From a6db7d56ba808f07f14361443f540feeaef58675 Mon Sep 17 00:00:00 2001
From: Benjamin Valentin <benpicco@googlemail.com>
Date: Mon, 22 Jun 2020 00:22:35 +0200
Subject: [PATCH] drivers/at86rf215: fix CCA duration

The standard CCA backoff period is 8 symbols and only differs for
MR-O-QPSK where it is dependent on the chip rate.
---
 drivers/at86rf215/at86rf215_fsk.c              |  3 ++-
 drivers/at86rf215/at86rf215_o-qpsk.c           |  6 ++++--
 drivers/at86rf215/at86rf215_ofdm.c             |  5 +++--
 drivers/at86rf215/include/at86rf215_internal.h |  6 ------
 sys/include/net/ieee802154.h                   | 17 ++++++++++++++++-
 5 files changed, 25 insertions(+), 12 deletions(-)

diff --git a/drivers/at86rf215/at86rf215_fsk.c b/drivers/at86rf215/at86rf215_fsk.c
index fb5b48a4ab..863c082bc8 100644
--- a/drivers/at86rf215/at86rf215_fsk.c
+++ b/drivers/at86rf215/at86rf215_fsk.c
@@ -423,7 +423,8 @@ static void _set_ack_timeout(at86rf215_t *dev, bool mord4, bool fec)
 
 static void _set_csma_backoff_period(at86rf215_t *dev)
 {
-    dev->csma_backoff_period = AT86RF215_BACKOFF_PERIOD_IN_SYMBOLS * FSK_SYMBOL_TIME_US;
+    dev->csma_backoff_period = IEEE802154_CCA_DURATION_IN_SYMBOLS * FSK_SYMBOL_TIME_US
+                             + IEEE802154G_ATURNAROUNDTIME_US;
 
     DEBUG("[%s] CSMA BACKOFF: %"PRIu32" µs\n", "FSK", dev->csma_backoff_period);
 }
diff --git a/drivers/at86rf215/at86rf215_o-qpsk.c b/drivers/at86rf215/at86rf215_o-qpsk.c
index ca78acd8b1..88f3095c3f 100644
--- a/drivers/at86rf215/at86rf215_o-qpsk.c
+++ b/drivers/at86rf215/at86rf215_o-qpsk.c
@@ -314,13 +314,15 @@ static void _set_ack_timeout(at86rf215_t *dev, uint8_t chips, uint8_t mode)
 
 static inline void _set_csma_backoff_period(at86rf215_t *dev, uint8_t chips)
 {
-    dev->csma_backoff_period = AT86RF215_BACKOFF_PERIOD_IN_SYMBOLS * _get_symbol_duration_us(chips);
+    dev->csma_backoff_period = _get_cca_duration_syms(chips) * _get_symbol_duration_us(chips)
+                             + IEEE802154G_ATURNAROUNDTIME_US;
     DEBUG("[%s] CSMA BACKOFF: %"PRIu32" µs\n", "O-QPSK", dev->csma_backoff_period);
 }
 
 static inline void _set_csma_backoff_period_legacy(at86rf215_t *dev)
 {
-    dev->csma_backoff_period = AT86RF215_BACKOFF_PERIOD_IN_SYMBOLS * LEGACY_QPSK_SYMBOL_TIME_US;
+    dev->csma_backoff_period = (IEEE802154_ATURNAROUNDTIME_IN_SYMBOLS + IEEE802154_CCA_DURATION_IN_SYMBOLS)
+                             * LEGACY_QPSK_SYMBOL_TIME_US;
     DEBUG("[%s] CSMA BACKOFF: %"PRIu32" µs\n", "legacy O-QPSK", dev->csma_backoff_period);
 }
 
diff --git a/drivers/at86rf215/at86rf215_ofdm.c b/drivers/at86rf215/at86rf215_ofdm.c
index fdb101dde9..aaed4aed3f 100644
--- a/drivers/at86rf215/at86rf215_ofdm.c
+++ b/drivers/at86rf215/at86rf215_ofdm.c
@@ -268,8 +268,9 @@ int at86rf215_configure_OFDM(at86rf215_t *dev, uint8_t option, uint8_t scheme)
 
     at86rf215_reg_write(dev, dev->BBC->RG_OFDMPHRTX, scheme);
 
-    dev->csma_backoff_period = AT86RF215_BACKOFF_PERIOD_IN_SYMBOLS *
-                               OFDM_SYMBOL_TIME_US;
+    dev->csma_backoff_period = IEEE802154G_ATURNAROUNDTIME_US
+                             + IEEE802154_CCA_DURATION_IN_SYMBOLS
+                             * OFDM_SYMBOL_TIME_US;
     DEBUG("[%s] CSMA BACKOFF: %" PRIu32 " µs\n", "OFDM",
           dev->csma_backoff_period);
 
diff --git a/drivers/at86rf215/include/at86rf215_internal.h b/drivers/at86rf215/include/at86rf215_internal.h
index 39f849dae7..da2e1f3ac9 100644
--- a/drivers/at86rf215/include/at86rf215_internal.h
+++ b/drivers/at86rf215/include/at86rf215_internal.h
@@ -43,12 +43,6 @@ extern "C" {
 /** Default energy detect threshold for CSMA (reset value) */
 #define AT86RF215_EDT_DEFAULT           (-84) /* dBm */
 
-/**
- * This is used to calculate the csma backoff based on the bitrate.
- */
-/** 20 symbols is the std period length */
-#define AT86RF215_BACKOFF_PERIOD_IN_SYMBOLS (20U)
-
 /**
  * Default Parameters for 802.15.4 retransmissions & CSMA
  * @{
diff --git a/sys/include/net/ieee802154.h b/sys/include/net/ieee802154.h
index 11bc3b1257..607daa84fe 100644
--- a/sys/include/net/ieee802154.h
+++ b/sys/include/net/ieee802154.h
@@ -111,7 +111,22 @@ extern "C" {
  *
  * 802.15.4g, Table 70 (p. 43)
  */
-#define IEEE802154G_ATURNAROUNDTIME_US (1 * US_PER_MS)
+#define IEEE802154G_ATURNAROUNDTIME_US          (1 * US_PER_MS)
+
+/**
+ * IEEE Std 802.15.4-2020
+ * Table 11-1—PHY constants: The value is 12 for all other PHYs.
+ */
+#define IEEE802154_ATURNAROUNDTIME_IN_SYMBOLS   (12)
+
+/**
+ * IEEE Std 802.15.4-2020
+ * Table 11-1—PHY constants: For all other PHYs¹, the duration of
+ * 8 symbol periods.
+ *
+ * [1] all but MR-O-QPSK
+ */
+#define IEEE802154_CCA_DURATION_IN_SYMBOLS      (8)
 
 /**
  * @brief   802.15.4 PHY modes