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| author | Jernej Skrabec <jernej.skrabec@siol.net> | 2019-04-03 17:14:04 +0200 |
|---|---|---|
| committer | Maxime Ripard <maxime.ripard@bootlin.com> | 2019-04-04 09:32:32 +0200 |
| commit | 1054e4dd1cbbb7bf5cc836832648f9972134ef67 (patch) | |
| tree | 74ba5e554dbdf3d6b197bed2bdeff31c437ac904 | |
| parent | 2abc330c514fe56c570bb1a6318b054b06a4f72e (diff) | |
clk: sunxi-ng: nkmp: Explain why zero width check is needed
Add an explanation why zero width check is needed when generating factor
mask using GENMASK() macro.
Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
| -rw-r--r-- | drivers/clk/sunxi-ng/ccu_nkmp.c | 6 |
1 files changed, 6 insertions, 0 deletions
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); |