[PATCH wireless] wifi: mt76: mt7915: add module param to select 5 GHz or 6 GHz on MT7916

[Felix Fietkau <nbd@nbd.name>]

From: Shayne Chen <shayne.chen@mediatek.com>

Due to a limitation in available memory, the MT7916 firmware can only
handle either 5 GHz or 6 GHz at a time. It does not support runtime
switching without a full restart.

On older firmware, this accidentally worked to some degree due to missing
checks, but couldn't be supported properly, because it left the 6 GHz
channels uncalibrated.
Newer firmware refuses to start on either band if the passed EEPROM
data indicates support for both.

Deal with this limitation by using a module parameter to specify the
preferred band in case both are supported.

Fixes: b4d093e321bd ("mt76: mt7915: add 6 GHz support")
Cc: stable@vger.kernel.org
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 .../wireless/mediatek/mt76/mt7915/eeprom.c    | 21 +++++++++++++++++--
 .../net/wireless/mediatek/mt76/mt7915/init.c  |  4 ++--
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7915/eeprom.c b/drivers/net/wireless/mediatek/mt76/mt7915/eeprom.c
index bfdbc15abaa9..928e0b07a9bf 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7915/eeprom.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7915/eeprom.c
@@ -2,9 +2,14 @@
 /* Copyright (C) 2020 MediaTek Inc. */
 
 #include <linux/firmware.h>
+#include <linux/moduleparam.h>
 #include "mt7915.h"
 #include "eeprom.h"
 
+static bool enable_6ghz;
+module_param(enable_6ghz, bool, 0644);
+MODULE_PARM_DESC(enable_6ghz, "Enable 6 GHz instead of 5 GHz on hardware that supports both");
+
 static int mt7915_eeprom_load_precal(struct mt7915_dev *dev)
 {
 	struct mt76_dev *mdev = &dev->mt76;
@@ -170,8 +175,20 @@ static void mt7915_eeprom_parse_band_config(struct mt7915_phy *phy)
 			phy->mt76->cap.has_6ghz = true;
 			return;
 		case MT_EE_V2_BAND_SEL_5GHZ_6GHZ:
-			phy->mt76->cap.has_5ghz = true;
-			phy->mt76->cap.has_6ghz = true;
+			if (enable_6ghz) {
+				phy->mt76->cap.has_6ghz = true;
+				u8p_replace_bits(&eeprom[MT_EE_WIFI_CONF + band],
+						 MT_EE_V2_BAND_SEL_6GHZ,
+						 MT_EE_WIFI_CONF0_BAND_SEL);
+			} else {
+				phy->mt76->cap.has_5ghz = true;
+				u8p_replace_bits(&eeprom[MT_EE_WIFI_CONF + band],
+						 MT_EE_V2_BAND_SEL_5GHZ,
+						 MT_EE_WIFI_CONF0_BAND_SEL);
+			}
+			/* force to buffer mode */
+			dev->flash_mode = true;
+
 			return;
 		default:
 			phy->mt76->cap.has_2ghz = true;
diff --git a/drivers/net/wireless/mediatek/mt76/mt7915/init.c b/drivers/net/wireless/mediatek/mt76/mt7915/init.c
index 6bef96e3d2a3..f82216d1bda0 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7915/init.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7915/init.c
@@ -1239,14 +1239,14 @@ int mt7915_register_device(struct mt7915_dev *dev)
 	if (ret)
 		goto unreg_dev;
 
-	ieee80211_queue_work(mt76_hw(dev), &dev->init_work);
-
 	if (phy2) {
 		ret = mt7915_register_ext_phy(dev, phy2);
 		if (ret)
 			goto unreg_thermal;
 	}
 
+	ieee80211_queue_work(mt76_hw(dev), &dev->init_work);
+
 	dev->recovery.hw_init_done = true;
 
 	ret = mt7915_init_debugfs(&dev->phy);
-- 
2.46.0