Messages in this thread | | | From | Nixiaoming <> | Subject | RE: [PATCH] clk:mmp: clk-mix.c fix divide-by-zero | Date | Sat, 30 Mar 2019 02:20:27 +0000 |
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On 3/30/2019 6:48 AM Stephen Boyd wrote: >Quoting nixiaoming (2019-03-29 04:46:00) >> The _get_div function has a branch with a return value of 0 >> Add a check on the return value of _get_div to avoid divide-by-zero >> >> Signed-off-by: nixiaoming <nixiaoming@huawei.com> > >Similar questions apply here as they do on the generic divider patch you >sent. > _get_div() in both files is a different function, with a divide-by-zero problem I will organize it into a patch set later.
>> --- >> drivers/clk/mmp/clk-mix.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/drivers/clk/mmp/clk-mix.c b/drivers/clk/mmp/clk-mix.c >> index 90814b2..9d152c2 100644 >> --- a/drivers/clk/mmp/clk-mix.c >> +++ b/drivers/clk/mmp/clk-mix.c >> @@ -245,6 +245,8 @@ static int mmp_clk_mix_determine_rate(struct clk_hw *hw, >> div_val_max = _get_maxdiv(mix); >> for (j = 0; j < div_val_max; j++) { >> div = _get_div(mix, j); >> + if (!div) /* avoid divide-by-zero */ > >Why can't we return 1 for the divider value here?
I personally understand that an exception or skip should be thrown after dividing by 0. Directly modified to other values, I am not sure whether it affects the logic My logical understanding of this code is not clear enough, I still need your guidance. > >> + continue; >> mix_rate = parent_rate / div; >> gap = abs(mix_rate - req->rate); >> if (!parent_best || gap < gap_best) { >> @@ -341,6 +343,8 @@ static unsigned long mmp_clk_mix_recalc_rate(struct clk_hw *hw, >> shift = mix->reg_info.shift_div; >> >> div = _get_div(mix, MMP_CLK_BITS_GET_VAL(mux_div, width, shift)); >> + if (!div) /* avoid divide-by-zero */ > >Same question. I personally understand that an exception or skip should be thrown after dividing by 0. Directly modified to other values, I am not sure whether it affects the logic My logical understanding of this code is not clear enough, I still need your guidance. > >> + return -EINVAL; >> >> return parent_rate / div; >> } >
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