Add an explanation why zero width check is needed when generating factor mask using GENMASK() macro.
Signed-off-by: Jernej Skrabec <[email protected]> --- drivers/clk/sunxi-ng/ccu_nkmp.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/clk/sunxi-ng/ccu_nkmp.c b/drivers/clk/sunxi-ng/ccu_nkmp.c index 69dfc6de1c4e..cbcdf664f336 100644 --- a/drivers/clk/sunxi-ng/ccu_nkmp.c +++ b/drivers/clk/sunxi-ng/ccu_nkmp.c @@ -186,6 +186,12 @@ static int ccu_nkmp_set_rate(struct clk_hw *hw, unsigned long rate, ccu_nkmp_find_best(parent_rate, rate, &_nkmp); + /* + * If width is 0, GENMASK() macro may not generate expected mask (0) + * as it falls under undefined behaviour by C standard due to shifts + * which are equal or greater than width of left operand. This can + * be easily avoided by explicitly checking if width is 0. + */ if (nkmp->n.width) n_mask = GENMASK(nkmp->n.width + nkmp->n.shift - 1, nkmp->n.shift); -- 2.21.0
