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    Subject[PATCH 3.16 033/357] pwm: Fix period and polarity in pwm_get() for non-perfect matches
    Date
    3.16-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Geert Uytterhoeven <geert+renesas@glider.be>

    commit d717ea73e36dd5659640fae82605ad85c4117f4d upstream.

    If pwm_get() finds a look-up entry with a perfect match (both dev_id and
    con_id match), the loop is aborted, and "p" still points to the correct
    struct pwm_lookup.

    If only an entry with a matching dev_id or con_id is found, the loop
    terminates after traversing the whole list, and "p" now points to
    arbitrary memory, not part of the pwm_lookup list.
    Then pwm_set_period() and pwm_set_polarity() will set random values for
    period resp. polarity.

    To fix this, save period and polarity when finding a new best match,
    just like is done for chip (for the provider) and index.

    This fixes the LCD backlight on r8a7740/armadillo-legacy, which was fed
    period 0 and polarity -1068821144 instead of 33333 resp. 1.

    Fixes: 3796ce1d4d4b ("pwm: add period and polarity to struct pwm_lookup")
    Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
    Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/pwm/core.c | 8 ++++++--
    1 file changed, 6 insertions(+), 2 deletions(-)

    --- a/drivers/pwm/core.c
    +++ b/drivers/pwm/core.c
    @@ -606,6 +606,8 @@ struct pwm_device *pwm_get(struct device
    unsigned int best = 0;
    struct pwm_lookup *p;
    unsigned int match;
    + unsigned int period;
    + enum pwm_polarity polarity;

    /* look up via DT first */
    if (IS_ENABLED(CONFIG_OF) && dev && dev->of_node)
    @@ -653,6 +655,8 @@ struct pwm_device *pwm_get(struct device
    if (match > best) {
    chip = pwmchip_find_by_name(p->provider);
    index = p->index;
    + period = p->period;
    + polarity = p->polarity;

    if (match != 3)
    best = match;
    @@ -668,8 +672,8 @@ struct pwm_device *pwm_get(struct device
    if (IS_ERR(pwm))
    return pwm;

    - pwm_set_period(pwm, p->period);
    - pwm_set_polarity(pwm, p->polarity);
    + pwm_set_period(pwm, period);
    + pwm_set_polarity(pwm, polarity);


    return pwm;



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