clk: sunxi-ng: nkmp: Explain why zero width check is needed (1054e4dd) · Commits · 戴 / test

Add an explanation why zero width check is needed when generating factor mask using GENMASK() macro. Signed-off-by:

drivers/clk/sunxi-ng/ccu_nkmp.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -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);