Messages in this thread | | | Date | Fri, 8 Mar 2019 22:49:31 +0100 | From | Uwe Kleine-König <> | Subject | Re: [PATCH] pwm: img: Turn final 'else if' into 'else' in img_pwm_config |
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On Fri, Mar 08, 2019 at 01:23:41PM -0800, Nick Desaulniers wrote: > On Fri, Mar 8, 2019 at 1:18 PM Uwe Kleine-König > <u.kleine-koenig@pengutronix.de> wrote: > > > > On Fri, Mar 08, 2019 at 10:38:11AM -0800, Nick Desaulniers wrote: > > > On Fri, Mar 8, 2019 at 12:53 AM Uwe Kleine-König > > > <u.kleine-koenig@pengutronix.de> wrote: > > > > > > > > On Thu, Mar 07, 2019 at 03:36:28PM -0700, Nathan Chancellor wrote: > > > > > When building with -Wsometimes-uninitialized, Clang warns: > > > > > > > > > > drivers/pwm/pwm-img.c:126:13: error: variable 'timebase' is used > > > > > uninitialized whenever 'if' condition is false > > > > > [-Werror,-Wsometimes-uninitialized] > > > > > > > > > > The final else if functions as an else; make that explicit so that Clang > > > > > understands that timebase cannot be used uninitialized. > > > > > > > > > > Link: https://github.com/ClangBuiltLinux/linux/issues/400 > > > > > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> > > > > > --- > > > > > drivers/pwm/pwm-img.c | 2 +- > > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > > > diff --git a/drivers/pwm/pwm-img.c b/drivers/pwm/pwm-img.c > > > > > index 815f5333bb8f..1cc5fbe1e1d3 100644 > > > > > --- a/drivers/pwm/pwm-img.c > > > > > +++ b/drivers/pwm/pwm-img.c > > > > > @@ -123,7 +123,7 @@ static int img_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, > > > > > } else if (mul <= max_timebase * 512) { > > > > > div = PWM_CTRL_CFG_SUB_DIV0_DIV1; > > > > > timebase = DIV_ROUND_UP(mul, 512); > > > > > - } else if (mul > max_timebase * 512) { > > > > > + } else { > > > > > dev_err(chip->dev, > > > > > "failed to configure timebase steps/divider value\n"); > > > > > return -EINVAL; > > > > > > > > This can even be simplified further. > > > > > > > > From the probe function we have: > > > > > > > > pwm_chip->max_period_ns = NSEC_PER_SEC * 512 * max_timebase / input_clk_hz > > > > > > I had trouble verifying `input_clk_hz` in the above. The divisor is > > > `clk_get_rate(pwm->pwm_clk)`, but is it guaranteed to always be > > > `input_clk_hz`? If so, where? > > > > In the probe function it's called "clk_rate". We have: > > > > clk_rate = clk_get_rate(pwm->pwm_clk); > > ... > > val = (u64)NSEC_PER_SEC * 512 * pwm->data->max_timebase; > > do_div(val, clk_rate); > > pwm->max_period_ns = val; > > > > and in img_pwm_config we have: > > > > input_clk_hz = clk_get_rate(pwm_chip->pwm_clk); > > > > I used the name used in img_pwm_config with the intention that my > > reasoning is easier to understand, but obviously I failed. > > > > This by the way highlights another patch opportunity: Unify the names > > that the same thing gets the same name in the different functions. This > > doesn't only affect "clk_rate" vs "input_clk_hz", but also "pwm_chip" > > vs. "pwm". > > Sure, those seem like nice little cleanups that will help with > maintainability. Would you mind sending a patch for those, and I'll > review? Otherwise Nathan's patch exists and is ready to go.
I don't mind. But I would prefer to get some input from Thierry about how to round first. I also wonder if there is a publically available manual for this piece of hardware.
Best regards Uwe
-- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ |
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