diff options
| -rw-r--r-- | drivers/clk/clk-divider.c | 25 | ||||
| -rw-r--r-- | drivers/clk/clk-divider_test.c | 4 |
2 files changed, 19 insertions, 10 deletions
diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c index b3b485d23ea8..f68216c65d3d 100644 --- a/drivers/clk/clk-divider.c +++ b/drivers/clk/clk-divider.c @@ -15,6 +15,7 @@ #include <linux/err.h> #include <linux/string.h> #include <linux/log2.h> +#include <linux/overflow.h> /* * DOC: basic adjustable divider clock that cannot gate @@ -301,6 +302,7 @@ static int clk_divider_bestdiv(struct clk_hw *hw, struct clk_hw *parent, int i, bestdiv = 0; unsigned long parent_rate, best = 0, now, maxdiv; unsigned long parent_rate_saved = *best_parent_rate; + unsigned long target_parent_rate; if (!rate) rate = 1; @@ -315,15 +317,11 @@ static int clk_divider_bestdiv(struct clk_hw *hw, struct clk_hw *parent, return bestdiv; } - /* - * The maximum divider we can use without overflowing - * unsigned long in rate * i below - */ - maxdiv = min(ULONG_MAX / rate, maxdiv); - for (i = _next_div(table, 0, flags); i <= maxdiv; i = _next_div(table, i, flags)) { - if (rate * i == parent_rate_saved) { + bool overflow = check_mul_overflow(rate, (unsigned long)i, &target_parent_rate); + + if (!overflow && target_parent_rate == parent_rate_saved) { /* * It's the most ideal case if the requested rate can be * divided from parent clock without needing to change @@ -332,13 +330,24 @@ static int clk_divider_bestdiv(struct clk_hw *hw, struct clk_hw *parent, *best_parent_rate = parent_rate_saved; return i; } - parent_rate = clk_hw_round_rate(parent, rate * i); + /* + * Clamp target_parent_rate to ULONG_MAX on overflow. The true + * required parent rate exceeds what can be represented, so ask + * the parent for the highest rate it can produce. There is no + * point continuing the loop past this since larger dividers + * only move further from the requested rate. + */ + if (overflow) + target_parent_rate = ULONG_MAX; + parent_rate = clk_hw_round_rate(parent, target_parent_rate); now = DIV_ROUND_UP_ULL((u64)parent_rate, i); if (_is_best_div(rate, now, best, flags)) { bestdiv = i; best = now; *best_parent_rate = parent_rate; } + if (overflow) + break; } if (!bestdiv) { diff --git a/drivers/clk/clk-divider_test.c b/drivers/clk/clk-divider_test.c index cb56931456b8..8ee1614128d0 100644 --- a/drivers/clk/clk-divider_test.c +++ b/drivers/clk/clk-divider_test.c @@ -61,7 +61,7 @@ static void clk_divider_bestdiv_ulong_max_returns_max_rate(struct kunit *test) * can produce. */ rate = clk_hw_round_rate(div_hw, ULONG_MAX); - KUNIT_EXPECT_EQ(test, rate, PARENT_RATE_1GHZ / 8); + KUNIT_EXPECT_EQ(test, rate, PARENT_RATE_1GHZ / 2); } /* @@ -133,7 +133,7 @@ static void clk_divider_bestdiv_mux_ulong_max_returns_max_rate(struct kunit *tes div_hw)); rate = clk_hw_round_rate(div_hw, ULONG_MAX); - KUNIT_EXPECT_EQ(test, rate, 0); + KUNIT_EXPECT_EQ(test, rate, PARENT_RATE_4GHZ / 2); } static struct kunit_case clk_divider_bestdiv_test_cases[] = { |