0038-mediatek-pci-reset.patch

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From:   Kai-Heng Feng <kai.heng.feng@canonical.com>
To:     nbd@nbd.name, lorenzo@kernel.org, ryder.lee@mediatek.com
Cc:     Kai-Heng Feng <kai.heng.feng@canonical.com>,
        Shayne Chen <shayne.chen@mediatek.com>,
        Sean Wang <sean.wang@mediatek.com>,
        Kalle Valo <kvalo@kernel.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        Deren Wu <deren.wu@mediatek.com>,
        Leon Yen <Leon.Yen@mediatek.com>,
        linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org
Subject: [PATCH] wifi: mt76: mt7921e: Perform FLR to recovery the device
Date:   Wed, 14 Jun 2023 14:32:50 +0800
Message-Id: <20230614063252.1650824-1-kai.heng.feng@canonical.com>
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When "Pre-boot WiFi" is enabled in BIOS, the mt7921e device may not
work:
mt7921e 0000:02:00.0: ASIC revision: 79220010
mt7921e 0000:02:00.0: Message 00000010 (seq 1) timeout
mt7921e 0000:02:00.0: Failed to get patch semaphore
mt7921e 0000:02:00.0: Message 00000010 (seq 2) timeout
mt7921e 0000:02:00.0: Failed to get patch semaphore
mt7921e 0000:02:00.0: Message 00000010 (seq 3) timeout
mt7921e 0000:02:00.0: Failed to get patch semaphore
mt7921e 0000:02:00.0: Message 00000010 (seq 4) timeout
mt7921e 0000:02:00.0: Failed to get patch semaphore
mt7921e 0000:02:00.0: Message 00000010 (seq 5) timeout
mt7921e 0000:02:00.0: Failed to get patch semaphore
mt7921e 0000:02:00.0: Message 00000010 (seq 6) timeout
mt7921e 0000:02:00.0: Failed to get patch semaphore
mt7921e 0000:02:00.0: Message 00000010 (seq 7) timeout
mt7921e 0000:02:00.0: Failed to get patch semaphore
mt7921e 0000:02:00.0: Message 00000010 (seq 8) timeout
mt7921e 0000:02:00.0: Failed to get patch semaphore
mt7921e 0000:02:00.0: Message 00000010 (seq 9) timeout
mt7921e 0000:02:00.0: Failed to get patch semaphore
mt7921e 0000:02:00.0: Message 00000010 (seq 10) timeout
mt7921e 0000:02:00.0: Failed to get patch semaphore
mt7921e 0000:02:00.0: hardware init failed

After some trials and errors, it shows that PCI function level reset can
recover the device back to a functional state.

So perform FLR at probe routine to workaround the issue.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
---
 drivers/net/wireless/mediatek/mt76/mt7921/pci.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/pci.c b/drivers/net/wireless/mediatek/mt76/mt7921/pci.c
index ddb1fa4ee01d..9671fbe35a8e 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7921/pci.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7921/pci.c
@@ -262,6 +262,10 @@ static int mt7921_pci_probe(struct pci_dev *pdev,
 	int ret;
 	u16 cmd;
 
+	ret = pci_reset_function_locked(pdev);
+	if (ret)
+		pci_info(pdev, "Unable to perform FLR\n");
+
 	ret = pcim_enable_device(pdev);
 	if (ret)
 		return ret;
-- 
2.34.1