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

From: Kalle Valo <[email-masked]>
Date: Thu, 28 Oct 2021 10:28:19 +0300

Bryan O'Donoghue <[email-masked]> writes:

> 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 <[email-masked]>
>> ---
>>   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 <[email-masked]>

Thanks, all review and testing is very much appreciated. But please trim
your replies, including the whole patch makes reading your replies and
using patchwork much harder:

https://patchwork.kernel.org/project/linux-wireless/patch/[email-masked]/

I recommend just including the commit log and dropping the rest.

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