wifi: rtw88: rtw8822c: refactor DAC IQ calibration to s32

PATCH Superseded Arsenii Pashchenko 2 participants 6 messages Aug 13 Realtek wireless driver (rtw88)

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Arsenii Pashchenko

author

2026-08-13 05:47 UTC #0 lore raw

v2 cover wifi: rtw88: rtw8822c: refactor DAC IQ calibration to s32

This series refactors the Digital-to-Analog Converter (DAC) IQ calibration routines in the rtw8822c driver.

The original code heavily relies on unsigned 32-bit math mapped over a 10-bit circular hardware register scale centered around 0x200. This introduces complex nested boundary checks, custom bubble sort rules, and custom min/max tracking helpers.

By migrating the temporary stack arrays and signatures to signed s32 and utilizing the kernel's sign_extend32() API, the coordination system is linearized. This allows the removal of internal custom helpers and collapses unsigned wrap-around logic into standard linear operations.

The series is broken down as follows:
Patch 1: Prepares signatures and stack buffers, converting types to s32. Patch 2: Introduces sign_extend32() and simplifies the validation window. Patch 3: Replaces custom bubble sort with the kernel's native sort(). Patch 4: Eliminates minmax_cmp, streamlining search and offset loops.

AI Disclosure:
An AI assistant was used for source code analysis and conceptual consultation regarding the signed math transformation. All code modifications, final implementations, and refactoring steps were written, reviewed, and verified manually by the author.

Testing:
- Every patch in the series was verified with scripts/checkpatch.pl and yielded 0 errors and 0 warnings.
- Each patch was sequentially built (bisected and compiled) to ensure there are no compiler warnings, pointer type mismatches, or broken builds at any intermediate step.
---
Changes in v2:
- Fixed missing target tree name in the subject prefix (switched to wireless-next).

Arsenii Pashchenko (4):
wifi: rtw88: rtw8822c: convert DAC IQ buffers and signatures to s32
wifi: rtw88: rtw8822c: use sign_extend32 for DAC IQ validation
wifi: rtw88: rtw8822c: switch to the kernel's sort() library
wifi: rtw88: rtw8822c: simplify amplitude search and offset via s32

 drivers/net/wireless/realtek/rtw88/rtw8822c.c | 146 ++++++------------
 1 file changed, 43 insertions(+), 103 deletions(-)

Signature · 1 line

2.55.0

Arsenii Pashchenko

author

2026-08-13 05:48 UTC #1 lore raw

PATCH v2 1/4 wifi: rtw88: rtw8822c: convert DAC IQ buffers and signatures to s32

Prepare the DAC IQ calibration path for signed math by converting the temporary stack arrays 'iv' and 'qv' from u32 to s32. Update all internal function signatures to accept s32 pointers.

To guarantee bisectability, wrap the existing unsigned logic in temporary casts to u32. This maintains identical mathematical behavior and avoids any compiler sign-compare warnings.

Signed-off-by Arsenii Pashchenko <[email protected]>

---
 drivers/net/wireless/realtek/rtw88/rtw8822c.c | 49 +++++++++++--------
 1 file changed, 28 insertions(+), 21 deletions(-)

drivers/net/wireless/realtek/rtw88/rtw8822c.c +28 ~~-21~~

index 244c80264..896e3e7b9 100644
@@ -153,9 +153,12 @@ static void rtw8822c_dac_restore_reg(struct rtw_dev *rtwdev,
 	}
 }
 
-static void rtw8822c_rf_minmax_cmp(struct rtw_dev *rtwdev, u32 value,
-				   u32 *min, u32 *max)
+static void rtw8822c_rf_minmax_cmp(struct rtw_dev *rtwdev, s32 value_s32,
+				   s32 *min_s32, s32 *max_s32)
 {
+	u32 value = (u32)value_s32;
+	u32 *min = (u32 *)min_s32;
+	u32 *max = (u32 *)max_s32;
 	if (value >= 0x200) {
 		if (*min >= 0x200) {
 			if (*min > value)

@@ -182,8 +185,10 @@ static void rtw8822c_rf_minmax_cmp(struct rtw_dev *rtwdev, u32 value,
 	}
 }
 
-static void __rtw8822c_dac_iq_sort(struct rtw_dev *rtwdev, u32 *v1, u32 *v2)
+static void __rtw8822c_dac_iq_sort(struct rtw_dev *rtwdev, s32 *v1_s32, s32 *v2_s32)
 {
+	u32 *v1 = (u32 *)v1_s32;
+	u32 *v2 = (u32 *)v2_s32;
 	if (*v1 >= 0x200 && *v2 >= 0x200) {
 		if (*v1 > *v2)
 			swap(*v1, *v2);

@@ -195,7 +200,7 @@ static void __rtw8822c_dac_iq_sort(struct rtw_dev *rtwdev, u32 *v1, u32 *v2)
 	}
 }
 
-static void rtw8822c_dac_iq_sort(struct rtw_dev *rtwdev, u32 *iv, u32 *qv)
+static void rtw8822c_dac_iq_sort(struct rtw_dev *rtwdev, s32 *iv, s32 *qv)
 {
 	u32 i, j;

@@ -207,8 +212,9 @@ static void rtw8822c_dac_iq_sort(struct rtw_dev *rtwdev, u32 *iv, u32 *qv)
 	}
 }
 
-static void rtw8822c_dac_iq_offset(struct rtw_dev *rtwdev, u32 *vec, u32 *val)
+static void rtw8822c_dac_iq_offset(struct rtw_dev *rtwdev, s32 *vec_s32, u32 *val)
 {
+	u32 *vec = (u32 *)vec_s32;
 	u32 p, m, t, i;
 
 	m = 0;

@@ -271,8 +277,9 @@ static u32 rtw8822c_get_path_read_addr(u8 path)
 	return base_addr;
 }
 
-static bool rtw8822c_dac_iq_check(struct rtw_dev *rtwdev, u32 value)
+static bool rtw8822c_dac_iq_check(struct rtw_dev *rtwdev, s32 value_s32)
 {
+	u32 value = (u32)value_s32;
 	bool ret = true;
 
 	if ((value >= 0x200 && (0x400 - value) > 0x64) ||

@@ -284,7 +291,7 @@ static bool rtw8822c_dac_iq_check(struct rtw_dev *rtwdev, u32 value)
 	return ret;
 }
 
-static void rtw8822c_dac_cal_iq_sample(struct rtw_dev *rtwdev, u32 *iv, u32 *qv)
+static void rtw8822c_dac_cal_iq_sample(struct rtw_dev *rtwdev, s32 *iv, s32 *qv)
 {
 	u32 temp;
 	int i = 0, cnt = 0;

@@ -292,8 +299,8 @@ static void rtw8822c_dac_cal_iq_sample(struct rtw_dev *rtwdev, u32 *iv, u32 *qv)
 	while (i < DACK_SN_8822C && cnt < 10000) {
 		cnt++;
 		temp = rtw_read32_mask(rtwdev, 0x2dbc, 0x3fffff);
-		iv[i] = (temp & 0x3ff000) >> 12;
-		qv[i] = temp & 0x3ff;
+		iv[i] = (s32)((temp & 0x3ff000) >> 12);
+		qv[i] = (s32)(temp & 0x3ff);
 
 		if (rtw8822c_dac_iq_check(rtwdev, iv[i]) &&
 		    rtw8822c_dac_iq_check(rtwdev, qv[i]))

@@ -302,7 +309,7 @@ static void rtw8822c_dac_cal_iq_sample(struct rtw_dev *rtwdev, u32 *iv, u32 *qv)
 }
 
 static void rtw8822c_dac_cal_iq_search(struct rtw_dev *rtwdev,
-				       u32 *iv, u32 *qv,
+				       s32 *iv, s32 *qv,
 				       u32 *i_value, u32 *q_value)
 {
 	u32 i_max = 0, q_max = 0, i_min = 0, q_min = 0;

@@ -311,13 +318,13 @@ static void rtw8822c_dac_cal_iq_search(struct rtw_dev *rtwdev,
 	int i, cnt = 0;
 
 	do {
-		i_min = iv[0];
-		i_max = iv[0];
-		q_min = qv[0];
-		q_max = qv[0];
+		i_min = (u32)iv[0];
+		i_max = (u32)iv[0];
+		q_min = (u32)qv[0];
+		q_max = (u32)qv[0];
 		for (i = 0; i < DACK_SN_8822C; i++) {
-			rtw8822c_rf_minmax_cmp(rtwdev, iv[i], &i_min, &i_max);
-			rtw8822c_rf_minmax_cmp(rtwdev, qv[i], &q_min, &q_max);
+			rtw8822c_rf_minmax_cmp(rtwdev, iv[i], (s32 *)&i_min, (s32 *)&i_max);
+			rtw8822c_rf_minmax_cmp(rtwdev, qv[i], (s32 *)&q_min, (s32 *)&q_max);
 		}
 
 		if (i_max < 0x200 && i_min < 0x200)

@@ -345,11 +352,11 @@ static void rtw8822c_dac_cal_iq_search(struct rtw_dev *rtwdev,
 
 		if (i_delta > 5 || q_delta > 5) {
 			temp = rtw_read32_mask(rtwdev, 0x2dbc, 0x3fffff);
-			iv[0] = (temp & 0x3ff000) >> 12;
-			qv[0] = temp & 0x3ff;
+			iv[0] = (s32)((temp & 0x3ff000) >> 12);
+			qv[0] = (s32)(temp & 0x3ff);
 			temp = rtw_read32_mask(rtwdev, 0x2dbc, 0x3fffff);
-			iv[DACK_SN_8822C - 1] = (temp & 0x3ff000) >> 12;
-			qv[DACK_SN_8822C - 1] = temp & 0x3ff;
+			iv[DACK_SN_8822C - 1] = (s32)((temp & 0x3ff000) >> 12);
+			qv[DACK_SN_8822C - 1] = (s32)(temp & 0x3ff);
 		} else {
 			break;
 		}

@@ -362,7 +369,7 @@ static void rtw8822c_dac_cal_iq_search(struct rtw_dev *rtwdev,
 static void rtw8822c_dac_cal_rf_mode(struct rtw_dev *rtwdev,
 				     u32 *i_value, u32 *q_value)
 {
-	u32 iv[DACK_SN_8822C], qv[DACK_SN_8822C];
+	s32 iv[DACK_SN_8822C], qv[DACK_SN_8822C];
 	u32 rf_a, rf_b;
 
 	rf_a = rtw_read_rf(rtwdev, RF_PATH_A, 0x0, RFREG_MASK);

Signature · 1 line

2.55.0

Arsenii Pashchenko

author

2026-08-13 05:48 UTC #2 lore raw

PATCH v2 2/4 wifi: rtw88: rtw8822c: use sign_extend32 for DAC IQ validation

In reply to Arsenii Pashchenko

Leverage the kernel's native sign_extend32() macro to properly interpret the 10-bit raw values from hardware registers as signed 32-bit (s10) integers covering the [-512, 511] range.

This allows us to completely rewrite rtw8822c_dac_iq_check() to use a simple, clean amplitude boundary check instead of complex, nested unsigned boundary conditions. Drop the temporary u32 casts inside the check and sampling routines.

Signed-off-by Arsenii Pashchenko <[email protected]>

---
 drivers/net/wireless/realtek/rtw88/rtw8822c.c | 24 +++++++++----------
 1 file changed, 11 insertions(+), 13 deletions(-)

drivers/net/wireless/realtek/rtw88/rtw8822c.c +11 ~~-13~~

index 896e3e7b9..d06986d09 100644
@@ -3,6 +3,7 @@
  */
 
 #include <linux/module.h>
+#include <linux/bitops.h>
 #include "main.h"
 #include "coex.h"
 #include "fw.h"

@@ -277,18 +278,15 @@ static u32 rtw8822c_get_path_read_addr(u8 path)
 	return base_addr;
 }
 
-static bool rtw8822c_dac_iq_check(struct rtw_dev *rtwdev, s32 value_s32)
+static bool rtw8822c_dac_iq_check(struct rtw_dev *rtwdev, s32 value)
 {
-	u32 value = (u32)value_s32;
-	bool ret = true;
 
-	if ((value >= 0x200 && (0x400 - value) > 0x64) ||
-	    (value < 0x200 && value > 0x64)) {
-		ret = false;
+	if (value > 100 || value < -100) {
 		rtw_dbg(rtwdev, RTW_DBG_RFK, "[DACK] Error overflow\n");
+		return false;
 	}
 
-	return ret;
+	return true;
 }
 
 static void rtw8822c_dac_cal_iq_sample(struct rtw_dev *rtwdev, s32 *iv, s32 *qv)

@@ -299,8 +297,8 @@ static void rtw8822c_dac_cal_iq_sample(struct rtw_dev *rtwdev, s32 *iv, s32 *qv)
 	while (i < DACK_SN_8822C && cnt < 10000) {
 		cnt++;
 		temp = rtw_read32_mask(rtwdev, 0x2dbc, 0x3fffff);
-		iv[i] = (s32)((temp & 0x3ff000) >> 12);
-		qv[i] = (s32)(temp & 0x3ff);
+		iv[i] = sign_extend32((temp & 0x3ff000) >> 12, 9);
+		qv[i] = sign_extend32(temp & 0x3ff, 9);
 
 		if (rtw8822c_dac_iq_check(rtwdev, iv[i]) &&
 		    rtw8822c_dac_iq_check(rtwdev, qv[i]))

@@ -352,11 +350,11 @@ static void rtw8822c_dac_cal_iq_search(struct rtw_dev *rtwdev,
 
 		if (i_delta > 5 || q_delta > 5) {
 			temp = rtw_read32_mask(rtwdev, 0x2dbc, 0x3fffff);
-			iv[0] = (s32)((temp & 0x3ff000) >> 12);
-			qv[0] = (s32)(temp & 0x3ff);
+			iv[0] = sign_extend32((temp & 0x3ff000) >> 12, 9);
+			qv[0] = sign_extend32(temp & 0x3ff, 9);
 			temp = rtw_read32_mask(rtwdev, 0x2dbc, 0x3fffff);
-			iv[DACK_SN_8822C - 1] = (s32)((temp & 0x3ff000) >> 12);
-			qv[DACK_SN_8822C - 1] = (s32)(temp & 0x3ff);
+			iv[DACK_SN_8822C - 1] = sign_extend32((temp & 0x3ff000) >> 12, 9);
+			qv[DACK_SN_8822C - 1] = sign_extend32(temp & 0x3ff, 9);
 		} else {
 			break;
 		}

Signature · 1 line

2.55.0

Arsenii Pashchenko

author

2026-08-13 05:48 UTC #3 lore raw

PATCH v2 3/4 wifi: rtw88: rtw8822c: switch to the kernel's sort() library

In reply to Arsenii Pashchenko

Replace the custom, nested bubble-sort logic in rtw8822c_dac_iq_sort() and __rtw8822c_dac_iq_sort() with a call to the kernel's optimized heapsort implementation.

Implement a concise, localized s32 comparator. Since the previous patch already guarantees that input values are properly sign-extended into signed arrays, the custom circular index sorting rules completely disappear, trimming down lines of code.

Signed-off-by Arsenii Pashchenko <[email protected]>

---
 drivers/net/wireless/realtek/rtw88/rtw8822c.c | 28 ++++++-------------
 1 file changed, 8 insertions(+), 20 deletions(-)

drivers/net/wireless/realtek/rtw88/rtw8822c.c +8 ~~-20~~

index d06986d09..642ac2e2b 100644
@@ -4,6 +4,7 @@
 
 #include <linux/module.h>
 #include <linux/bitops.h>
+#include <linux/sort.h>
 #include "main.h"
 #include "coex.h"
 #include "fw.h"

@@ -186,31 +187,18 @@ static void rtw8822c_rf_minmax_cmp(struct rtw_dev *rtwdev, s32 value_s32,
 	}
 }
 
-static void __rtw8822c_dac_iq_sort(struct rtw_dev *rtwdev, s32 *v1_s32, s32 *v2_s32)
+static int rtw8822c_dac_iq_cmp_s32(const void *a, const void *b)
 {
-	u32 *v1 = (u32 *)v1_s32;
-	u32 *v2 = (u32 *)v2_s32;
-	if (*v1 >= 0x200 && *v2 >= 0x200) {
-		if (*v1 > *v2)
-			swap(*v1, *v2);
-	} else if (*v1 < 0x200 && *v2 < 0x200) {
-		if (*v1 > *v2)
-			swap(*v1, *v2);
-	} else if (*v1 < 0x200 && *v2 >= 0x200) {
-		swap(*v1, *v2);
-	}
+	s32 va = *(const s32 *)a;
+	s32 vb = *(const s32 *)b;
+
+	return (va > vb) - (va < vb);
 }
 
 static void rtw8822c_dac_iq_sort(struct rtw_dev *rtwdev, s32 *iv, s32 *qv)
 {
-	u32 i, j;
-
-	for (i = 0; i < DACK_SN_8822C - 1; i++) {
-		for (j = 0; j < (DACK_SN_8822C - 1 - i) ; j++) {
-			__rtw8822c_dac_iq_sort(rtwdev, &iv[j], &iv[j + 1]);
-			__rtw8822c_dac_iq_sort(rtwdev, &qv[j], &qv[j + 1]);
-		}
-	}
+	sort(iv, DACK_SN_8822C, sizeof(s32), rtw8822c_dac_iq_cmp_s32, NULL);
+	sort(qv, DACK_SN_8822C, sizeof(s32), rtw8822c_dac_iq_cmp_s32, NULL);
 }
 
 static void rtw8822c_dac_iq_offset(struct rtw_dev *rtwdev, s32 *vec_s32, u32 *val)

Signature · 1 line

2.55.0

Arsenii Pashchenko

author

2026-08-13 05:48 UTC #4 lore raw

PATCH v2 4/4 wifi: rtw88: rtw8822c: simplify amplitude search and offset via s32

In reply to Arsenii Pashchenko

Complete the signed data transition by removing the complex rtw8822c_rf_minmax_cmp() helper. On a true linear s32 scale, finding the delta amplitude simplifies to a direct difference (max - min) without any nested circular wrap-around conditions.

Refactor rtw8822c_dac_iq_offset() to directly calculate the trimmed arithmetic mean, casting back to the hardware register's offset orientation only at the final assignment using a ternary operator.

Signed-off-by Arsenii Pashchenko <[email protected]>

---
 drivers/net/wireless/realtek/rtw88/rtw8822c.c | 103 +++++-------------
 1 file changed, 25 insertions(+), 78 deletions(-)

drivers/net/wireless/realtek/rtw88/rtw8822c.c +25 ~~-78~~

index 642ac2e2b..6fcdfc64c 100644
@@ -155,38 +155,6 @@ static void rtw8822c_dac_restore_reg(struct rtw_dev *rtwdev,
 	}
 }
 
-static void rtw8822c_rf_minmax_cmp(struct rtw_dev *rtwdev, s32 value_s32,
-				   s32 *min_s32, s32 *max_s32)
-{
-	u32 value = (u32)value_s32;
-	u32 *min = (u32 *)min_s32;
-	u32 *max = (u32 *)max_s32;
-	if (value >= 0x200) {
-		if (*min >= 0x200) {
-			if (*min > value)
-				*min = value;
-		} else {
-			*min = value;
-		}
-		if (*max >= 0x200) {
-			if (*max < value)
-				*max = value;
-		}
-	} else {
-		if (*min < 0x200) {
-			if (*min > value)
-				*min = value;
-		}
-
-		if (*max  >= 0x200) {
-			*max = value;
-		} else {
-			if (*max < value)
-				*max = value;
-		}
-	}
-}
-
 static int rtw8822c_dac_iq_cmp_s32(const void *a, const void *b)
 {
 	s32 va = *(const s32 *)a;

@@ -201,31 +169,16 @@ static void rtw8822c_dac_iq_sort(struct rtw_dev *rtwdev, s32 *iv, s32 *qv)
 	sort(qv, DACK_SN_8822C, sizeof(s32), rtw8822c_dac_iq_cmp_s32, NULL);
 }
 
-static void rtw8822c_dac_iq_offset(struct rtw_dev *rtwdev, s32 *vec_s32, u32 *val)
+static s32 rtw8822c_dac_iq_offset(struct rtw_dev *rtwdev, s32 *vec)
 {
-	u32 *vec = (u32 *)vec_s32;
-	u32 p, m, t, i;
+	s32 sum = 0;
 
-	m = 0;
-	p = 0;
-	for (i = 10; i < DACK_SN_8822C - 10; i++) {
-		if (vec[i] > 0x200)
-			m = (0x400 - vec[i]) + m;
-		else
-			p = vec[i] + p;
-	}
+	for (u32 i = 10; i < DACK_SN_8822C - 10; i++)
+		sum += vec[i];
 
-	if (p > m) {
-		t = p - m;
-		t = t / (DACK_SN_8822C - 20);
-	} else {
-		t = m - p;
-		t = t / (DACK_SN_8822C - 20);
-		if (t != 0x0)
-			t = 0x400 - t;
-	}
+	s32 avg = sum / (DACK_SN_8822C - 20);
 
-	*val = t;
+	return avg >= 0 ? avg : 0x400 + avg;
 }
 
 static u32 rtw8822c_get_path_write_addr(u8 path)

@@ -280,7 +233,7 @@ static bool rtw8822c_dac_iq_check(struct rtw_dev *rtwdev, s32 value)
 static void rtw8822c_dac_cal_iq_sample(struct rtw_dev *rtwdev, s32 *iv, s32 *qv)
 {
 	u32 temp;
-	int i = 0, cnt = 0;
+	u32 i = 0, cnt = 0;
 
 	while (i < DACK_SN_8822C && cnt < 10000) {
 		cnt++;

@@ -298,34 +251,28 @@ static void rtw8822c_dac_cal_iq_search(struct rtw_dev *rtwdev,
 				       s32 *iv, s32 *qv,
 				       u32 *i_value, u32 *q_value)
 {
-	u32 i_max = 0, q_max = 0, i_min = 0, q_min = 0;
-	u32 i_delta, q_delta;
+	s32 i_max = 0, q_max = 0, i_min = 0, q_min = 0;
 	u32 temp;
-	int i, cnt = 0;
+	u32 i, cnt = 0;
 
 	do {
-		i_min = (u32)iv[0];
-		i_max = (u32)iv[0];
-		q_min = (u32)qv[0];
-		q_max = (u32)qv[0];
+		i_min = iv[0];
+		i_max = iv[0];
+		q_min = qv[0];
+		q_max = qv[0];
 		for (i = 0; i < DACK_SN_8822C; i++) {
-			rtw8822c_rf_minmax_cmp(rtwdev, iv[i], (s32 *)&i_min, (s32 *)&i_max);
-			rtw8822c_rf_minmax_cmp(rtwdev, qv[i], (s32 *)&q_min, (s32 *)&q_max);
+			if (iv[i] < i_min)
+				i_min = iv[i];
+			if (iv[i] > i_max)
+				i_max = iv[i];
+			if (qv[i] < q_min)
+				q_min = qv[i];
+			if (qv[i] > q_max)
+				q_max = qv[i];
 		}
 
-		if (i_max < 0x200 && i_min < 0x200)
-			i_delta = i_max - i_min;
-		else if (i_max >= 0x200 && i_min >= 0x200)
-			i_delta = i_max - i_min;
-		else
-			i_delta = i_max + (0x400 - i_min);
-
-		if (q_max < 0x200 && q_min < 0x200)
-			q_delta = q_max - q_min;
-		else if (q_max >= 0x200 && q_min >= 0x200)
-			q_delta = q_max - q_min;
-		else
-			q_delta = q_max + (0x400 - q_min);
+		u32 i_delta = (u32)(i_max - i_min);
+		u32 q_delta = (u32)(q_max - q_min);
 
 		rtw_dbg(rtwdev, RTW_DBG_RFK,
 			"[DACK] i: min=0x%08x, max=0x%08x, delta=0x%08x\n",

@@ -348,8 +295,8 @@ static void rtw8822c_dac_cal_iq_search(struct rtw_dev *rtwdev,
 		}
 	} while (cnt++ < 100);
 
-	rtw8822c_dac_iq_offset(rtwdev, iv, i_value);
-	rtw8822c_dac_iq_offset(rtwdev, qv, q_value);
+	*i_value = rtw8822c_dac_iq_offset(rtwdev, iv);
+	*q_value = rtw8822c_dac_iq_offset(rtwdev, qv);
 }
 
 static void rtw8822c_dac_cal_rf_mode(struct rtw_dev *rtwdev,

Signature · 1 line

2.55.0

Ping-Ke Shih

maintainer

2026-08-13 05:54 UTC #5 lore raw

In reply to Arsenii Pashchenko

Quoted 1 line

- Fixed missing target tree name in the subject prefix (switched to wireless-next).

The correct tree tag is rtw-next. https://github.com/pkshih/rtw.git