From: Steve Dunnagan Date: Wed, 1 Jul 2026 19:59:20 +0000 (-0400) Subject: firmware: arm_scmi: Use 64-bit division for clock rate rounding X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bf1deecccf210d1dd84e85cd4a45070888583984;p=thirdparty%2Fkernel%2Flinux.git firmware: arm_scmi: Use 64-bit division for clock rate rounding SCMI clock range descriptors report rates as 64-bit values. When handling a range clock, scmi_clock_determine_rate() rounds the requested rate up to the next supported step using the SCMI RATE_STEP value. The current code uses div64_ul() for this calculation. Since div64_ul() takes an unsigned long divisor, the 64-bit RATE_STEP value can be truncated on 32-bit builds. In the worst case, a non-zero 64-bit step can be narrowed to zero before the division. Store RATE_STEP in a u64, reject a malformed zero step, and use DIV64_U64_ROUND_UP() so the divisor is handled as a 64-bit value. This does not change behavior for valid firmware reporting a non-zero step that fits in unsigned long. Tested on Xunlong Orange Pi 5 Plus / RK3588 with SCMI over SMC. SCMI clocks probed successfully before and after the change. SCMI-backed CPU clocks were exercised through cpufreq-dt by switching each CPU policy between its lowest and highest available OPP. Fixes: ecde921eb460 ("firmware: arm_scmi: Add clock determine_rate operation") Signed-off-by: Steve Dunnagan Link: https://patch.msgid.link/20260701195923.444270-1-sdunnaga@redhat.com Signed-off-by: Sudeep Holla --- diff --git a/drivers/firmware/arm_scmi/clock.c b/drivers/firmware/arm_scmi/clock.c index 42e666a628c7..0278705d809e 100644 --- a/drivers/firmware/arm_scmi/clock.c +++ b/drivers/firmware/arm_scmi/clock.c @@ -718,7 +718,7 @@ static int scmi_clock_rate_set(const struct scmi_protocol_handle *ph, static int scmi_clock_determine_rate(const struct scmi_protocol_handle *ph, u32 clk_id, unsigned long *rate) { - u64 fmin, fmax, ftmp; + u64 fmin, fmax, ftmp, step; struct scmi_clock_info *clk; struct scmi_clock_desc *clkd; struct clock_info *ci = ph->get_priv(ph); @@ -749,11 +749,14 @@ static int scmi_clock_determine_rate(const struct scmi_protocol_handle *ph, return 0; } + step = clkd->r.rates[RATE_STEP]; + if (!step) + return -EINVAL; + ftmp = *rate - fmin; - ftmp += clkd->r.rates[RATE_STEP] - 1; /* to round up */ - ftmp = div64_ul(ftmp, clkd->r.rates[RATE_STEP]); + ftmp = DIV64_U64_ROUND_UP(ftmp, step); - *rate = ftmp * clkd->r.rates[RATE_STEP] + fmin; + *rate = ftmp * step + fmin; return 0; }