[PATCH 08/18] wifi: mt76: mt7925: guard mac_reset against MT7927 DMA destruction

[Javier Tia]

On MT7927 hardware, the mac_reset path performs CLR_OWN and WPDMA logic
reset, both of which destroy DMA ring configuration. CLR_OWN triggers
the ROM to reinitialize WFDMA, and the logic reset pulse disrupts the
WFDMA state that mt7927_dma_init() carefully configured.

A full MT7927 reset requires re-running the DMA initialization sequence,
which is not yet implemented in the recovery path. Return -EOPNOTSUPP
with a warning so users know to reload the module.

Tested-by: Marcin FM <marcin at lgic.pl>
Tested-by: Cristian-Florin Radoi <radoi.chris at gmail.com>
Tested-by: George Salukvadze <giosal90 at gmail.com>
Tested-by: Evgeny Kapusta <3193631 at gmail.com>
Tested-by: Samu Toljamo <samu.toljamo at gmail.com>
Tested-by: Ariel Rosenfeld <ariel.rosenfeld.750 at gmail.com>
Tested-by: Chapuis Dario <chapuisdario4 at gmail.com>
Tested-by: Thibaut François <tibo at humeurlibre.fr>
Tested-by: 张旭涵 <Loong.0x00 at gmail.com>
Signed-off-by: Javier Tia <floss at jetm.me>
---
 drivers/net/wireless/mediatek/mt76/mt7925/pci_mac.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7925/pci_mac.c b/drivers/net/wireless/mediatek/mt76/mt7925/pci_mac.c
index 1626a3684082..cf578a2cdc68 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7925/pci_mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7925/pci_mac.c
@@ -72,6 +72,14 @@ int mt7925e_mac_reset(struct mt792x_dev *dev)
 	const struct mt792x_irq_map *irq_map = dev->irq_map;
 	int i, err;
 
+	/* MT7927: CLR_OWN and WPDMA reset destroy DMA ring configuration.
+	 * A full reset requires re-running mt7927_dma_init() which is not
+	 * yet implemented in the recovery path. */
+	if (is_mt7927(&dev->mt76)) {
+		dev_warn(dev->mt76.dev, "MT7927 mac_reset not supported, reload module to recover\n");
+		return -EOPNOTSUPP;
+	}
+
 	mt792xe_mcu_drv_pmctrl(dev);
 
 	mt76_connac_free_pending_tx_skbs(&dev->pm, NULL);

-- 
2.53.0