From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Sebastian Reichel Date: Tue, 24 Oct 2023 16:09:35 +0200 Subject: math.h: add DIV_ROUND_UP_NO_OVERFLOW Add a new DIV_ROUND_UP helper, which cannot overflow when big numbers are being used. Signed-off-by: Sebastian Reichel --- include/linux/math.h | 11 ++++++++++ 1 file changed, 11 insertions(+) diff --git a/include/linux/math.h b/include/linux/math.h index dd4152711de7..f80bfb375ab9 100644 --- a/include/linux/math.h +++ b/include/linux/math.h @@ -36,6 +36,17 @@ #define DIV_ROUND_UP __KERNEL_DIV_ROUND_UP +/** + * DIV_ROUND_UP_NO_OVERFLOW - divide two numbers and always round up + * @n: numerator / dividend + * @d: denominator / divisor + * + * This functions does the same as DIV_ROUND_UP, but internally uses a + * division and a modulo operation instead of math tricks. This way it + * avoids overflowing when handling big numbers. + */ +#define DIV_ROUND_UP_NO_OVERFLOW(n, d) (((n) / (d)) + !!((n) % (d))) + #define DIV_ROUND_DOWN_ULL(ll, d) \ ({ unsigned long long _tmp = (ll); do_div(_tmp, d); _tmp; }) -- Armbian From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Sebastian Reichel Date: Tue, 24 Oct 2023 16:13:50 +0200 Subject: clk: divider: Fix divisor masking on 64 bit platforms The clock framework handles clock rates as "unsigned long", so u32 on 32-bit architectures and u64 on 64-bit architectures. The current code casts the dividend to u64 on 32-bit to avoid a potential overflow. For example DIV_ROUND_UP(3000000000, 1500000000) = (3.0G + 1.5G - 1) / 1.5G = = OVERFLOW / 1.5G, which has been introduced in commit 9556f9dad8f5 ("clk: divider: handle integer overflow when dividing large clock rates"). On 64 bit platforms this masks the divisor, so that only the lower 32 bit are used. Thus requesting a frequency >= 4.3GHz results in incorrect values. For example requesting 4300000000 (4.3 GHz) will effectively request ca. 5 MHz. Requesting clk_round_rate(clk, ULONG_MAX) is a bit of a special case, since that still returns correct values as long as the parent clock is below 8.5 GHz. Fix this by switching to DIV_ROUND_UP_NO_OVERFLOW, which cannot overflow. This avoids any requirements on the arguments (except that divisor should not be 0 obviously). Signed-off-by: Sebastian Reichel --- drivers/clk/clk-divider.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c index a2c2b5203b0a..94b4fb66a60f 100644 --- a/drivers/clk/clk-divider.c +++ b/drivers/clk/clk-divider.c @@ -220,7 +220,7 @@ static int _div_round_up(const struct clk_div_table *table, unsigned long parent_rate, unsigned long rate, unsigned long flags) { - int div = DIV_ROUND_UP_ULL((u64)parent_rate, rate); + int div = DIV_ROUND_UP_NO_OVERFLOW(parent_rate, rate); if (flags & CLK_DIVIDER_POWER_OF_TWO) div = __roundup_pow_of_two(div); @@ -237,7 +237,7 @@ static int _div_round_closest(const struct clk_div_table *table, int up, down; unsigned long up_rate, down_rate; - up = DIV_ROUND_UP_ULL((u64)parent_rate, rate); + up = DIV_ROUND_UP_NO_OVERFLOW(parent_rate, rate); down = parent_rate / rate; if (flags & CLK_DIVIDER_POWER_OF_TWO) { @@ -473,7 +473,7 @@ int divider_get_val(unsigned long rate, unsigned long parent_rate, { unsigned int div, value; - div = DIV_ROUND_UP_ULL((u64)parent_rate, rate); + div = DIV_ROUND_UP_NO_OVERFLOW(parent_rate, rate); if (!_is_valid_div(table, div, flags)) return -EINVAL; -- Armbian From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Sebastian Reichel Date: Tue, 24 Oct 2023 18:09:57 +0200 Subject: clk: composite: replace open-coded abs_diff() Replace the open coded abs_diff() with the existing helper function. Suggested-by: Andy Shevchenko Signed-off-by: Sebastian Reichel --- drivers/clk/clk-composite.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/drivers/clk/clk-composite.c b/drivers/clk/clk-composite.c index 66759fe28fad..478a4e594336 100644 --- a/drivers/clk/clk-composite.c +++ b/drivers/clk/clk-composite.c @@ -6,6 +6,7 @@ #include #include #include +#include #include static u8 clk_composite_get_parent(struct clk_hw *hw) @@ -119,10 +120,7 @@ static int clk_composite_determine_rate(struct clk_hw *hw, if (ret) continue; - if (req->rate >= tmp_req.rate) - rate_diff = req->rate - tmp_req.rate; - else - rate_diff = tmp_req.rate - req->rate; + rate_diff = abs_diff(req->rate, tmp_req.rate); if (!rate_diff || !req->best_parent_hw || best_rate_diff > rate_diff) { -- Armbian