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From:   Ping-Ke Shih <pkshih@realtek.com>
To:     <kvalo@kernel.org>
CC:     <kevin_yang@realtek.com>, <linux-wireless@vger.kernel.org>
Subject: [PATCH 3/6] wifi: rtw89: introduce helpers to wait/complete on condition
Date:   Fri, 18 Nov 2022 13:10:39 +0800
Message-ID: <20221118051042.29968-4-pkshih@realtek.com>
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From: Zong-Zhe Yang <kevin_yang@realtek.com>

MCC (multi-channel concurrency) related H2Cs require to wait for C2H
responses to judge the execution result and data. We introduce helpers
to assist this process. Besides, we would like the helpers to be generic
for use in driver even outside of MCC H2C/C2H, so we make a independent
patch for them.

In the following, I describe the things first.
```
(A)	C2H is generated by FW, and then transferred upto driver. Hence,
	driver cannot get it immediately without a bit waitting/blocking.
	For this, we choose to use wait_for_completion_*() instead of
	busy polling.
(B)	From the driver management perspective, a scenario, e.g. MCC,
	may have mulitple kind of H2C functions requiring this process
	to wait for corresponding C2Hs. But, the driver management flow
	uses mutex to protect each behavior. So, one scenario triggers
	one H2C function at one time. To avoid rampant instances of
	struct completion for each H2C function, we choose to use one
	struct completion with one condition flag for one scenario.
(C)	C2Hs, which H2Cs will be waitting for, cannot be ordered with
	driver management flow, i.e. cannot enqueue work to the same
	ordered workqueue and cannot lock by the same mutex, to prevent
	H2C side from getting no C2H responses. So, those C2Hs are parsed
	in interrupt context directly as done in previous commit.
(D)	Following (C), the above underline H2Cs and C2Hs will be handled
	in different contexts without sync. So, we use atomic_cmpxchg()
	to compare and change the condition in atomic.
```

So, we introduce struct rtw89_wait_info which combines struct completion
and atomic_t. Then, the below are the descriptions for helper functions.
* rtw89_wait_for_cond() to wait for a completion based on a condition.
* rtw89_complete_cond() to complete a given condition and carry data.
Each rtw89_wait_info instance independently determines the meaning of
its waitting conditions. But, RTW89_WAIT_COND_IDLE (UINT_MAX) is reserved.

Signed-off-by: Zong-Zhe Yang <kevin_yang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
---
 drivers/net/wireless/realtek/rtw89/core.c | 35 +++++++++++++++++++++++
 drivers/net/wireless/realtek/rtw89/core.h | 31 ++++++++++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/drivers/net/wireless/realtek/rtw89/core.c b/drivers/net/wireless/realtek/rtw89/core.c
index f30aadc41f2be..e0b044a33207a 100644
--- a/drivers/net/wireless/realtek/rtw89/core.c
+++ b/drivers/net/wireless/realtek/rtw89/core.c
@@ -2941,6 +2941,41 @@ void rtw89_core_update_beacon_work(struct work_struct *work)
 	mutex_unlock(&rtwdev->mutex);
 }
 
+int rtw89_wait_for_cond(struct rtw89_wait_info *wait, unsigned int cond)
+{
+	struct completion *cmpl = &wait->completion;
+	unsigned long timeout;
+	unsigned int cur;
+
+	cur = atomic_cmpxchg(&wait->cond, RTW89_WAIT_COND_IDLE, cond);
+	if (cur != RTW89_WAIT_COND_IDLE)
+		return -EBUSY;
+
+	timeout = wait_for_completion_timeout(cmpl, RTW89_WAIT_FOR_COND_TIMEOUT);
+	if (timeout == 0) {
+		atomic_set(&wait->cond, RTW89_WAIT_COND_IDLE);
+		return -ETIMEDOUT;
+	}
+
+	if (wait->data.err)
+		return -EFAULT;
+
+	return 0;
+}
+
+void rtw89_complete_cond(struct rtw89_wait_info *wait, unsigned int cond,
+			 const struct rtw89_completion_data *data)
+{
+	unsigned int cur;
+
+	cur = atomic_cmpxchg(&wait->cond, cond, RTW89_WAIT_COND_IDLE);
+	if (cur != cond)
+		return;
+
+	wait->data = *data;
+	complete(&wait->completion);
+}
+
 int rtw89_core_start(struct rtw89_dev *rtwdev)
 {
 	int ret;
diff --git a/drivers/net/wireless/realtek/rtw89/core.h b/drivers/net/wireless/realtek/rtw89/core.h
index 3fff666c0e84a..5a7d5514bba9a 100644
--- a/drivers/net/wireless/realtek/rtw89/core.h
+++ b/drivers/net/wireless/realtek/rtw89/core.h
@@ -2802,6 +2802,34 @@ struct rtw89_mac_info {
 	u8 cpwm_seq_num;
 };
 
+struct rtw89_completion_data {
+	bool err;
+#define RTW89_COMPLETION_BUF_SIZE 24
+	u8 buf[RTW89_COMPLETION_BUF_SIZE];
+};
+
+#define rtw89_completion_cast(cmpl_data, ptr)				\
+({									\
+	typecheck(struct rtw89_completion_data *, cmpl_data);		\
+	BUILD_BUG_ON(sizeof(*(ptr)) > RTW89_COMPLETION_BUF_SIZE);	\
+	(typeof(ptr))(cmpl_data)->buf;					\
+})
+
+struct rtw89_wait_info {
+#define RTW89_WAIT_COND_IDLE UINT_MAX
+	atomic_t cond;
+	struct completion completion;
+	struct rtw89_completion_data data;
+};
+
+#define RTW89_WAIT_FOR_COND_TIMEOUT msecs_to_jiffies(100)
+
+static inline void rtw89_init_wait(struct rtw89_wait_info *wait)
+{
+	init_completion(&wait->completion);
+	atomic_set(&wait->cond, RTW89_WAIT_COND_IDLE);
+}
+
 enum rtw89_fw_type {
 	RTW89_FW_NORMAL = 1,
 	RTW89_FW_WOWLAN = 3,
@@ -4440,6 +4468,9 @@ int rtw89_regd_init(struct rtw89_dev *rtwdev,
 void rtw89_regd_notifier(struct wiphy *wiphy, struct regulatory_request *request);
 void rtw89_traffic_stats_init(struct rtw89_dev *rtwdev,
 			      struct rtw89_traffic_stats *stats);
+int rtw89_wait_for_cond(struct rtw89_wait_info *wait, unsigned int cond);
+void rtw89_complete_cond(struct rtw89_wait_info *wait, unsigned int cond,
+			 const struct rtw89_completion_data *data);
 int rtw89_core_start(struct rtw89_dev *rtwdev);
 void rtw89_core_stop(struct rtw89_dev *rtwdev);
 void rtw89_core_update_beacon_work(struct work_struct *work);
-- 
2.25.1