&dev, 14, "foo");
+
+Here we first request a certain pin state and then request GPIO 14 to be
+used. If you're using the subsystems orthogonally like this, you should
+nominally always get your pinctrl handle and select the desired pinctrl
+state BEFORE requesting the GPIO. This is a semantic convention to avoid
+situations that can be electrically unpleasant, you will certainly want to
+mux in and bias pins in a certain way before the GPIO subsystems starts to
+deal with them.
+
+The above can be hidden: using the device core, the pinctrl core may be
+setting up the config and muxing for the pins right before the device is
+probing, nevertheless orthogonal to the GPIO subsystem.
+
+But there are also situations where it makes sense for the GPIO subsystem
+to communicate directly with with the pinctrl subsystem, using the latter
+as a back-end. This is when the GPIO driver may call out to the functions
+described in the section "Pin control interaction with the GPIO subsystem"
+above. This only involves per-pin multiplexing, and will be completely
+hidden behind the gpio_*() function namespace. In this case, the driver
+need not interact with the pin control subsystem at all.
+
+If a pin control driver and a GPIO driver is dealing with the same pins
+and the use cases involve multiplexing, you MUST implement the pin controller
+as a back-end for the GPIO driver like this, unless your hardware design
+is such that the GPIO controller can override the pin controller's
+multiplexing state through hardware without the need to interact with the
+pin control system.
+
+
System pin control hogging
==========================
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index cb4528f..7a0d23b 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -22,6 +22,7 @@
obj-$(CONFIG_SYS_HYPERVISOR) += hypervisor.o
obj-$(CONFIG_REGMAP) += regmap/
obj-$(CONFIG_SOC_BUS) += soc.o
+obj-$(CONFIG_PINCTRL) += pinctrl.o
obj-$(CONFIG_SYNC) += sync.o
obj-$(CONFIG_SW_SYNC) += sw_sync.o
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 1b1cbb5..b3a7d6e 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -24,6 +24,7 @@
#include <linux/wait.h>
#include <linux/async.h>
#include <linux/pm_runtime.h>
+#include <linux/pinctrl/devinfo.h>
#include "base.h"
#include "power/power.h"
@@ -257,6 +258,12 @@
WARN_ON(!list_empty(&dev->devres_head));
dev->driver = drv;
+
+ /* If using pinctrl, bind pins now before probing */
+ ret = pinctrl_bind_pins(dev);
+ if (ret)
+ goto probe_failed;
+
if (driver_sysfs_add(dev)) {
printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
__func__, dev_name(dev));
diff --git a/drivers/base/pinctrl.c b/drivers/base/pinctrl.c
new file mode 100644
index 0000000..67a274e
--- /dev/null
+++ b/drivers/base/pinctrl.c
@@ -0,0 +1,69 @@
+/*
+ * Driver core interface to the pinctrl subsystem.
+ *
+ * Copyright (C) 2012 ST-Ericsson SA
+ * Written on behalf of Linaro for ST-Ericsson
+ * Based on bits of regulator core, gpio core and clk core
+ *
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ *
+ * License terms: GNU General Public License (GPL) version 2
+ */
+
+#include <linux/device.h>
+#include <linux/pinctrl/devinfo.h>
+#include <linux/pinctrl/consumer.h>
+#include <linux/slab.h>
+
+/**
+ * pinctrl_bind_pins() - called by the device core before probe
+ * @dev: the device that is just about to probe
+ */
+int pinctrl_bind_pins(struct device *dev)
+{
+ int ret;
+
+ dev->pins = devm_kzalloc(dev, sizeof(*(dev->pins)), GFP_KERNEL);
+ if (!dev->pins)
+ return -ENOMEM;
+
+ dev->pins->p = devm_pinctrl_get(dev);
+ if (IS_ERR(dev->pins->p)) {
+ dev_dbg(dev, "no pinctrl handle\n");
+ ret = PTR_ERR(dev->pins->p);
+ goto cleanup_alloc;
+ }
+
+ dev->pins->default_state = pinctrl_lookup_state(dev->pins->p,
+ PINCTRL_STATE_DEFAULT);
+ if (IS_ERR(dev->pins->default_state)) {
+ dev_dbg(dev, "no default pinctrl state\n");
+ ret = 0;
+ goto cleanup_get;
+ }
+
+ ret = pinctrl_select_state(dev->pins->p, dev->pins->default_state);
+ if (ret) {
+ dev_dbg(dev, "failed to activate default pinctrl state\n");
+ goto cleanup_get;
+ }
+
+ return 0;
+
+ /*
+ * If no pinctrl handle or default state was found for this device,
+ * let's explicitly free the pin container in the device, there is
+ * no point in keeping it around.
+ */
+cleanup_get:
+ devm_pinctrl_put(dev->pins->p);
+cleanup_alloc:
+ devm_kfree(dev, dev->pins);
+ dev->pins = NULL;
+
+ /* Only return deferrals */
+ if (ret != -EPROBE_DEFER)
+ ret = 0;
+
+ return ret;
+}
diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
index e6373f3..5a2fe9a 100644
--- a/drivers/pinctrl/core.c
+++ b/drivers/pinctrl/core.c
@@ -14,6 +14,7 @@
#define pr_fmt(fmt) "pinctrl core: " fmt
#include <linux/kernel.h>
+#include <linux/kref.h>
#include <linux/export.h>
#include <linux/init.h>
#include <linux/device.h>
@@ -727,6 +728,8 @@
return ERR_PTR(ret);
}
+ kref_init(&p->users);
+
/* Add the pinctrl handle to the global list */
list_add_tail(&p->node, &pinctrl_list);
@@ -740,9 +743,17 @@
if (WARN_ON(!dev))
return ERR_PTR(-EINVAL);
+ /*
+ * See if somebody else (such as the device core) has already
+ * obtained a handle to the pinctrl for this device. In that case,
+ * return another pointer to it.
+ */
p = find_pinctrl(dev);
- if (p != NULL)
- return ERR_PTR(-EBUSY);
+ if (p != NULL) {
+ dev_dbg(dev, "obtain a copy of previously claimed pinctrl\n");
+ kref_get(&p->users);
+ return p;
+ }
return create_pinctrl(dev);
}
@@ -798,13 +809,24 @@
}
/**
- * pinctrl_put() - release a previously claimed pinctrl handle
+ * pinctrl_release() - release the pinctrl handle
+ * @kref: the kref in the pinctrl being released
+ */
+void pinctrl_release(struct kref *kref)
+{
+ struct pinctrl *p = container_of(kref, struct pinctrl, users);
+
+ pinctrl_put_locked(p, true);
+}
+
+/**
+ * pinctrl_put() - decrease use count on a previously claimed pinctrl handle
* @p: the pinctrl handle to release
*/
void pinctrl_put(struct pinctrl *p)
{
mutex_lock(&pinctrl_mutex);
- pinctrl_put_locked(p, true);
+ kref_put(&p->users, pinctrl_release);
mutex_unlock(&pinctrl_mutex);
}
EXPORT_SYMBOL_GPL(pinctrl_put);
diff --git a/drivers/pinctrl/core.h b/drivers/pinctrl/core.h
index 232a9f6..fdd350d 100644
--- a/drivers/pinctrl/core.h
+++ b/drivers/pinctrl/core.h
@@ -9,6 +9,7 @@
* License terms: GNU General Public License (GPL) version 2
*/
+#include <linux/kref.h>
#include <linux/mutex.h>
#include <linux/radix-tree.h>
#include <linux/pinctrl/pinconf.h>
@@ -58,6 +59,7 @@
* @state: the current state
* @dt_maps: the mapping table chunks dynamically parsed from device tree for
* this device, if any
+ * @users: reference count
*/
struct pinctrl {
struct list_head node;
@@ -65,6 +67,7 @@
struct list_head states;
struct pinctrl_state *state;
struct list_head dt_maps;
+ struct kref users;
};
/**
diff --git a/include/linux/device.h b/include/linux/device.h
index 810337c..35862c3 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -21,6 +21,7 @@
#include <linux/compiler.h>
#include <linux/types.h>
#include <linux/mutex.h>
+#include <linux/pinctrl/devinfo.h>
#include <linux/pm.h>
#include <linux/atomic.h>
#include <asm/device.h>
@@ -595,6 +596,8 @@
* @pm_domain: Provide callbacks that are executed during system suspend,
* hibernation, system resume and during runtime PM transitions
* along with subsystem-level and driver-level callbacks.
+ * @pins: For device pin management.
+ * See Documentation/pinctrl.txt for details.
* @numa_node: NUMA node this device is close to.
* @dma_mask: Dma mask (if dma'ble device).
* @coherent_dma_mask: Like dma_mask, but for alloc_coherent mapping as not all
@@ -646,6 +649,10 @@
struct dev_pm_info power;
struct dev_pm_domain *pm_domain;
+#ifdef CONFIG_PINCTRL
+ struct dev_pin_info *pins;
+#endif
+
#ifdef CONFIG_NUMA
int numa_node; /* NUMA node this device is close to */
#endif
diff --git a/include/linux/pinctrl/devinfo.h b/include/linux/pinctrl/devinfo.h
new file mode 100644
index 0000000..6e5f8a9
--- /dev/null
+++ b/include/linux/pinctrl/devinfo.h
@@ -0,0 +1,45 @@
+/*
+ * Per-device information from the pin control system.
+ * This is the stuff that get included into the device
+ * core.
+ *
+ * Copyright (C) 2012 ST-Ericsson SA
+ * Written on behalf of Linaro for ST-Ericsson
+ * This interface is used in the core to keep track of pins.
+ *
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ *
+ * License terms: GNU General Public License (GPL) version 2
+ */
+
+#ifndef PINCTRL_DEVINFO_H
+#define PINCTRL_DEVINFO_H
+
+#ifdef CONFIG_PINCTRL
+
+/* The device core acts as a consumer toward pinctrl */
+#include <linux/pinctrl/consumer.h>
+
+/**
+ * struct dev_pin_info - pin state container for devices
+ * @p: pinctrl handle for the containing device
+ * @default_state: the default state for the handle, if found
+ */
+struct dev_pin_info {
+ struct pinctrl *p;
+ struct pinctrl_state *default_state;
+};
+
+extern int pinctrl_bind_pins(struct device *dev);
+
+#else
+
+/* Stubs if we're not using pinctrl */
+
+static inline int pinctrl_bind_pins(struct device *dev)
+{
+ return 0;
+}
+
+#endif /* CONFIG_PINCTRL */
+#endif /* PINCTRL_DEVINFO_H */