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Copy path0031-clk-divider-Fix-divisor-masking-on-64-bit-platforms.patch
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0031-clk-divider-Fix-divisor-masking-on-64-bit-platforms.patch
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From 0668fdf9453f01c4cc02b0fa3bf75079e39b96c3 Mon Sep 17 00:00:00 2001
From: Sebastian Reichel <[email protected]>
Date: Tue, 24 Oct 2023 16:13:50 +0200
Subject: [PATCH 31/77] 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 <[email protected]>
---
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 a2c2b5203b0a9..94b4fb66a60f0 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;
--
2.47.0