Il 06/07/23 14:29, Alexandre Mergnat ha scritto:
On 06/07/2023 12:04, Shuijing Li wrote:There is a coverity issue in the original mtk_disp_pwm_get_state() function. In function call DIV64_U64_ROUND_UP, division by expression Which may be zero has undefined behavior. Fix this accordingly. Signed-off-by: Shuijing Li <shuijing.li@xxxxxxxxxxxx> --- drivers/pwm/pwm-mtk-disp.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c index 79e321e96f56..ca00058a6ef4 100644 --- a/drivers/pwm/pwm-mtk-disp.c +++ b/drivers/pwm/pwm-mtk-disp.c @@ -196,6 +196,14 @@ static int mtk_disp_pwm_get_state(struct pwm_chip *chip, return err; } + rate = clk_get_rate(mdp->clk_main); + if (rate <= 0) { + dev_err(chip->dev, "Can't get rate: %pe\n", ERR_PTR(rate)); + clk_disable_unprepare(mdp->clk_mm); + clk_disable_unprepare(mdp->clk_main); + return err; + } + /* * Apply DISP_PWM_DEBUG settings to choose whether to enable or disable * registers double buffer and manual commit to working register before @@ -206,7 +214,6 @@ static int mtk_disp_pwm_get_state(struct pwm_chip *chip, mdp->data->bls_debug_mask, mdp->data->bls_debug_mask); - rate = clk_get_rate(mdp->clk_main); con0 = readl(mdp->base + mdp->data->con0); con1 = readl(mdp->base + mdp->data->con1); pwm_en = readl(mdp->base + DISP_PWM_EN);IMHO, it should be done int the function `mtk_disp_pwm_apply` too. Do you agree ?
I think that realistically this will never happen. We're getting the clk_main clock's handle at probe time (or fail and get out), then the PWM clock never has the CLK_GET_RATE_NOCACHE flag, as there wouldn't be any reason to not cache the rates for this clock. But even if we had the CLK_GET_RATE_NOCACHE flag, it wouldn't change much, as our validation actually happens at probe time... This means that our call to clk_get_rate is guaranteed to have a not NULL pointer to this clock's `struct clk_core` and, unless the declaration of this clock in the clock controller driver was wrong, for it, or for its parent, the branch... if (!core->num_parents || core->parent) return core->rate; ...is always satisfied, so, in the end, this instance of clk_get_rate() can't really return zero. If you got such an issue, I suggest to check what the problem is, as it is likely to be outside of this driver. ...that, besides the fact that the proposed code is incorrect, as clk_get_rate() returns an `unsigned long`, so `rate` can never be less than zero, anyway. Cheers, Angelo
