Input: pmic8xxx-pwrkey - fix algorithm for converting trigger delay

[ Upstream commit eda5ecc0 ]

The trigger delay algorithm that converts from microseconds to
the register value looks incorrect. According to most of the PMIC
documentation, the equation is

	delay (Seconds) = (1 / 1024) * 2 ^ (x + 4)

except for one case where the documentation looks to have a
formatting issue and the equation looks like

	delay (Seconds) = (1 / 1024) * 2 x + 4

Most likely this driver was written with the improper
documentation to begin with. According to the downstream sources
the valid delays are from 2 seconds to 1/64 second, and the
latter equation just doesn't make sense for that. Let's fix the
algorithm and the range check to match the documentation and the
downstream sources.
Reported-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Fixes: 92d57a73 ("input: Add support for Qualcomm PMIC8XXX power key")
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Tested-by: John Stultz <john.stultz@linaro.org>
Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

drivers/input/misc/pmic8xxx-pwrkey.c

@@ -92,7 +92,8 @@ static int pmic8xxx_pwrkey_probe(struct platform_device *pdev)
 	if (of_property_read_u32(pdev->dev.of_node, "debounce", &kpd_delay))
 		kpd_delay = 15625;
 
-	if (kpd_delay > 62500 || kpd_delay == 0) {
+	/* Valid range of pwr key trigger delay is 1/64 sec to 2 seconds. */
+	if (kpd_delay > USEC_PER_SEC * 2 || kpd_delay < USEC_PER_SEC / 64) {
 		dev_err(&pdev->dev, "invalid power key trigger delay\n");
 		return -EINVAL;
 	}
@@ -122,8 +123,8 @@ static int pmic8xxx_pwrkey_probe(struct platform_device *pdev)
 	pwr->name = "pmic8xxx_pwrkey";
 	pwr->phys = "pmic8xxx_pwrkey/input0";
 
-	delay = (kpd_delay << 10) / USEC_PER_SEC;
-	delay = 1 + ilog2(delay);
+	delay = (kpd_delay << 6) / USEC_PER_SEC;
+	delay = ilog2(delay);
 
 	err = regmap_read(regmap, PON_CNTL_1, &pon_cntl);
 	if (err < 0) {