pinmux: forbid mux_usecount to be set at UINT_MAX

If pin_free is called on a pin already freed, mux_usecount is set to
UINT_MAX which is really a bad idea.

This will issue a warning, so that we can correct the code responsible
for the double free.

Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index 1a00658b3ea0..bd83c8b01cd1 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -194,6 +194,11 @@ static const char *pin_free(struct pinctrl_dev *pctldev, int pin,
         }
 
         if (!gpio_range) {
+                /*
+                 * A pin should not be freed more times than allocated.
+                 */
+                if (WARN_ON(!desc->mux_usecount))
+                        return NULL;
                 desc->mux_usecount--;
                 if (desc->mux_usecount)
                         return NULL;