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    Subject[PATCH 5.19 0013/1157] hwmon: (nct6775) Fix platform driver suspend regression
    Date
    From: Zev Weiss <zev@bewilderbeest.net>

    commit f4e6960f4f16b1ca5da16cec7612ecc86402ac05 upstream.

    Commit c3963bc0a0cf ("hwmon: (nct6775) Split core and platform
    driver") introduced a slight change in nct6775_suspend() in order to
    avoid an otherwise-needless symbol export for nct6775_update_device(),
    replacing a call to that function with a simple dev_get_drvdata()
    instead.

    As it turns out, there is no guarantee that nct6775_update_device()
    is ever called prior to suspend. If this happens, the resume function
    ends up writing bad data into the various chip registers, which results
    in a crash shortly after resume.

    To fix the problem, just add the symbol export and return to using
    nct6775_update_device() as was employed previously.

    Reported-by: Zoltán Kővágó <dirty.ice.hu@gmail.com>
    Tested-by: Zoltán Kővágó <dirty.ice.hu@gmail.com>
    Fixes: c3963bc0a0cf ("hwmon: (nct6775) Split core and platform driver")
    Cc: stable@kernel.org
    Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
    Link: https://lore.kernel.org/r/20220810052646.13825-1-zev@bewilderbeest.net
    [groeck: Updated description]
    Signed-off-by: Guenter Roeck <linux@roeck-us.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/hwmon/nct6775-core.c | 3 ++-
    drivers/hwmon/nct6775-platform.c | 2 +-
    drivers/hwmon/nct6775.h | 2 ++
    3 files changed, 5 insertions(+), 2 deletions(-)

    diff --git a/drivers/hwmon/nct6775-core.c b/drivers/hwmon/nct6775-core.c
    index 446964cbae4c..da9ec6983e13 100644
    --- a/drivers/hwmon/nct6775-core.c
    +++ b/drivers/hwmon/nct6775-core.c
    @@ -1480,7 +1480,7 @@ static int nct6775_update_pwm_limits(struct device *dev)
    return 0;
    }

    -static struct nct6775_data *nct6775_update_device(struct device *dev)
    +struct nct6775_data *nct6775_update_device(struct device *dev)
    {
    struct nct6775_data *data = dev_get_drvdata(dev);
    int i, j, err = 0;
    @@ -1615,6 +1615,7 @@ static struct nct6775_data *nct6775_update_device(struct device *dev)
    mutex_unlock(&data->update_lock);
    return err ? ERR_PTR(err) : data;
    }
    +EXPORT_SYMBOL_GPL(nct6775_update_device);

    /*
    * Sysfs callback functions
    diff --git a/drivers/hwmon/nct6775-platform.c b/drivers/hwmon/nct6775-platform.c
    index ab30437221ce..41c97cfacfb8 100644
    --- a/drivers/hwmon/nct6775-platform.c
    +++ b/drivers/hwmon/nct6775-platform.c
    @@ -359,7 +359,7 @@ static int __maybe_unused nct6775_suspend(struct device *dev)
    {
    int err;
    u16 tmp;
    - struct nct6775_data *data = dev_get_drvdata(dev);
    + struct nct6775_data *data = nct6775_update_device(dev);

    if (IS_ERR(data))
    return PTR_ERR(data);
    diff --git a/drivers/hwmon/nct6775.h b/drivers/hwmon/nct6775.h
    index 93f708148e65..be41848c3cd2 100644
    --- a/drivers/hwmon/nct6775.h
    +++ b/drivers/hwmon/nct6775.h
    @@ -196,6 +196,8 @@ static inline int nct6775_write_value(struct nct6775_data *data, u16 reg, u16 va
    return regmap_write(data->regmap, reg, value);
    }

    +struct nct6775_data *nct6775_update_device(struct device *dev);
    +
    bool nct6775_reg_is_word_sized(struct nct6775_data *data, u16 reg);
    int nct6775_probe(struct device *dev, struct nct6775_data *data,
    const struct regmap_config *regmapcfg);
    --
    2.37.1


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