[PATCH 4.5 073/200] pinctrl: single: Fix pcs_parse_bits_in_pinctrl_entry to use __ffs than ffs

Greg Kroah-Hartman
2016-05-03T01:15:36Z

From: Keerthy <j-keerthy@ti.com>

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@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/pinctrl/pinctrl-single.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/pinctrl/pinctrl-single.c
+++ b/drivers/pinctrl/pinctrl-single.c
@@ -1273,9 +1273,9 @@ static int pcs_parse_bits_in_pinctrl_ent

/* 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;

@@ -1844,7 +1844,7 @@ static int pcs_probe(struct platform_dev
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. */