Re: [PATCH v2 3/3] wcn36xx: ensure pairing of init_scan/finish_scan and start_scan/end_scan

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On 27/10/2021 18:03, Benjamin Li wrote:
An SMD capture from the downstream prima driver on WCN3680B shows the
following command sequence for connected scans:

- init_scan_req
     - start_scan_req, channel 1
     - end_scan_req, channel 1
     - start_scan_req, channel 2
     - ...
     - end_scan_req, channel 3
- finish_scan_req
- init_scan_req
     - start_scan_req, channel 4
     - ...
     - end_scan_req, channel 6
- finish_scan_req
- ...
     - end_scan_req, channel 165
- finish_scan_req

Upstream currently never calls wcn36xx_smd_end_scan, and in some cases[1]
still sends finish_scan_req twice in a row or before init_scan_req. A
typical connected scan looks like this:

- init_scan_req
     - start_scan_req, channel 1
- finish_scan_req
- init_scan_req
     - start_scan_req, channel 2
- ...
     - start_scan_req, channel 165
- finish_scan_req
- finish_scan_req

This patch cleans up scanning so that init/finish and start/end are always
paired together and correctly nested.

- init_scan_req
     - start_scan_req, channel 1
     - end_scan_req, channel 1
- finish_scan_req
- init_scan_req
     - start_scan_req, channel 2
     - end_scan_req, channel 2
- ...
     - start_scan_req, channel 165
     - end_scan_req, channel 165
- finish_scan_req

Note that upstream will not do batching of 3 active-probe scans before
returning to the operating channel, and this patch does not change that.
To match downstream in this aspect, adjust IEEE80211_PROBE_DELAY and/or
the 125ms max off-channel time in ieee80211_scan_state_decision.

[1]: commit d195d7aac09b ("wcn36xx: Ensure finish scan is not requested
before start scan") addressed one case of finish_scan_req being sent
without a preceding init_scan_req (the case of the operating channel
coinciding with the first scan channel); two other cases are:
1) if SW scan is started and aborted immediately, without scanning any
    channels, we send a finish_scan_req without ever sending init_scan_req,
    and
2) as SW scan logic always returns us to the operating channel before
    calling wcn36xx_sw_scan_complete, finish_scan_req is always sent twice
    at the end of a SW scan

Fixes: 8e84c2582169 ("wcn36xx: mac80211 driver for Qualcomm WCN3660/WCN3680 hardware")
Signed-off-by: Benjamin Li <benl@xxxxxxxxxxxx>
---
  drivers/net/wireless/ath/wcn36xx/main.c    | 34 +++++++++++++++++-----
  drivers/net/wireless/ath/wcn36xx/smd.c     |  4 +++
  drivers/net/wireless/ath/wcn36xx/wcn36xx.h |  1 +
  3 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/drivers/net/wireless/ath/wcn36xx/main.c b/drivers/net/wireless/ath/wcn36xx/main.c
index 18383d0fc0933..37b4016f020c9 100644
--- a/drivers/net/wireless/ath/wcn36xx/main.c
+++ b/drivers/net/wireless/ath/wcn36xx/main.c
@@ -400,6 +400,7 @@ static void wcn36xx_change_opchannel(struct wcn36xx *wcn, int ch)
  static int wcn36xx_config(struct ieee80211_hw *hw, u32 changed)
  {
  	struct wcn36xx *wcn = hw->priv;
+	int ret;
wcn36xx_dbg(WCN36XX_DBG_MAC, "mac config changed 0x%08x\n", changed); @@ -415,17 +416,31 @@ static int wcn36xx_config(struct ieee80211_hw *hw, u32 changed)
  			 * want to receive/transmit regular data packets, then
  			 * simply stop the scan session and exit PS mode.
  			 */
-			wcn36xx_smd_finish_scan(wcn, HAL_SYS_MODE_SCAN,
-						wcn->sw_scan_vif);
-			wcn->sw_scan_channel = 0;
+			if (wcn->sw_scan_channel)
+				wcn36xx_smd_end_scan(wcn, wcn->sw_scan_channel);
+			if (wcn->sw_scan_init) {
+				wcn36xx_smd_finish_scan(wcn, HAL_SYS_MODE_SCAN,
+							wcn->sw_scan_vif);
+			}
  		} else if (wcn->sw_scan) {
  			/* A scan is ongoing, do not change the operating
  			 * channel, but start a scan session on the channel.
  			 */
-			wcn36xx_smd_init_scan(wcn, HAL_SYS_MODE_SCAN,
-					      wcn->sw_scan_vif);
+			if (wcn->sw_scan_channel)
+				wcn36xx_smd_end_scan(wcn, wcn->sw_scan_channel);
+			if (!wcn->sw_scan_init) {
+				/* This can fail if we are unable to notify the
+				 * operating channel.
+				 */
+				ret = wcn36xx_smd_init_scan(wcn,
+							    HAL_SYS_MODE_SCAN,
+							    wcn->sw_scan_vif);
+				if (ret) {
+					mutex_unlock(&wcn->conf_mutex);
+					return -EIO;
+				}
+			}
  			wcn36xx_smd_start_scan(wcn, ch);
-			wcn->sw_scan_channel = ch;
  		} else {
  			wcn36xx_change_opchannel(wcn, ch);
  		}
@@ -723,7 +738,12 @@ static void wcn36xx_sw_scan_complete(struct ieee80211_hw *hw,
  	wcn36xx_dbg(WCN36XX_DBG_MAC, "sw_scan_complete");
/* ensure that any scan session is finished */
-	wcn36xx_smd_finish_scan(wcn, HAL_SYS_MODE_SCAN, wcn->sw_scan_vif);
+	if (wcn->sw_scan_channel)
+		wcn36xx_smd_end_scan(wcn, wcn->sw_scan_channel);
+	if (wcn->sw_scan_init) {
+		wcn36xx_smd_finish_scan(wcn, HAL_SYS_MODE_SCAN,
+					wcn->sw_scan_vif);
+	}
  	wcn->sw_scan = false;
  	wcn->sw_scan_opchannel = 0;
  }
diff --git a/drivers/net/wireless/ath/wcn36xx/smd.c b/drivers/net/wireless/ath/wcn36xx/smd.c
index 3cecc8f9c9647..830341be72673 100644
--- a/drivers/net/wireless/ath/wcn36xx/smd.c
+++ b/drivers/net/wireless/ath/wcn36xx/smd.c
@@ -721,6 +721,7 @@ int wcn36xx_smd_init_scan(struct wcn36xx *wcn, enum wcn36xx_hal_sys_mode mode,
  		wcn36xx_err("hal_init_scan response failed err=%d\n", ret);
  		goto out;
  	}
+	wcn->sw_scan_init = true;
  out:
  	mutex_unlock(&wcn->hal_mutex);
  	return ret;
@@ -751,6 +752,7 @@ int wcn36xx_smd_start_scan(struct wcn36xx *wcn, u8 scan_channel)
  		wcn36xx_err("hal_start_scan response failed err=%d\n", ret);
  		goto out;
  	}
+	wcn->sw_scan_channel = scan_channel;
  out:
  	mutex_unlock(&wcn->hal_mutex);
  	return ret;
@@ -781,6 +783,7 @@ int wcn36xx_smd_end_scan(struct wcn36xx *wcn, u8 scan_channel)
  		wcn36xx_err("hal_end_scan response failed err=%d\n", ret);
  		goto out;
  	}
+	wcn->sw_scan_channel = 0;
  out:
  	mutex_unlock(&wcn->hal_mutex);
  	return ret;
@@ -822,6 +825,7 @@ int wcn36xx_smd_finish_scan(struct wcn36xx *wcn,
  		wcn36xx_err("hal_finish_scan response failed err=%d\n", ret);
  		goto out;
  	}
+	wcn->sw_scan_init = false;
  out:
  	mutex_unlock(&wcn->hal_mutex);
  	return ret;
diff --git a/drivers/net/wireless/ath/wcn36xx/wcn36xx.h b/drivers/net/wireless/ath/wcn36xx/wcn36xx.h
index 1c8d918137da2..fbd0558c2c196 100644
--- a/drivers/net/wireless/ath/wcn36xx/wcn36xx.h
+++ b/drivers/net/wireless/ath/wcn36xx/wcn36xx.h
@@ -248,6 +248,7 @@ struct wcn36xx {
  	struct cfg80211_scan_request *scan_req;
  	bool			sw_scan;
  	u8			sw_scan_opchannel;
+	bool			sw_scan_init;
  	u8			sw_scan_channel;
  	struct ieee80211_vif	*sw_scan_vif;
  	struct mutex		scan_lock;


LGTM

Tested-by: Bryan O'Donoghue <bryan.odonoghue@xxxxxxxxxx>



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