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    Subject[PATCH 17/20] 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>
    ---
    drivers/pinctrl/core.h | 1 +
    drivers/pinctrl/pinmux.c | 29 ++++++++++++++++++++++-------
    2 files changed, 23 insertions(+), 7 deletions(-)

    diff --git a/drivers/pinctrl/core.h b/drivers/pinctrl/core.h
    index 1290995..64ae1b8 100644
    --- a/drivers/pinctrl/core.h
    +++ b/drivers/pinctrl/core.h
    @@ -92,6 +92,7 @@ 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 8d32380..359f6ac 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 */
    @@ -100,9 +105,9 @@ static int pin_request(struct pinctrl_dev *pctldev,
    }

    /*
    - * If there is no kind of request function for the pin we just assume
    - * we got it by default and proceed.
    - */
    + * If there is no kind of request function for the pin we just assume
    + * we got it by default and proceed.
    + */
    if (gpio_range && ops->gpio_request_enable)
    /* This requests and enables a single GPIO pin */
    status = ops->gpio_request_enable(pctldev, gpio_range, pin);
    @@ -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.
    --
    1.7.5.4


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