On 16/05/17 23:56, Gustavo A. R. Silva wrote:
Hello everybody,
While looking into Coverity ID 1408721 I ran into the following piece of
code at /drivers/pwm/pwm-mediatek.c:77:
77static int mtk_pwm_config(struct pwm_chip *chip, struct pwm_device
*pwm,
78 int duty_ns, int period_ns)
79{
80 struct mtk_pwm_chip *pc = to_mtk_pwm_chip(chip);
81 struct clk *clk = pc->clks[MTK_CLK_PWM1 + pwm->hwpwm];
82 u32 resolution, clkdiv = 0;
83
84 resolution = NSEC_PER_SEC / clk_get_rate(clk);
85
86 while (period_ns / resolution > 8191) {
87 resolution *= 2;
88 clkdiv++;
89 }
90
91 if (clkdiv > 7)
92 return -EINVAL;
93
94 mtk_pwm_writel(pc, pwm->hwpwm, PWMCON, BIT(15) | BIT(3) |
clkdiv);
95 mtk_pwm_writel(pc, pwm->hwpwm, PWMDWIDTH, period_ns /
resolution);
96 mtk_pwm_writel(pc, pwm->hwpwm, PWMTHRES, duty_ns / resolution);
97
98 return 0;
99}
The issue here is that in case _clk_ is null, function clk_get_rate() at
line 84 will return zero and a division by zero will occur.
So my question here is if there is any chance for _clk_ to be null at
line 81, hence ending up triggering a division by zero at line 84?
No it can't, in the probe function will error out if one of the seven
clocks are not found.
for (i = 0; i < MTK_CLK_MAX; i++) {
pc->clks[i] = devm_clk_get(&pdev->dev, mtk_pwm_clk_name[i]);
if (IS_ERR(pc->clks[i]))
return PTR_ERR(pc->clks[i]);
}
It registers a pwm chip with five PWMs. When the config function is
called one of the five PWMs is identified (with a value from 0-4) which
correspondents to the MTK_CLK_PWM[1-5], so no bug here neither.
Regards,
Matthias
I'm trying to figure out if this is a false positive or something that
needs to be fixed.
I'd really appreciate any comment on this.
Thank you
--
Gustavo A. R. Silva
