ath9k: use consistent value for REDUCE_SCALED_POWER_BY_THREE_CHAIN

PATCH Superseded Gabor Juhos 3 participants 9 messages Apr 14, 2012 – Apr 15, 2012 Qualcomm Atheros ATH9K wireless driver

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Gabor Juhos

author

2012-04-14 20:01 UTC #0 lore raw

PATCH 1/3 ath9k: use consistent value for REDUCE_SCALED_POWER_BY_THREE_CHAIN

The REDUCE_SCALED_POWER_BY_THREE_CHAIN symbol is defined in different eeprom files, and the value varies between the different files.

In eeprom_def.c and in ar9003_eeprom.c the value of the symbol is 9, however the comments in these files indicates the value should be 10*log10(3)*2 which is 9.54242509439325. Replace the the value to 10 in these files.

Also add comments to eeprom_9287.c.

Signed-off-by Gabor Juhos <[email protected]>

---
 drivers/net/wireless/ath/ath9k/ar9003_eeprom.c |    2 +-
 drivers/net/wireless/ath/ath9k/eeprom_9287.c   |    4 ++--
 drivers/net/wireless/ath/ath9k/eeprom_def.c    |    2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

drivers/net/wireless/ath/ath9k/ar9003_eeprom.c +1 -1

index 672b6c9..25a4a02 100644
@@ -31,7 +31,7 @@
 #define CTL_11G_EXT (CTL_11G | EXT_ADDITIVE)
 #define CTL_11B_EXT (CTL_11B | EXT_ADDITIVE)
 #define REDUCE_SCALED_POWER_BY_TWO_CHAIN     6  /* 10*log10(2)*2 */
-#define REDUCE_SCALED_POWER_BY_THREE_CHAIN   9  /* 10*log10(3)*2 */
+#define REDUCE_SCALED_POWER_BY_THREE_CHAIN   10 /* 10*log10(3)*2 */
 #define PWRINCR_3_TO_1_CHAIN      9             /* 10*log(3)*2 */
 #define PWRINCR_3_TO_2_CHAIN      3             /* floor(10*log(3/2)*2) */
 #define PWRINCR_2_TO_1_CHAIN      6             /* 10*log(2)*2 */

drivers/net/wireless/ath/ath9k/eeprom_9287.c +2 -2

index f272236..604eab8 100644
@@ -564,8 +564,8 @@ static void ath9k_hw_set_ar9287_power_per_rate_table(struct ath_hw *ah,
 	(((cfgCtl & ~CTL_MODE_M) | (pCtlMode[ctlMode] & CTL_MODE_M)) == \
 	 ((pEepData->ctlIndex[i] & CTL_MODE_M) | SD_NO_CTL))
 
-#define REDUCE_SCALED_POWER_BY_TWO_CHAIN     6
-#define REDUCE_SCALED_POWER_BY_THREE_CHAIN   10
+#define REDUCE_SCALED_POWER_BY_TWO_CHAIN     6  /* 10*log10(2)*2 */
+#define REDUCE_SCALED_POWER_BY_THREE_CHAIN   10 /* 10*log10(3)*2 */
 
 	u16 twiceMaxEdgePower;
 	int i;

drivers/net/wireless/ath/ath9k/eeprom_def.c +1 -1

index 619b95d..0068627 100644
@@ -992,7 +992,7 @@ static void ath9k_hw_set_def_power_per_rate_table(struct ath_hw *ah,
 						  u16 powerLimit)
 {
 #define REDUCE_SCALED_POWER_BY_TWO_CHAIN     6  /* 10*log10(2)*2 */
-#define REDUCE_SCALED_POWER_BY_THREE_CHAIN   9 /* 10*log10(3)*2 */
+#define REDUCE_SCALED_POWER_BY_THREE_CHAIN   10 /* 10*log10(3)*2 */
 
 	struct ar5416_eeprom_def *pEepData = &ah->eeprom.def;
 	u16 twiceMaxEdgePower;

Signature · 1 line

1.7.2.1

Gabor Juhos

author

2012-04-14 20:01 UTC #1 lore raw

PATCH 2/3 ath9k: introduce ath9k_hw_get_scaled_power helper

The computation of the scaled power value in various eeprom files uses identical code. Move that code into a helper function and use that instead of code duplication.

Signed-off-by Gabor Juhos <[email protected]>

---
 drivers/net/wireless/ath/ath9k/ar9003_eeprom.c |   28 +------------------
 drivers/net/wireless/ath/ath9k/eeprom.c        |   33 ++++++++++++++++++++++++
 drivers/net/wireless/ath/ath9k/eeprom.h        |    5 +++
 drivers/net/wireless/ath/ath9k/eeprom_9287.c   |   30 +--------------------
 drivers/net/wireless/ath/ath9k/eeprom_def.c    |   23 +---------------
 5 files changed, 44 insertions(+), 75 deletions(-)

drivers/net/wireless/ath/ath9k/ar9003_eeprom.c +2 ~~-26~~

index 25a4a02..d254571 100644
@@ -30,8 +30,6 @@
 #define CTL_11A_EXT (CTL_11A | EXT_ADDITIVE)
 #define CTL_11G_EXT (CTL_11G | EXT_ADDITIVE)
 #define CTL_11B_EXT (CTL_11B | EXT_ADDITIVE)
-#define REDUCE_SCALED_POWER_BY_TWO_CHAIN     6  /* 10*log10(2)*2 */
-#define REDUCE_SCALED_POWER_BY_THREE_CHAIN   10 /* 10*log10(3)*2 */
 #define PWRINCR_3_TO_1_CHAIN      9             /* 10*log(3)*2 */
 #define PWRINCR_3_TO_2_CHAIN      3             /* floor(10*log(3/2)*2) */
 #define PWRINCR_2_TO_1_CHAIN      6             /* 10*log(2)*2 */

@@ -4789,30 +4787,8 @@ static void ar9003_hw_set_power_per_rate_table(struct ath_hw *ah,
 	bool is2ghz = IS_CHAN_2GHZ(chan);
 
 	ath9k_hw_get_channel_centers(ah, chan, &centers);
-	scaledPower = powerLimit - antenna_reduction;
-
-	/*
-	 * Reduce scaled Power by number of chains active to get
-	 * to per chain tx power level
-	 */
-	switch (ar5416_get_ntxchains(ah->txchainmask)) {
-	case 1:
-		break;
-	case 2:
-		if (scaledPower > REDUCE_SCALED_POWER_BY_TWO_CHAIN)
-			scaledPower -= REDUCE_SCALED_POWER_BY_TWO_CHAIN;
-		else
-			scaledPower = 0;
-		break;
-	case 3:
-		if (scaledPower > REDUCE_SCALED_POWER_BY_THREE_CHAIN)
-			scaledPower -= REDUCE_SCALED_POWER_BY_THREE_CHAIN;
-		else
-			scaledPower = 0;
-		break;
-	}
-
-	scaledPower = max((u16)0, scaledPower);
+	scaledPower = ath9k_hw_get_scaled_power(ah, powerLimit,
+						antenna_reduction);
 
 	/*
 	 * Get target powers from EEPROM - our baseline for TX Power

drivers/net/wireless/ath/ath9k/eeprom.c +33 -0

index c435232..61bad99 100644
@@ -290,6 +290,39 @@ u16 ath9k_hw_get_max_edge_power(u16 freq, struct cal_ctl_edges *pRdEdgesPower,
 	return twiceMaxEdgePower;
 }
 
+u16 ath9k_hw_get_scaled_power(struct ath_hw *ah, u16 power_limit,
+			      u8 antenna_reduction)
+{
+	u16 scaled_power;
+
+	scaled_power = power_limit - antenna_reduction;
+
+	/*
+	 * Reduce scaled Power by number of chains active
+	 * to get the per chain tx power level.
+	 */
+	switch (ar5416_get_ntxchains(ah->txchainmask)) {
+	case 1:
+		break;
+	case 2:
+		if (scaled_power > REDUCE_SCALED_POWER_BY_TWO_CHAIN)
+			scaled_power -= REDUCE_SCALED_POWER_BY_TWO_CHAIN;
+		else
+			scaled_power = 0;
+		break;
+	case 3:
+		if (scaled_power > REDUCE_SCALED_POWER_BY_THREE_CHAIN)
+			scaled_power -= REDUCE_SCALED_POWER_BY_THREE_CHAIN;
+		else
+			scaled_power = 0;
+		break;
+	}
+
+	scaled_power = max((u16)0, scaled_power);
+
+	return scaled_power;
+}
+
 void ath9k_hw_update_regulatory_maxpower(struct ath_hw *ah)
 {
 	struct ath_common *common = ath9k_hw_common(ah);

drivers/net/wireless/ath/ath9k/eeprom.h +5 -0

index 5ff7ab9..8d779b4 100644
@@ -82,6 +82,9 @@
 #define INCREASE_MAXPOW_BY_TWO_CHAIN     6  /* 10*log10(2)*2 */
 #define INCREASE_MAXPOW_BY_THREE_CHAIN   10 /* 10*log10(3)*2 */
 
+#define REDUCE_SCALED_POWER_BY_TWO_CHAIN	6  /* 10*log10(2)*2 */
+#define REDUCE_SCALED_POWER_BY_THREE_CHAIN	10 /* 10*log10(3)*2 */
+
 /*
  * For AR9285 and later chipsets, the following bits are not being programmed
  * in EEPROM and so need to be enabled always.

@@ -686,6 +689,8 @@ void ath9k_hw_get_target_powers(struct ath_hw *ah,
 				u16 numRates, bool isHt40Target);
 u16 ath9k_hw_get_max_edge_power(u16 freq, struct cal_ctl_edges *pRdEdgesPower,
 				bool is2GHz, int num_band_edges);
+u16 ath9k_hw_get_scaled_power(struct ath_hw *ah, u16 power_limit,
+			      u8 antenna_reduction);
 void ath9k_hw_update_regulatory_maxpower(struct ath_hw *ah);
 int ath9k_hw_eeprom_init(struct ath_hw *ah);

drivers/net/wireless/ath/ath9k/eeprom_9287.c +2 ~~-28~~

index 604eab8..5ab0e6e 100644
@@ -564,9 +564,6 @@ static void ath9k_hw_set_ar9287_power_per_rate_table(struct ath_hw *ah,
 	(((cfgCtl & ~CTL_MODE_M) | (pCtlMode[ctlMode] & CTL_MODE_M)) == \
 	 ((pEepData->ctlIndex[i] & CTL_MODE_M) | SD_NO_CTL))
 
-#define REDUCE_SCALED_POWER_BY_TWO_CHAIN     6  /* 10*log10(2)*2 */
-#define REDUCE_SCALED_POWER_BY_THREE_CHAIN   10 /* 10*log10(3)*2 */
-
 	u16 twiceMaxEdgePower;
 	int i;
 	struct cal_ctl_data_ar9287 *rep;

@@ -591,29 +588,8 @@ static void ath9k_hw_set_ar9287_power_per_rate_table(struct ath_hw *ah,
 	tx_chainmask = ah->txchainmask;
 
 	ath9k_hw_get_channel_centers(ah, chan, &centers);
-	scaledPower = powerLimit - antenna_reduction;
-
-	/*
-	 * Reduce scaled Power by number of chains active
-	 * to get the per chain tx power level.
-	 */
-	switch (ar5416_get_ntxchains(tx_chainmask)) {
-	case 1:
-		break;
-	case 2:
-		if (scaledPower > REDUCE_SCALED_POWER_BY_TWO_CHAIN)
-			scaledPower -= REDUCE_SCALED_POWER_BY_TWO_CHAIN;
-		else
-			scaledPower = 0;
-		break;
-	case 3:
-		if (scaledPower > REDUCE_SCALED_POWER_BY_THREE_CHAIN)
-			scaledPower -= REDUCE_SCALED_POWER_BY_THREE_CHAIN;
-		else
-			scaledPower = 0;
-		break;
-	}
-	scaledPower = max((u16)0, scaledPower);
+	scaledPower = ath9k_hw_get_scaled_power(ah, powerLimit,
+						antenna_reduction);
 
 	/*
 	 * Get TX power from EEPROM.

@@ -786,8 +762,6 @@ static void ath9k_hw_set_ar9287_power_per_rate_table(struct ath_hw *ah,
 
 #undef CMP_CTL
 #undef CMP_NO_CTL
-#undef REDUCE_SCALED_POWER_BY_TWO_CHAIN
-#undef REDUCE_SCALED_POWER_BY_THREE_CHAIN
 }
 
 static void ath9k_hw_ar9287_set_txpower(struct ath_hw *ah,

drivers/net/wireless/ath/ath9k/eeprom_def.c +2 ~~-21~~

index 0068627..3a9c9ed 100644
@@ -991,9 +991,6 @@ static void ath9k_hw_set_def_power_per_rate_table(struct ath_hw *ah,
 						  u16 antenna_reduction,
 						  u16 powerLimit)
 {
-#define REDUCE_SCALED_POWER_BY_TWO_CHAIN     6  /* 10*log10(2)*2 */
-#define REDUCE_SCALED_POWER_BY_THREE_CHAIN   10 /* 10*log10(3)*2 */
-
 	struct ar5416_eeprom_def *pEepData = &ah->eeprom.def;
 	u16 twiceMaxEdgePower;
 	int i;

@@ -1027,24 +1024,8 @@ static void ath9k_hw_set_def_power_per_rate_table(struct ath_hw *ah,
 
 	ath9k_hw_get_channel_centers(ah, chan, &centers);
 
-	scaledPower = powerLimit - antenna_reduction;
-
-	switch (ar5416_get_ntxchains(tx_chainmask)) {
-	case 1:
-		break;
-	case 2:
-		if (scaledPower > REDUCE_SCALED_POWER_BY_TWO_CHAIN)
-			scaledPower -= REDUCE_SCALED_POWER_BY_TWO_CHAIN;
-		else
-			scaledPower = 0;
-		break;
-	case 3:
-		if (scaledPower > REDUCE_SCALED_POWER_BY_THREE_CHAIN)
-			scaledPower -= REDUCE_SCALED_POWER_BY_THREE_CHAIN;
-		else
-			scaledPower = 0;
-		break;
-	}
+	scaledPower = ath9k_hw_get_scaled_power(ah, powerLimit,
+						antenna_reduction);
 
 	if (IS_CHAN_2GHZ(chan)) {
 		numCtlModes = ARRAY_SIZE(ctlModesFor11g) -

Signature · 1 line

1.7.2.1

Gabor Juhos

author

2012-04-14 20:01 UTC #2 lore raw

PATCH 3/3 ath9k: simplify ath9k_hw_get_scaled_power function

In reply to Gabor Juhos

Signed-off-by Gabor Juhos <[email protected]>

---
 drivers/net/wireless/ath/ath9k/eeprom.c |   21 ++++++++-------------
 1 files changed, 8 insertions(+), 13 deletions(-)

drivers/net/wireless/ath/ath9k/eeprom.c +8 ~~-13~~

index 61bad99..6a64dec 100644
@@ -293,9 +293,7 @@ u16 ath9k_hw_get_max_edge_power(u16 freq, struct cal_ctl_edges *pRdEdgesPower,
 u16 ath9k_hw_get_scaled_power(struct ath_hw *ah, u16 power_limit,
 			      u8 antenna_reduction)
 {
-	u16 scaled_power;
-
-	scaled_power = power_limit - antenna_reduction;
+	u16 reduction = antenna_reduction;
 
 	/*
 	 * Reduce scaled Power by number of chains active

@@ -305,22 +303,19 @@ u16 ath9k_hw_get_scaled_power(struct ath_hw *ah, u16 power_limit,
 	case 1:
 		break;
 	case 2:
-		if (scaled_power > REDUCE_SCALED_POWER_BY_TWO_CHAIN)
-			scaled_power -= REDUCE_SCALED_POWER_BY_TWO_CHAIN;
-		else
-			scaled_power = 0;
+		reduction += REDUCE_SCALED_POWER_BY_TWO_CHAIN;
 		break;
 	case 3:
-		if (scaled_power > REDUCE_SCALED_POWER_BY_THREE_CHAIN)
-			scaled_power -= REDUCE_SCALED_POWER_BY_THREE_CHAIN;
-		else
-			scaled_power = 0;
+		reduction += REDUCE_SCALED_POWER_BY_THREE_CHAIN;
 		break;
 	}
 
-	scaled_power = max((u16)0, scaled_power);
+	if (power_limit > reduction)
+		power_limit -= reduction;
+	else
+		power_limit = 0;
 
-	return scaled_power;
+	return power_limit;
 }
 
 void ath9k_hw_update_regulatory_maxpower(struct ath_hw *ah)

Signature · 1 line

1.7.2.1

Daniel Halperin

2012-04-14 22:11 UTC #3 lore raw

PATCH 1/3 ath9k: use consistent value for REDUCE_SCALED_POWER_BY_THREE_CHAIN

In reply to Gabor Juhos

(Failed to reply-all originally, sorry:)

Erm...

Quoted 6 lines · On Sat, Apr 14, 2012 at 1:01 PM, Gabor Juhos?<[email protected]>?wrote:

In eeprom_def.c and in ar9003_eeprom.c the value of the symbol is 9, however the comments in these files indicates the value should be 10*log10(3)*2 which is 9.54242509439325. Replace the the value to 10 in these files.

So the truncated constant is off by a quarter-dB for 9 or for 10. Do the chips care one way or the other? (For comparison, Intel uses 4.5 dB, i.e. 9 in this notation, to mean "divide-by-3". That's what ath9k has now).

Are you making it consistent with some other file that's not mentioned here? If not, why?

Quoted 4 lines

?#define REDUCE_SCALED_POWER_BY_TWO_CHAIN ? ? 6 ?/* 10*log10(2)*2 */
(quoted diff) +1 -1
-#define REDUCE_SCALED_POWER_BY_THREE_CHAIN ? 9 ?/* 10*log10(3)*2 */
+#define REDUCE_SCALED_POWER_BY_THREE_CHAIN ? 10 /* 10*log10(3)*2 */
?#define PWRINCR_3_TO_1_CHAIN ? ? ?9 ? ? ? ? ? ? /* 10*log(3)*2 */

Why only change one of two 9s to a 10? Why not also PWRINCR_3_TO_1_CHAIN?

Dan

Gabor Juhos

author

2012-04-15 17:21 UTC #4 lore raw

PATCH 1/3 ath9k: use consistent value for REDUCE_SCALED_POWER_BY_THREE_CHAIN

Hi Dan,

Thank you for the comments.

Quoted 12 lines

(Failed to reply-all originally, sorry:)
Erm...
Quoted 6 lines · Gabor Juhos
In eeprom_def.c and in ar9003_eeprom.c the value of the symbol is 9, however the comments in these files indicates the value should be 10*log10(3)*2 which is 9.54242509439325. Replace the the value to 10 in these files.

Quoted 4 lines

So the truncated constant is off by a quarter-dB for 9 or for 10. Do the chips care one way or the other? (For comparison, Intel uses 4.5 dB, i.e. 9 in this notation, to mean "divide-by-3". That's what ath9k has now).

In my understanding the value is not related to the chip. It is used for per-chain tx power reduction, in order to ensure regulatory compliance. Using 10 instead of 9 means that the overall tx power will be lower.

Quoted 2 lines

Are you making it consistent with some other file that's not mentioned here? If not, why?

I'm tyring to make it consistent between ar9003_eeprom.c, eeprom_def.c and eeprom_9287.c. The first two files uses 9, whereas eeprom_9287 uses 10.

Considering Felix's comment, I will update the patch and will use 9 instead of
10. Although that will replace the value in eeprom_9287.c, but that should not cause problems, because the AR9287 does not supports 3x3.

Quoted 6 lines

drivers/net/wireless/ath/ath9k/ar9003_eeprom.c line 35
Quoted 4 lines
#define REDUCE_SCALED_POWER_BY_TWO_CHAIN 6 /* 10*log10(2)*2 */
drivers/net/wireless/ath/ath9k/ar9003_eeprom.c +1 -1
-#define REDUCE_SCALED_POWER_BY_THREE_CHAIN   9  /* 10*log10(3)*2 */
+#define REDUCE_SCALED_POWER_BY_THREE_CHAIN   10 /* 10*log10(3)*2 */
 #define PWRINCR_3_TO_1_CHAIN      9             /* 10*log(3)*2 */
Why only change one of two 9s to a 10? Why not also PWRINCR_3_TO_1_CHAIN?

The PWRINCR_* symbols are not used anywhere and should be removed.

-Gabor

Felix Fietkau

2012-04-15 10:31 UTC #5 lore raw

PATCH 1/3 ath9k: use consistent value for REDUCE_SCALED_POWER_BY_THREE_CHAIN

In reply to Gabor Juhos

Quoted 10 lines · Gabor Juhos

The REDUCE_SCALED_POWER_BY_THREE_CHAIN symbol is defined in different eeprom files, and the value varies between the different files.
In eeprom_def.c and in ar9003_eeprom.c the value of the symbol is 9, however the comments in these files indicates the value should be 10*log10(3)*2 which is 9.54242509439325. Replace the the value to 10 in these files.

Quoted 3 lines

Also add comments to eeprom_9287.c.
Signed-off-by Gabor Juhos <[email protected]>

I think we should keep the value 9.
If I understand the logic behind the power increase through chain combining properly, this value only describes the worst-case (wrt. regulatory compliance) upper limit of tx power, whereas in practice the measured combined power output will be much lower than that due to signal/phase differences.
Regulatory compliance is already properly tested on all devices with the truncated value 9, so I don't think that we need to be even more conservative and round up here.

- Felix

Gabor Juhos

author

2012-04-15 17:21 UTC #6 lore raw

PATCH 1/3 ath9k: use consistent value for REDUCE_SCALED_POWER_BY_THREE_CHAIN

Hi Felix,

Thank you for the comments.

Quoted 14 lines · Gabor Juhos

Quoted 10 lines
The REDUCE_SCALED_POWER_BY_THREE_CHAIN symbol is defined in different eeprom files, and the value varies between the different files.
In eeprom_def.c and in ar9003_eeprom.c the value of the symbol is 9, however the comments in these files indicates the value should be 10*log10(3)*2 which is 9.54242509439325. Replace the the value to 10 in these files.
Quoted 3 lines
Also add comments to eeprom_9287.c.
Signed-off-by Gabor Juhos <[email protected]>

Quoted 9 lines

I think we should keep the value 9.
If I understand the logic behind the power increase through chain combining properly, this value only describes the worst-case (wrt. regulatory compliance) upper limit of tx power, whereas in practice the measured combined power output will be much lower than that due to signal/phase differences.
Regulatory compliance is already properly tested on all devices with the truncated value 9, so I don't think that we need to be even more conservative and round up here.

Ok, I will rework the patch.

Apart from the inconsistency between the REDUCE_SCALED_POWER_BY_THREE_CHAIN values, there is another thing which confuses me.

In the 'ath9k_hw_set_*_power_cal_table' functions the driver uses the REDUCE_SCALED_POWER_BY_THREE_CHAIN constant to reduce the power values. In the 'ath9k_hw_update_regulatory_maxpower' function it uses the INCREASE_MAXPOW_BY_THREE_CHAIN constant to compensate the reduction. However the two constants are different. I might be wrong, but in my opinion the driver should use the same constant in both functions.

-Gabor

Felix Fietkau

2012-04-15 17:26 UTC #7 lore raw

PATCH 1/3 ath9k: use consistent value for REDUCE_SCALED_POWER_BY_THREE_CHAIN

Quoted 33 lines · Gabor Juhos

Hi Felix,
Thank you for the comments.
Quoted 14 lines · Gabor Juhos
Quoted 10 lines
The REDUCE_SCALED_POWER_BY_THREE_CHAIN symbol is defined in different eeprom files, and the value varies between the different files.
In eeprom_def.c and in ar9003_eeprom.c the value of the symbol is 9, however the comments in these files indicates the value should be 10*log10(3)*2 which is 9.54242509439325. Replace the the value to 10 in these files.
Quoted 3 lines
Also add comments to eeprom_9287.c.
Signed-off-by Gabor Juhos <[email protected]>
Quoted 9 lines
I think we should keep the value 9.
If I understand the logic behind the power increase through chain combining properly, this value only describes the worst-case (wrt. regulatory compliance) upper limit of tx power, whereas in practice the measured combined power output will be much lower than that due to signal/phase differences.
Regulatory compliance is already properly tested on all devices with the truncated value 9, so I don't think that we need to be even more conservative and round up here.
Ok, I will rework the patch.
Apart from the inconsistency between the REDUCE_SCALED_POWER_BY_THREE_CHAIN values, there is another thing which confuses me.

Quoted 6 lines

In the 'ath9k_hw_set_*_power_cal_table' functions the driver uses the REDUCE_SCALED_POWER_BY_THREE_CHAIN constant to reduce the power values. In the 'ath9k_hw_update_regulatory_maxpower' function it uses the INCREASE_MAXPOW_BY_THREE_CHAIN constant to compensate the reduction. However the two constants are different. I might be wrong, but in my opinion the driver should use the same constant in both functions.

I just checked with Atheros sources, and it seems I was wrong about sticking with the value 9.
It appears that Atheros changed it to 10 at some point, and ath9k contains a mix of the old and the new version. Consistently using the value 10 for 3 chains for both increase and reduction seems to be the right thing to do.

- Felix

Gabor Juhos

author

2012-04-15 17:50 UTC #8 lore raw

PATCH 1/3 ath9k: use consistent value for REDUCE_SCALED_POWER_BY_THREE_CHAIN

2012.04.15. 19:26 keltez?ssel, Felix Fietkau ?rta:

Quoted 40 lines · Gabor Juhos

Quoted 33 lines
Hi Felix,
Thank you for the comments.
Quoted 14 lines · Gabor Juhos
Quoted 10 lines
The REDUCE_SCALED_POWER_BY_THREE_CHAIN symbol is defined in different eeprom files, and the value varies between the different files.
In eeprom_def.c and in ar9003_eeprom.c the value of the symbol is 9, however the comments in these files indicates the value should be 10*log10(3)*2 which is 9.54242509439325. Replace the the value to 10 in these files.
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Also add comments to eeprom_9287.c.
Signed-off-by Gabor Juhos <[email protected]>
Quoted 9 lines
I think we should keep the value 9.
If I understand the logic behind the power increase through chain combining properly, this value only describes the worst-case (wrt. regulatory compliance) upper limit of tx power, whereas in practice the measured combined power output will be much lower than that due to signal/phase differences.
Regulatory compliance is already properly tested on all devices with the truncated value 9, so I don't think that we need to be even more conservative and round up here.
Ok, I will rework the patch.
Apart from the inconsistency between the REDUCE_SCALED_POWER_BY_THREE_CHAIN values, there is another thing which confuses me.
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In the 'ath9k_hw_set_*_power_cal_table' functions the driver uses the REDUCE_SCALED_POWER_BY_THREE_CHAIN constant to reduce the power values. In the 'ath9k_hw_update_regulatory_maxpower' function it uses the INCREASE_MAXPOW_BY_THREE_CHAIN constant to compensate the reduction. However the two constants are different. I might be wrong, but in my opinion the driver should use the same constant in both functions.

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I just checked with Atheros sources, and it seems I was wrong about sticking with the value 9.
It appears that Atheros changed it to 10 at some point, and ath9k contains a mix of the old and the new version. Consistently using the value 10 for 3 chains for both increase and reduction seems to be the right thing to do.

Thank you for the information. I will add it to the commit message.

-Gabor