linux-kernel - [PATCH] Bluetooth: btqca: Add a short delay before downloading the NVM

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Message-Id: <20190709224450.187737-1-mka@chromium.org>
Date:   Tue,  9 Jul 2019 15:44:50 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>
Cc:     linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org,
        Balakrishna Godavarthi <bgodavar@...eaurora.org>,
        Harish Bandi <c-hbandi@...eaurora.org>,
        Rocky Liao <rjliao@...eaurora.org>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: [PATCH] Bluetooth: btqca: Add a short delay before downloading the NVM

On WCN3990 downloading the NVM sometimes fails with a "TLV response
size mismatch" error:

[  174.949955] Bluetooth: btqca.c:qca_download_firmware() hci0: QCA Downloading qca/crnv21.bin
[  174.958718] Bluetooth: btqca.c:qca_tlv_send_segment() hci0: QCA TLV response size mismatch

It seems the controller needs a short time after downloading the
firmware before it is ready for the NVM. A delay as short as 1 ms
seems sufficient, make it 10 ms just in case. No event is received
during the delay, hence we don't just silently drop an extra event.

Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
---
I'm only guessing why the delay is needed, maybe QCA folks can shed
more light on this.

I didn't see this error when testing 2faa3f15fa2f ("Bluetooth: hci_qca:
wcn3990: Drop baudrate change vendor event") and 32646db8cc28
("Bluetooth: btqca: inject command complete event during fw download")
intensively a few months ago. My guess is that some changes in the kernel
(I test with a 4.19 kernel with regular -stable merges) altered the
timing, which made this issue visible.
---
 drivers/bluetooth/btqca.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/bluetooth/btqca.c b/drivers/bluetooth/btqca.c
index 8b33128dccee..c59ca5782b63 100644
--- a/drivers/bluetooth/btqca.c
+++ b/drivers/bluetooth/btqca.c
@@ -388,6 +388,9 @@ int qca_uart_setup(struct hci_dev *hdev, uint8_t baudrate,
 		return err;
 	}
 
+	/* Give the controller some time to get ready to receive the NVM */
+	msleep(10);
+
 	/* Download NVM configuration */
 	config.type = TLV_TYPE_NVM;
 	if (firmware_name)
-- 
2.22.0.410.gd8fdbe21b5-goog