diff options
| author | Sakari Ailus <sakari.ailus@linux.intel.com> | 2020-07-07 10:31:56 +0200 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab+huawei@kernel.org> | 2020-12-07 15:49:32 +0100 |
| commit | 482e75e7b3eba6730cbfaa1911916d13887c9606 (patch) | |
| tree | c522a03b0601df1de45141f49e6def813a1bcee7 /drivers/media | |
| parent | fe52ece8d2e26bd4d38e2c99a7cd13d944c1ee98 (diff) | |
media: ccs-pll: Avoid overflow in pre-PLL divisor lower bound search
The external clock frequency times the PLL multiplier may exceed the value
range of 32-bit unsigned integers. Instead perform the same calculation y
using two divisions.
The result has some potential to be different, but that's ok: this number
is used to limit the range of pre-PLL divisors to find optimal values. So
the effect of the rare case of a different result here would mean an
invalid pre-PLL divisor is tried. That will be found out a little later in
any case.
Also guard against dividing by zero if the external clock frequency is
higher than the maximum OP PLL output clock --- a rather improbable case.
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Diffstat (limited to 'drivers/media')
| -rw-r--r-- | drivers/media/i2c/ccs-pll.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/drivers/media/i2c/ccs-pll.c b/drivers/media/i2c/ccs-pll.c index b45e6b30c528..78897a7c1448 100644 --- a/drivers/media/i2c/ccs-pll.c +++ b/drivers/media/i2c/ccs-pll.c @@ -40,6 +40,11 @@ static inline uint32_t is_one_or_even(uint32_t a) return 1; } +static inline uint32_t one_or_more(uint32_t a) +{ + return a ?: 1; +} + static int bounds_check(struct device *dev, uint32_t val, uint32_t min, uint32_t max, char *str) { @@ -458,8 +463,10 @@ int ccs_pll_calculate(struct device *dev, const struct ccs_pll_limits *lim, min_op_pre_pll_clk_div = max_t(uint16_t, min_op_pre_pll_clk_div, clk_div_even_up( - DIV_ROUND_UP(mul * pll->ext_clk_freq_hz, - op_lim_fr->max_pll_op_clk_freq_hz))); + mul / + one_or_more( + DIV_ROUND_UP(op_lim_fr->max_pll_op_clk_freq_hz, + pll->ext_clk_freq_hz)))); dev_dbg(dev, "pll_op check: min / max op_pre_pll_clk_div: %u / %u\n", min_op_pre_pll_clk_div, max_op_pre_pll_clk_div); |