linux-kernel - Re: [PATCH v5 2/5] Bluetooth: hci_qca: Deassert RTS while baudrate change command

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Message-ID: <20190119003109.GD261387@google.com>
Date:   Fri, 18 Jan 2019 16:31:09 -0800
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     Balakrishna Godavarthi <bgodavar@...eaurora.org>,
        marcel@...tmann.org, johan.hedberg@...il.com,
        linux-kernel@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        hemantg@...eaurora.org, linux-arm-msm@...r.kernel.org,
        Johan Hovold <jhovold@...il.com>
Subject: Re: [PATCH v5 2/5] Bluetooth: hci_qca: Deassert RTS while baudrate
 change command

On Fri, Jan 18, 2019 at 10:44:16AM +0100, Johan Hovold wrote:
> On Thu, Jan 17, 2019 at 09:21:09AM -0800, Matthias Kaehlcke wrote:
> 
> > I observed that the qcom_geni_serial driver doesn't raise RTS with
> > flow control disabled. It seems we have to investigate why that's the
> > case. I agree that the driver should be platform agnostic.
> 
> Sounds like a driver bug, unless the hardware is just "odd". The
> driver implementation of this looks very non-standard judging from a
> quick peek.
> 
> In fact, qcom_geni_serial_get_mctrl() is currently a no-op if hardware
> flow control is not enabled:
> 
> 	if (uart_console(uport) || !uart_cts_enabled(uport))
> 		return;
> 
> Perhaps dropping the !uart_cts_enabled() test is sufficient.

Thanks for taking a look Johan, that was indeed the problem (also
in set_mctrl()). I posted a fix: https://lore.kernel.org/patchwork/patch/1033611/

Balakrishna, the following (applied on top of your patch) works for me
with the UART patch above:

diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
index 9d5e41f159c78f..60bfdf01f72841 100644
--- a/drivers/bluetooth/hci_qca.c
+++ b/drivers/bluetooth/hci_qca.c
@@ -1080,7 +1080,7 @@ static int qca_set_speed(struct hci_uart *hu, enum qca_speed_type speed_type)
 {
 	unsigned int speed, qca_baudrate;
 	struct qca_serdev *qcadev;
-	int ret;
+	int ret = 0;
 
 	if (speed_type == QCA_INIT_SPEED) {
 		speed = qca_get_speed(hu, QCA_INIT_SPEED);
@@ -1097,22 +1097,27 @@ static int qca_set_speed(struct hci_uart *hu, enum qca_speed_type speed_type)
 		 * the old speed.
 		 */
 		qcadev = serdev_device_get_drvdata(hu->serdev);
-		if (qcadev->btsoc_type == QCA_WCN3990)
+		if (qcadev->btsoc_type == QCA_WCN3990) {
+			hci_uart_set_flow_control(hu, true);
 			serdev_device_set_rts(hu->serdev, false);
+		}
 
 		qca_baudrate = qca_get_baudrate_value(speed);
 		bt_dev_dbg(hu->hdev, "Set UART speed to %d", speed);
 		ret = qca_set_baudrate(hu->hdev, qca_baudrate);
 		if (ret)
-			return ret;
+			goto out;
 
 		host_set_baudrate(hu, speed);
 
-		if (qcadev->btsoc_type == QCA_WCN3990)
+out:
+		if (qcadev->btsoc_type == QCA_WCN3990) {
+			hci_uart_set_flow_control(hu, false);
 			serdev_device_set_rts(hu->serdev, true);
+		}
 	}
 
-	return 0;
+	return ret;
 }
 
 static int qca_wcn3990_init(struct hci_uart *hu)