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Subject[PATCH V3 3/7] pinctrl: Add usecount to pins for muxing
Date
Multiple mapping table entries could reference the same pin, and hence
"own" it. This would be unusual now that pinctrl_get() represents a single
state for a client device, but in the future when it represents all known
states for a device, this is quite likely. Implement reference counting
for pin ownership to handle this.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Dong Aisheng <dong.aisheng@linaro.org>
---
v3: Rebased. No logical changes.
v2: Added kerneldoc for @usecount and @owner fields - the latter was
missing from a previous patch.
---
drivers/pinctrl/core.h | 10 +++++++++-
drivers/pinctrl/pinmux.c | 23 +++++++++++++++++++----
2 files changed, 28 insertions(+), 5 deletions(-)
diff --git a/drivers/pinctrl/core.h b/drivers/pinctrl/core.h
index 5f258b7..0bc52ec 100644
--- a/drivers/pinctrl/core.h
+++ b/drivers/pinctrl/core.h
@@ -82,7 +82,14 @@ struct pinctrl_setting {
* @name: a name for the pin, e.g. the name of the pin/pad/finger on a
* datasheet or such
* @dynamic_name: if the name of this pin was dynamically allocated
- * @owner: the device holding this pin or NULL of no device has claimed it
+ * @usecount: If zero, the pin is not claimed, and @owner should be NULL.
+ * If non-zero, this pin is claimed by @owner. This field is an integer
+ * rather than a boolean, since pinctrl_get() might process multiple
+ * mapping table entries that refer to, and hence claim, the same group
+ * or pin, and each of these will increment the @usecount.
+ * @owner: The name of the entity owning the pin. Typically, this is the name
+ * of the device that called pinctrl_get(). Alternatively, it may be the
+ * name of the GPIO passed to pinctrl_request_gpio().
*/
struct pin_desc {
struct pinctrl_dev *pctldev;
@@ -90,6 +97,7 @@ struct pin_desc {
bool dynamic_name;
/* These fields only added when supporting pinmux drivers */
#ifdef CONFIG_PINMUX
+ unsigned usecount;
const char *owner;
#endif
};
diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index f0fb98d..56ca42e 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -83,11 +83,16 @@ static int pin_request(struct pinctrl_dev *pctldev,
goto out;
}

- if (desc->owner && strcmp(desc->owner, owner)) {
+ if (desc->usecount && strcmp(desc->owner, owner)) {
dev_err(pctldev->dev,
"pin already requested\n");
goto out;
}
+
+ desc->usecount++;
+ if (desc->usecount > 1)
+ return 0;
+
desc->owner = owner;

/* Let each pin increase references to this module */
@@ -111,12 +116,18 @@ static int pin_request(struct pinctrl_dev *pctldev,
else
status = 0;

- if (status)
+ if (status) {
dev_err(pctldev->dev, "->request on device %s failed for pin %d\n",
pctldev->desc->name, pin);
+ module_put(pctldev->owner);
+ }
+
out_free_pin:
- if (status)
- desc->owner = NULL;
+ if (status) {
+ desc->usecount--;
+ if (!desc->usecount)
+ desc->owner = NULL;
+ }
out:
if (status)
dev_err(pctldev->dev, "pin-%d (%s) status %d\n",
@@ -150,6 +161,10 @@ static const char *pin_free(struct pinctrl_dev *pctldev, int pin,
return NULL;
}

+ desc->usecount--;
+ if (desc->usecount)
+ return NULL;
+
/*
* If there is no kind of request function for the pin we just assume
* we got it by default and proceed.
--
1.7.0.4


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