linux-kernel - [PATCH 3.2 18/46] Input: pmic8xxx-pwrkey - fix algorithm for converting trigger delay

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Message-ID: <lsq.1465767281.738011432@decadent.org.uk>
Date:	Sun, 12 Jun 2016 22:34:41 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Bjorn Andersson" <bjorn.andersson@...aro.org>,
	"Stephen Boyd" <sboyd@...eaurora.org>,
	"Dmitry Torokhov" <dmitry.torokhov@...il.com>,
	"John Stultz" <john.stultz@...aro.org>
Subject: [PATCH 3.2 18/46] Input: pmic8xxx-pwrkey - fix algorithm for
 converting trigger delay

3.2.81-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Stephen Boyd <sboyd@...eaurora.org>

commit eda5ecc0a6b865561997e177c393f0b0136fe3b7 upstream.

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@...aro.org>
Fixes: 92d57a73e410 ("input: Add support for Qualcomm PMIC8XXX power key")
Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
Tested-by: John Stultz <john.stultz@...aro.org>
Acked-by: Bjorn Andersson <bjorn.andersson@...aro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
[bwh: Backported to 3.2: use pdata->kpd_trigger_delay_us not kpd_delay]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/drivers/input/misc/pmic8xxx-pwrkey.c
+++ b/drivers/input/misc/pmic8xxx-pwrkey.c
@@ -98,7 +98,9 @@ static int __devinit pmic8xxx_pwrkey_pro
 		return -EINVAL;
 	}
 
-	if (pdata->kpd_trigger_delay_us > 62500) {
+	/* Valid range of pwr key trigger delay is 1/64 sec to 2 seconds. */
+	if (pdata->kpd_trigger_delay_us > USEC_PER_SEC * 2 ||
+	    pdata->kpd_trigger_delay_us < USEC_PER_SEC / 64) {
 		dev_err(&pdev->dev, "invalid power key trigger delay\n");
 		return -EINVAL;
 	}
@@ -120,8 +122,8 @@ static int __devinit pmic8xxx_pwrkey_pro
 	pwr->phys = "pmic8xxx_pwrkey/input0";
 	pwr->dev.parent = &pdev->dev;
 
-	delay = (pdata->kpd_trigger_delay_us << 10) / USEC_PER_SEC;
-	delay = 1 + ilog2(delay);
+	delay = (pdata->kpd_trigger_delay_us << 6) / USEC_PER_SEC;
+	delay = ilog2(delay);
 
 	err = pm8xxx_readb(pdev->dev.parent, PON_CNTL_1, &pon_cntl);
 	if (err < 0) {