wcn36xx: Put DXE block into reset before freeing memory

When deiniting the DXE hardware we should reset the block to ensure there
is no spurious DMA write transaction from the downstream WCNSS to upstream
MSM at a skbuff address we will have released.

Fixes: 8e84c258 ("wcn36xx: mac80211 driver for Qualcomm WCN3660/WCN3680 hardware")
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20211105122152.1580542-4-bryan.odonoghue@linaro.org

drivers/net/wireless/ath/wcn36xx/dxe.c

@@ -1044,6 +1044,8 @@ int wcn36xx_dxe_init(struct wcn36xx *wcn)
 
 void wcn36xx_dxe_deinit(struct wcn36xx *wcn)
 {
+	int reg_data = 0;
+
 	/* Disable channel interrupts */
 	wcn36xx_dxe_disable_ch_int(wcn, WCN36XX_INT_MASK_CHAN_RX_H);
 	wcn36xx_dxe_disable_ch_int(wcn, WCN36XX_INT_MASK_CHAN_RX_L);
@@ -1059,6 +1061,10 @@ void wcn36xx_dxe_deinit(struct wcn36xx *wcn)
 		wcn->tx_ack_skb = NULL;
 	}
 
+	/* Put the DXE block into reset before freeing memory */
+	reg_data = WCN36XX_DXE_REG_RESET;
+	wcn36xx_dxe_write_register(wcn, WCN36XX_DXE_REG_CSR_RESET, reg_data);
+
 	wcn36xx_dxe_ch_free_skbs(wcn, &wcn->dxe_rx_l_ch);
 	wcn36xx_dxe_ch_free_skbs(wcn, &wcn->dxe_rx_h_ch);