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Subject: media: ccs-pll: Avoid overflow in pre-PLL divisor lower bound search Author: Sakari Ailus <[email protected]> Date: Tue Jul 7 10:31:56 2020 +0200 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 <[email protected]> Signed-off-by: Mauro Carvalho Chehab <[email protected]> drivers/media/i2c/ccs-pll.c | 11 +++++++++-- 1 file 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); _______________________________________________ linuxtv-commits mailing list [email protected] https://www.linuxtv.org/cgi-bin/mailman/listinfo/linuxtv-commits
