pwm: Fix period and polarity in pwm_get() for non-perfect matches

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: 3796ce1 ("pwm: add period and polarity to struct pwm_lookup")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: stable@vger.kernel.org
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/core.c

@@ -606,6 +606,8 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id)
 	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 *dev, const char *con_id)
 		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 *dev, const char *con_id)
 	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;