diff --git a/examples/platforms/nrf528xx/src/radio.c b/examples/platforms/nrf528xx/src/radio.c
index 31c17d5c2..172103317 100644
--- a/examples/platforms/nrf528xx/src/radio.c
+++ b/examples/platforms/nrf528xx/src/radio.c
@@ -472,8 +472,6 @@ otError otPlatRadioTransmit(otInstance *aInstance, otRadioFrame *aFrame)
         nrf5FemEnable();
     }
 
-    nrf_802154_channel_set(aFrame->mChannel);
-
 #if OPENTHREAD_CONFIG_THREAD_VERSION >= OT_THREAD_VERSION_1_2
     if (aFrame->mInfo.mTxInfo.mTxDelay != 0)
     {
@@ -486,6 +484,8 @@ otError otPlatRadioTransmit(otInstance *aInstance, otRadioFrame *aFrame)
     else
 #endif
     {
+        nrf_802154_channel_set(aFrame->mChannel);
+
         if (aFrame->mInfo.mTxInfo.mCsmaCaEnabled)
         {
             nrf_802154_transmit_csma_ca_raw(&aFrame->mPsdu[-1]);
diff --git a/src/core/mac/sub_mac.hpp b/src/core/mac/sub_mac.hpp
index b2c1c8ec0..b2036e3a5 100644
--- a/src/core/mac/sub_mac.hpp
+++ b/src/core/mac/sub_mac.hpp
@@ -532,8 +532,8 @@ private:
 
 #if OPENTHREAD_CONFIG_MAC_CSL_RECEIVER_ENABLE
     enum : uint32_t{
-        kCslSampleWindow =
-            OPENTHREAD_CONFIG_CSL_SAMPLE_WINDOW * kUsPerTenSymbols, ///< The SSED sample window in units of 10 symbols.
+        kCslSampleWindow = OPENTHREAD_CONFIG_CSL_SAMPLE_WINDOW *
+                           kUsPerTenSymbols, ///< The SSED sample window in units of microseconds.
         kCslReceiveTimeAhead =
             OPENTHREAD_CONFIG_CSL_RECEIVE_TIME_AHEAD, ///< CSL receivers would wake up `kCslReceiveTimeAhead` earlier
                                                       ///< than expected sample window. The time is in unit of 10
diff --git a/src/core/thread/csl_tx_scheduler.cpp b/src/core/thread/csl_tx_scheduler.cpp
index d81385d68..613003e93 100644
--- a/src/core/thread/csl_tx_scheduler.cpp
+++ b/src/core/thread/csl_tx_scheduler.cpp
@@ -119,7 +119,6 @@ void CslTxScheduler::Clear(void)
  */
 void CslTxScheduler::RescheduleCslTx(void)
 {
-    uint64_t radioNow     = otPlatRadioGetNow(&GetInstance());
     uint32_t minDelayTime = Time::kMaxDuration;
     Child *  bestChild    = nullptr;
 
@@ -133,7 +132,7 @@ void CslTxScheduler::RescheduleCslTx(void)
             continue;
         }
 
-        delay = GetNextCslTransmissionDelay(child, radioNow, cslTxDelay);
+        delay = GetNextCslTransmissionDelay(child, cslTxDelay);
 
         if (delay < minDelayTime)
         {
@@ -150,19 +149,18 @@ void CslTxScheduler::RescheduleCslTx(void)
     mCslTxChild = bestChild;
 }
 
-uint32_t CslTxScheduler::GetNextCslTransmissionDelay(const Child &aChild,
-                                                     uint64_t     aRadioNow,
-                                                     uint32_t &   aDelayFromLastRx) const
+uint32_t CslTxScheduler::GetNextCslTransmissionDelay(const Child &aChild, uint32_t &aDelayFromLastRx) const
 {
+    uint64_t radioNow      = otPlatRadioGetNow(&GetInstance());
     uint32_t periodInUs    = aChild.GetCslPeriod() * kUsPerTenSymbols;
     uint64_t firstTxWindow = aChild.GetLastRxTimestamp() + aChild.GetCslPhase() * kUsPerTenSymbols;
-    uint64_t nextTxWindow  = aRadioNow - (aRadioNow % periodInUs) + (firstTxWindow % periodInUs);
+    uint64_t nextTxWindow  = radioNow - (radioNow % periodInUs) + (firstTxWindow % periodInUs);
 
-    while (aRadioNow + mCslFrameRequestAheadUs >= nextTxWindow) nextTxWindow += periodInUs;
+    while (nextTxWindow < radioNow + mCslFrameRequestAheadUs) nextTxWindow += periodInUs;
 
     aDelayFromLastRx = static_cast<uint32_t>(nextTxWindow - aChild.GetLastRxTimestamp());
 
-    return static_cast<uint32_t>(nextTxWindow - aRadioNow - mCslFrameRequestAheadUs);
+    return static_cast<uint32_t>(nextTxWindow - radioNow - mCslFrameRequestAheadUs);
 }
 
 Mac::TxFrame *CslTxScheduler::HandleFrameRequest(Mac::TxFrames &aTxFrames)
@@ -207,7 +205,8 @@ Mac::TxFrame *CslTxScheduler::HandleFrameRequest(Mac::TxFrames &aTxFrames)
 
     frame->SetChannel(mCslTxChild->GetCslChannel() == 0 ? Get<Mac::Mac>().GetPanChannel()
                                                         : mCslTxChild->GetCslChannel());
-    GetNextCslTransmissionDelay(*mCslTxChild, otPlatRadioGetNow(&GetInstance()), txDelay);
+
+    GetNextCslTransmissionDelay(*mCslTxChild, txDelay);
     frame->SetTxDelay(txDelay);
     frame->SetTxDelayBaseTime(
         static_cast<uint32_t>(mCslTxChild->GetLastRxTimestamp())); // Only LSB part of the time is required.
diff --git a/src/core/thread/csl_tx_scheduler.hpp b/src/core/thread/csl_tx_scheduler.hpp
index 319c59881..645315c63 100644
--- a/src/core/thread/csl_tx_scheduler.hpp
+++ b/src/core/thread/csl_tx_scheduler.hpp
@@ -193,7 +193,7 @@ private:
     void InitFrameRequestAhead(void);
     void RescheduleCslTx(void);
 
-    uint32_t GetNextCslTransmissionDelay(const Child &aChild, uint64_t aRadioNow, uint32_t &aDelayFromLastRx) const;
+    uint32_t GetNextCslTransmissionDelay(const Child &aChild, uint32_t &aDelayFromLastRx) const;
 
     // Callbacks from `Mac`
     Mac::TxFrame *HandleFrameRequest(Mac::TxFrames &aTxFrames);