Messages in this thread Patch in this message | | | From | Doug Anderson <> | Date | Tue, 31 May 2022 12:28:16 -0700 | Subject | Re: [PATCH] tty: serial: qcom-geni-serial: minor fixes to get_clk_div_rate() |
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Hi,
On Tue, May 31, 2022 at 11:18 AM Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com> wrote: > > Add missing initialisation and correct type casting > > Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com> > --- > drivers/tty/serial/qcom_geni_serial.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c > index 4733a23..08f3ad4 100644 > --- a/drivers/tty/serial/qcom_geni_serial.c > +++ b/drivers/tty/serial/qcom_geni_serial.c > @@ -943,11 +943,11 @@ static int qcom_geni_serial_startup(struct uart_port *uport) > static unsigned long get_clk_div_rate(struct clk *clk, unsigned int baud, > unsigned int sampling_rate, unsigned int *clk_div) > { > - unsigned long ser_clk; > + unsigned long ser_clk = 0;
In this patch it's not at all obvious why you'd need to init to 0. I think the "for loop" is guaranteed to run at least once because "max_div" is known at compile time. ...and currently each time through the "for" loop you'll always set "ser_clk".
I think in a future patch you'll want to _remove_ this from the for loop:
if (!prev) ser_clk = freq;
...and _that's_ when you should init "ser_clk" to 0. Until then I'd leave it as uninitialized...
Honestly, I'd throw all the fixes into one series, too.
> unsigned long desired_clk; > unsigned long freq, prev; > unsigned long div, maxdiv; > - int64_t mult; > + unsigned long long mult; > > desired_clk = baud * sampling_rate; > if (!desired_clk) { > @@ -959,8 +959,8 @@ static unsigned long get_clk_div_rate(struct clk *clk, unsigned int baud, > prev = 0; > > for (div = 1; div <= maxdiv; div++) { > - mult = div * desired_clk; > - if (mult > ULONG_MAX) > + mult = (unsigned long long)div * (unsigned long long)desired_clk;
I think you only need to cast one of the two. The other will be up-cast automatically.
> + if (mult > (unsigned long long)ULONG_MAX)
I don't think you need this cast. As far as I know the C language will "upcast" to the larger of the two types.
-Doug
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