at86rf230: add support for calibration timeout

This patch adds a handling for calibration if we are 5 minutes in PLL
state. I first tried to implement the calibration functionality in
TX_ON state via register values CF_START and DCU_START, but this occurs
a one second delay at each calibration time.

An another solution to start a calibration is to switch from TRX_OFF
state into TX_ON, then a calibration is done automatically by
transceiver. This method will be used in this patch, after each transmit
of a frame we check with jiffies if the PLL is set 5 minutes without
doing a TRX_OFF->(TX_ON || RX_AACK_ON) or channel switch. The worst case
would be a transceiver in receiving mode only, but this is under normal
operation very unlikely.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Cc: Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
Cc: Werner Almesberger <werner@almesberger.net>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

1 files changed, 58 insertions, 14 deletions

diff --git a/drivers/net/ieee802154/at86rf230.c b/drivers/net/ieee802154/at86rf230.c
index 4030fa69f176..795106c23097 100644
--- a/drivers/net/ieee802154/at86rf230.c
+++ b/drivers/net/ieee802154/at86rf230.c
@@ -20,6 +20,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/hrtimer.h>
+#include <linux/jiffies.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/gpio.h>
@@ -60,6 +61,8 @@ struct at86rf2xx_chip_data {
  * We assume the max_frame_retries (7) value of 802.15.4 here.
  */
 #define AT86RF2XX_MAX_TX_RETRIES        7
+/* We use the recommended 5 minutes timeout to recalibrate */
+#define AT86RF2XX_CAL_LOOP_TIMEOUT      (5 * 60 * HZ)
 
 struct at86rf230_state_change {
         struct at86rf230_local *lp;
@@ -90,6 +93,7 @@ struct at86rf230_local {
         struct at86rf230_state_change irq;
 
         bool tx_aret;
+        unsigned long cal_timeout;
         s8 max_frame_retries;
         bool is_tx;
         /* spinlock for is_tx protection */
@@ -491,6 +495,14 @@ at86rf230_async_read_reg(struct at86rf230_local *lp, const u8 reg,
         }
 }
 
+static inline u8 at86rf230_state_to_force(u8 state)
+{
+        if (state == STATE_TX_ON)
+                return STATE_FORCE_TX_ON;
+        else
+                return STATE_FORCE_TRX_OFF;
+}
+
 static void
 at86rf230_async_state_assert(void *context)
 {
@@ -527,11 +539,12 @@ at86rf230_async_state_assert(void *context)
                          * higher or equal than AT86RF2XX_MAX_TX_RETRIES we
                          * will do a force change.
                          */
-                        if (ctx->to_state == STATE_TX_ON) {
-                                u8 state = STATE_TX_ON;
+                        if (ctx->to_state == STATE_TX_ON ||
+                            ctx->to_state == STATE_TRX_OFF) {
+                                u8 state = ctx->to_state;
 
                                 if (lp->tx_retry >= AT86RF2XX_MAX_TX_RETRIES)
-                                        state = STATE_FORCE_TX_ON;
+                                        state = at86rf230_state_to_force(state);
                                 lp->tx_retry++;
 
                                 at86rf230_async_state_change(lp, ctx, state,
@@ -599,6 +612,11 @@ at86rf230_async_state_delay(void *context)
                         goto change;
                 case STATE_TX_ON:
                         tim = ktime_set(0, c->t_off_to_tx_on * NSEC_PER_USEC);
+                        /* state change from TRX_OFF to TX_ON to do a
+                         * calibration, we need to reset the timeout for the
+                         * next one.
+                         */
+                        lp->cal_timeout = jiffies + AT86RF2XX_CAL_LOOP_TIMEOUT;
                         goto change;
                 default:
                         break;
@@ -606,10 +624,11 @@ at86rf230_async_state_delay(void *context)
                 break;
         case STATE_BUSY_RX_AACK:
                 switch (ctx->to_state) {
+                case STATE_TRX_OFF:
                 case STATE_TX_ON:
                         /* Wait for worst case receiving time if we
                          * didn't make a force change from BUSY_RX_AACK
-                         * to TX_ON.
+                         * to TX_ON or TRX_OFF.
                          */
                         if (!force) {
                                 tim = ktime_set(0, (c->t_frame + c->t_p_ack) *
@@ -969,25 +988,45 @@ at86rf230_xmit_tx_on(void *context)
                                      at86rf230_write_frame, false);
 }
 
-static int
-at86rf230_xmit(struct ieee802154_hw *hw, struct sk_buff *skb)
+static void
+at86rf230_xmit_start(void *context)
 {
-        struct at86rf230_local *lp = hw->priv;
-        struct at86rf230_state_change *ctx = &lp->tx;
-
-        void (*tx_complete)(void *context) = at86rf230_write_frame;
-
-        lp->tx_skb = skb;
+        struct at86rf230_state_change *ctx = context;
+        struct at86rf230_local *lp = ctx->lp;
 
         /* In ARET mode we need to go into STATE_TX_ARET_ON after we
          * are in STATE_TX_ON. The pfad differs here, so we change
          * the complete handler.
          */
         if (lp->tx_aret)
-                tx_complete = at86rf230_xmit_tx_on;
+                at86rf230_async_state_change(lp, ctx, STATE_TX_ON,
+                                             at86rf230_xmit_tx_on, false);
+        else
+                at86rf230_async_state_change(lp, ctx, STATE_TX_ON,
+                                             at86rf230_write_frame, false);
+}
+
+static int
+at86rf230_xmit(struct ieee802154_hw *hw, struct sk_buff *skb)
+{
+        struct at86rf230_local *lp = hw->priv;
+        struct at86rf230_state_change *ctx = &lp->tx;
 
+        lp->tx_skb = skb;
         lp->tx_retry = 0;
-        at86rf230_async_state_change(lp, ctx, STATE_TX_ON, tx_complete, false);
+
+        /* After 5 minutes in PLL and the same frequency we run again the
+         * calibration loops which is recommended by at86rf2xx datasheets.
+         *
+         * The calibration is initiate by a state change from TRX_OFF
+         * to TX_ON, the lp->cal_timeout should be reinit by state_delay
+         * function then to start in the next 5 minutes.
+         */
+        if (time_is_before_jiffies(lp->cal_timeout))
+                at86rf230_async_state_change(lp, ctx, STATE_TRX_OFF,
+                                             at86rf230_xmit_start, false);
+        else
+                at86rf230_xmit_start(ctx);
 
         return 0;
 }
@@ -1003,6 +1042,9 @@ at86rf230_ed(struct ieee802154_hw *hw, u8 *level)
 static int
 at86rf230_start(struct ieee802154_hw *hw)
 {
+        struct at86rf230_local *lp = hw->priv;
+
+        lp->cal_timeout = jiffies + AT86RF2XX_CAL_LOOP_TIMEOUT;
         return at86rf230_sync_state_change(hw->priv, STATE_RX_AACK_ON);
 }
 
@@ -1083,6 +1125,8 @@ at86rf230_channel(struct ieee802154_hw *hw, u8 page, u8 channel)
         /* Wait for PLL */
         usleep_range(lp->data->t_channel_switch,
                      lp->data->t_channel_switch + 10);
+
+        lp->cal_timeout = jiffies + AT86RF2XX_CAL_LOOP_TIMEOUT;
         return rc;
 }