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Fix PWM motor-role double-counting in pwmEnsureEnoughtMotors() #11787

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Fix PWM motor-role double-counting in pwmEnsureEnoughtMotors() #11787

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024d92e
Fix PWM motor-role double-counting in pwmEnsureEnoughtMotors()
sensei-hacker Aug 17, 2026
e96746c
Retrigger CI: transient upload-artifacts infra failure (429/503 downl…
sensei-hacker Aug 17, 2026
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10 changes: 9 additions & 1 deletion src/main/drivers/pwm_mapping.c
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Original file line number Diff line number Diff line change
Expand Up @@ -274,6 +274,13 @@ void pwmEnsureEnoughtMotors(uint8_t motorCount)
{
uint8_t motorOnlyOutputs = 0;

// pwmClaimTimer() syncs every sibling pad sharing a physical timer as soon
// as the first motor-only pad in a group is processed, so later siblings
// already satisfy TIM_IS_MOTOR_ONLY on their own turn below. Without this
// guard each of them would be counted again, inflating motorOnlyOutputs
// for an n-pad shared-timer group to 2n-1 instead of n.
bool timerCounted[HARDWARE_TIMER_DEFINITION_COUNT] = { false };

for (int idx = 0; idx < timerHardwareCount; idx++) {
timerHardware_t *timHw = &timerHardware[idx];

Expand All @@ -283,7 +290,8 @@ void pwmEnsureEnoughtMotors(uint8_t motorCount)
continue;
}

if (TIM_IS_MOTOR_ONLY(timHw->usageFlags)) {
if (TIM_IS_MOTOR_ONLY(timHw->usageFlags) && !timerCounted[timer2id(timHw->tim)]) {
timerCounted[timer2id(timHw->tim)] = true;
motorOnlyOutputs++;
motorOnlyOutputs += pwmClaimTimer(timHw->tim, timHw->usageFlags);
Comment on lines +293 to 296

@qodo-free-for-open-source-projects qodo-free-for-open-source-projects Bot Aug 17, 2026

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1. Motor outputs undercounted 🐞 Bug ≡ Correctness

Pass 1 now de-duplicates motor-only counting per physical timer, but it only adds 1 +
pwmClaimTimer(changed), so a timer whose channels are already TIM_USE_MOTOR contributes just 1
regardless of how many motor pads it has. This undercount can make pass 2 promote
TIM_USE_OUTPUT_AUTO pads to motors and claim whole timers as motor-only, silently removing
servo-capable outputs.
Agent Prompt 
## Issue description
`pwmEnsureEnoughtMotors()` pass 1 now uses `timerCounted[]` to avoid double-counting a physical timer, but it still relies on `motorOnlyOutputs++` plus `pwmClaimTimer()`'s **changed** count to represent the number of motor outputs on that timer. If all channels on a timer are already motor-only, `pwmClaimTimer()` returns 0, so the timer contributes only 1 to `motorOnlyOutputs` even if it has 2–4 motor pads.

This can leave `motorOnlyOutputs < motorCount` and cause pass 2 to promote `TIM_USE_OUTPUT_AUTO` pads to motors unnecessarily; because promotion calls `pwmClaimTimer()`, it can claim an entire unrelated timer as motor-only and those siblings will not be demoted later (they no longer match the pass-2 `!TIM_IS_MOTOR_ONLY(...)` guard).

## Issue Context
Example target with 4 motor pads on a single timer plus AUTO pads:
- `IFLIGHT_BLITZ_F7_AIO` has 4x `TIM_USE_MOTOR` on `TIM3` and additional `TIM_USE_OUTPUT_AUTO` on `TIM1`/`TIM4`, so after this change pass 1 counts the 4 TIM3 motors as **1**, potentially triggering pass-2 promotion of AUTO outputs.

## Fix Focus Areas
- src/main/drivers/pwm_mapping.c[260-317]
- src/main/target/IFLIGHT_BLITZ_F7_AIO/target.c[32-45]

## Suggested fix approach
When encountering the first motor-only pad for a physical timer (i.e., when `timerCounted[timerId]` is false), compute the number of usable pads for that timer and add that count once, instead of adding `1 + pwmClaimTimer(changed)`.

Concretely:
1. Compute `timerId = timer2id(timHw->tim)` once.
2. If motor-only and not yet counted:
   - Count pads that share `timHw->tim` (optionally excluding conflicts via `checkPwmTimerConflicts()` if the intent is “usable motor outputs”).
   - Add that pad-count to `motorOnlyOutputs`.
   - Call `pwmClaimTimer()` to sync flags, but do **not** use its return value for the motor output count.

This preserves de-duplication while keeping the counter accurate for timers where channels were already motor-only.

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

}
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