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Message-ID: <db2bde41-7b89-7e89-ae28-e92b1fe0525b@nbd.name>
Date:   Sat, 12 Nov 2022 19:17:37 +0100
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Subject: Re: [PATCH 2/4] wifi: mt76: mt7915: Fix chainmask calculation on
 mt7915 DBDC
Content-Language: en-US
To:     Nicolas Cavallari <nicolas.cavallari@green-communications.fr>,
        linux-wireless@vger.kernel.org
Cc:     Lorenzo Bianconi <lorenzo@kernel.org>,
        Ryder Lee <ryder.lee@mediatek.com>,
        Shayne Chen <shayne.chen@mediatek.com>,
        Sean Wang <sean.wang@mediatek.com>
References: <20221110153953.22562-1-nicolas.cavallari@green-communications.fr>
 <20221110153953.22562-3-nicolas.cavallari@green-communications.fr>
From:   Felix Fietkau <nbd@nbd.name>
In-Reply-To: <20221110153953.22562-3-nicolas.cavallari@green-communications.fr>
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On 10.11.22 16:39, Nicolas Cavallari wrote:
> mt7915 does not have a per-band number of chains unlike the other chips,
> it only has a total number of chains.  Yet the current code would
> consider the total number as a per-band number.
> 
> For example, it would report that a 2x2 + 2x2 DBDC card have 4 chains on
> each band and set chainmask to 0b1111 for the first interface and
> 0b11110000 for the second.
> 
> Fixes: 99ad32a4ca3a ("mt76: mt7915: add support for MT7986")
> Signed-off-by: Nicolas Cavallari <nicolas.cavallari@green-communications.fr>
> ---
>   drivers/net/wireless/mediatek/mt76/mt7915/eeprom.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/mt7915/eeprom.c b/drivers/net/wireless/mediatek/mt76/mt7915/eeprom.c
> index 83bced0c0785..8bb971018a1e 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt7915/eeprom.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt7915/eeprom.c
> @@ -194,6 +194,7 @@ void mt7915_eeprom_parse_hw_cap(struct mt7915_dev *dev,
>   	nss = path;
>   	if (dev->dbdc_support) {
>   		if (is_mt7915(&dev->mt76)) {
> +			path = path / 2;
>   			nss = FIELD_GET(MT_EE_WIFI_CONF3_TX_PATH_B0,
>   					eeprom[MT_EE_WIFI_CONF + 3]);
>   			if (phy->band_idx)
This was causing a regression on properly calibrated DBDC cards, where
the 'path' variable contains the per-band path, not the total path.
I've folded in the following change to fix your commit:

--- a/drivers/net/wireless/mediatek/mt76/mt7915/eeprom.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7915/eeprom.c
@@ -194,7 +194,7 @@ void mt7915_eeprom_parse_hw_cap(struct mt7915_dev *dev,
  	nss = path;
  	if (dev->dbdc_support) {
  		if (is_mt7915(&dev->mt76)) {
-			path = path / 2;
+			path = min_t(u8, path, 2);
  			nss = FIELD_GET(MT_EE_WIFI_CONF3_TX_PATH_B0,
  					eeprom[MT_EE_WIFI_CONF + 3]);
  			if (phy->band_idx)