linux-kernel - [PATCH] pinctrl: pinctrl-single: Fix pcs_parse_bits_in_pinctrl_entry to use _

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Message-ID: <1460530865-29085-1-git-send-email-j-keerthy@ti.com>
Date:	Wed, 13 Apr 2016 12:31:05 +0530
From:	Keerthy <j-keerthy@...com>
To:	<tony@...mide.com>
CC:	<linus.walleij@...aro.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-omap@...r.kernel.org>, <linux-gpio@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <j-keerthy@...com>,
	<t-kristo@...com>, <nsekhar@...com>
Subject: [PATCH] pinctrl: pinctrl-single: Fix pcs_parse_bits_in_pinctrl_entry to use __ffs than ffs

pcs_parse_bits_in_pinctrl_entry uses ffs which gives bit indices
ranging from 1 to MAX. This leads to a corner case where we try to request
the pin number = MAX and fails.

bit_pos value is being calculted using ffs. pin_num_from_lsb uses
bit_pos value. pins array is populated with:

pin + pin_num_from_lsb.

The above is 1 more than usual bit indices as bit_pos uses ffs to compute
first set bit. Hence the last of the pins array is populated with the MAX
value and not MAX - 1 which causes error when we call pin_request.

mask_pos is rightly calculated as ((pcs->fmask) << (bit_pos - 1))
Consequently val_pos and submask are correct.

Hence use __ffs which gives (ffs(x) - 1) as the first bit set.

fixes: 4e7e8017a8 ("pinctrl: pinctrl-single: enhance to configure multiple pins of different modules")
Signed-off-by: Keerthy <j-keerthy@...com>
---

Boot tested on da850-evm

 drivers/pinctrl/pinctrl-single.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/pinctrl/pinctrl-single.c b/drivers/pinctrl/pinctrl-single.c
index 748c047..897b89b 100644
--- a/drivers/pinctrl/pinctrl-single.c
+++ b/drivers/pinctrl/pinctrl-single.c
@@ -1323,9 +1323,9 @@ static int pcs_parse_bits_in_pinctrl_entry(struct pcs_device *pcs,

 		/* Parse pins in each row from LSB */
 		while (mask) {
-			bit_pos = ffs(mask);
+			bit_pos = __ffs(mask);
 			pin_num_from_lsb = bit_pos / pcs->bits_per_pin;
-			mask_pos = ((pcs->fmask) << (bit_pos - 1));
+			mask_pos = ((pcs->fmask) << bit_pos);
 			val_pos = val & mask_pos;
 			submask = mask & mask_pos;

-- 
1.9.1