[PATCH v3 2/2] pwm: th1520: Fix 32-bit build with COMPILE_TEST

[FUJITA Tomonori]

From: FUJITA Tomonori <fujita.tomonori at gmail.com>

Fix the following build error on 32-bit ARM with COMPILE_TEST:

  ERROR: modpost: drivers/pwm/pwm_th1520.ko: symbol '__aeabi_uldivmod' undefined!

The driver divides u64 values when it converts between nanoseconds and
clock cycles. On 32-bit ARM, these divisions are compiled to calls to
__aeabi_uldivmod, which the kernel does not provide.

Use div64_u64() and div64_u64_round_up() for these divisions, in the
same way as C drivers use div64_u64() and DIV64_U64_ROUND_UP(). The
results do not change.

Fixes: 3c180003dffb ("pwm: th1520: Fix missing Kconfig dependencies")
Reported-by: Andreas Hindborg <a.hindborg at kernel.org>
Closes: https://rust-for-linux.zulipchat.com/#narrow/channel/291565-Help/topic/64bit.20division.20in.20.60pwm_th1520.2Ers.60/near/626825599
Suggested-by: Uwe Kleine-König <ukleinek at kernel.org>
Assisted-by: LLM
Signed-off-by: FUJITA Tomonori <fujita.tomonori at gmail.com>
---
 drivers/pwm/pwm_th1520.rs | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/pwm/pwm_th1520.rs b/drivers/pwm/pwm_th1520.rs
index 728993998446..bd05fe49650e 100644
--- a/drivers/pwm/pwm_th1520.rs
+++ b/drivers/pwm/pwm_th1520.rs
@@ -31,6 +31,10 @@
         mem::DevresIoMem,
         Io, //
     },
+    math::{
+        div64_u64,
+        div64_u64_round_up, //
+    },
     of,
     platform,
     prelude::*,
@@ -68,13 +72,13 @@ const fn th1520_pwm_fp(n: u32) -> usize {
 fn ns_to_cycles(ns: u64, rate_hz: u64) -> u64 {
     const NSEC_PER_SEC_U64: u64 = time::NSEC_PER_SEC as u64;
 
-    ns.saturating_mul(rate_hz) / NSEC_PER_SEC_U64
+    div64_u64(ns.saturating_mul(rate_hz), NSEC_PER_SEC_U64)
 }
 
 fn cycles_to_ns(cycles: u32, rate_hz: u64) -> u64 {
     const NSEC_PER_SEC_U64: u64 = time::NSEC_PER_SEC as u64;
 
-    (u64::from(cycles) * NSEC_PER_SEC_U64).div_ceil(rate_hz)
+    div64_u64_round_up(u64::from(cycles) * NSEC_PER_SEC_U64, rate_hz)
 }
 
 /// Hardware-specific waveform representation for TH1520.
-- 
2.43.0