[4.2.y-ckt stable] Patch "pinctrl: single: Fix pcs_parse_bits_in_pinctrl_entry to use __ffs than ffs" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    pinctrl: single: Fix pcs_parse_bits_in_pinctrl_entry to use __ffs than ffs

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt9.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 317d73cda0cc9451fa2ff2224b5ed65f34623a8a Mon Sep 17 00:00:00 2001
From: Keerthy <j-keerthy at ti.com>
Date: Thu, 14 Apr 2016 10:29:16 +0530
Subject: pinctrl: single: Fix pcs_parse_bits_in_pinctrl_entry to use __ffs
 than ffs

commit 56b367c0cd67d4c3006738e7dc9dda9273fd2bfe upstream.

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 at ti.com>
Acked-by: Tony Lindgren <tony at atomide.com>
Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/pinctrl/pinctrl-single.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/pinctrl/pinctrl-single.c b/drivers/pinctrl/pinctrl-single.c
index 9b24b343..99835c1 100644
--- a/drivers/pinctrl/pinctrl-single.c
+++ b/drivers/pinctrl/pinctrl-single.c
@@ -1273,9 +1273,9 @@ 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;

@@ -1852,7 +1852,7 @@ static int pcs_probe(struct platform_device *pdev)
 	ret = of_property_read_u32(np, "pinctrl-single,function-mask",
 				   &pcs->fmask);
 	if (!ret) {
-		pcs->fshift = ffs(pcs->fmask) - 1;
+		pcs->fshift = __ffs(pcs->fmask);
 		pcs->fmax = pcs->fmask >> pcs->fshift;
 	} else {
 		/* If mask property doesn't exist, function mux is invalid. */
--
2.7.4