5.15-stable review patch. If anyone has any objections, please let me know.
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From: Uwe Kleine-König u.kleine-koenig@baylibre.com
[ Upstream commit e7327c193014a4d8666e9c1cda09cf2c060518e8 ]
There were several issues in the function rcar_pwm_set_counter():
- The u64 values period_ns and duty_ns were cast to int on function call which might loose bits on 32 bit architectures. Fix: Make parameters to rcar_pwm_set_counter() u64 - The algorithm divided by the result of a division which looses precision. Fix: Make use of mul_u64_u64_div_u64() - The calculated values were just masked to fit the respective register fields which again might loose bits. Fix: Explicitly check for overlow
Implement the respective fixes.
A side effect of fixing the 2nd issue is that there is no division by 0 if clk_get_rate() returns 0.
Fixes: ed6c1476bf7f ("pwm: Add support for R-Car PWM Timer") Signed-off-by: Uwe Kleine-König u.kleine-koenig@baylibre.com Link: https://lore.kernel.org/r/ab3dac794b2216cc1cc56d65c93dd164f8bd461b.174350168... [ukleinek: Added an explicit #include <linux/bitfield.h> to please the 0day build bot] Link: https://lore.kernel.org/oe-kbuild-all/202504031354.VJtxScP5-lkp@intel.com/ Reviewed-by: Geert Uytterhoeven geert+renesas@glider.be Signed-off-by: Uwe Kleine-König ukleinek@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/pwm/pwm-rcar.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-)
diff --git a/drivers/pwm/pwm-rcar.c b/drivers/pwm/pwm-rcar.c index 55f46d09602b1..b2e75d870532e 100644 --- a/drivers/pwm/pwm-rcar.c +++ b/drivers/pwm/pwm-rcar.c @@ -8,6 +8,7 @@ * - The hardware cannot generate a 0% duty cycle. */
+#include <linux/bitfield.h> #include <linux/clk.h> #include <linux/err.h> #include <linux/io.h> @@ -103,23 +104,24 @@ static void rcar_pwm_set_clock_control(struct rcar_pwm_chip *rp, rcar_pwm_write(rp, value, RCAR_PWMCR); }
-static int rcar_pwm_set_counter(struct rcar_pwm_chip *rp, int div, int duty_ns, - int period_ns) +static int rcar_pwm_set_counter(struct rcar_pwm_chip *rp, int div, u64 duty_ns, + u64 period_ns) { - unsigned long long one_cycle, tmp; /* 0.01 nanoseconds */ + unsigned long long tmp; unsigned long clk_rate = clk_get_rate(rp->clk); u32 cyc, ph;
- one_cycle = NSEC_PER_SEC * 100ULL << div; - do_div(one_cycle, clk_rate); + /* div <= 24 == RCAR_PWM_MAX_DIVISION, so the shift doesn't overflow. */ + tmp = mul_u64_u64_div_u64(period_ns, clk_rate, (u64)NSEC_PER_SEC << div); + if (tmp > FIELD_MAX(RCAR_PWMCNT_CYC0_MASK)) + tmp = FIELD_MAX(RCAR_PWMCNT_CYC0_MASK);
- tmp = period_ns * 100ULL; - do_div(tmp, one_cycle); - cyc = (tmp << RCAR_PWMCNT_CYC0_SHIFT) & RCAR_PWMCNT_CYC0_MASK; + cyc = FIELD_PREP(RCAR_PWMCNT_CYC0_MASK, tmp);
- tmp = duty_ns * 100ULL; - do_div(tmp, one_cycle); - ph = tmp & RCAR_PWMCNT_PH0_MASK; + tmp = mul_u64_u64_div_u64(duty_ns, clk_rate, (u64)NSEC_PER_SEC << div); + if (tmp > FIELD_MAX(RCAR_PWMCNT_PH0_MASK)) + tmp = FIELD_MAX(RCAR_PWMCNT_PH0_MASK); + ph = FIELD_PREP(RCAR_PWMCNT_PH0_MASK, tmp);
/* Avoid prohibited setting */ if (cyc == 0 || ph == 0)