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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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