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

On Mon, Jan 21, 2019 at 09:56:13AM +0100, Johan Hovold wrote:

On Fri, Jan 18, 2019 at 04:31:09PM -0800, Matthias Kaehlcke wrote:

quoted

On Fri, Jan 18, 2019 at 10:44:16AM +0100, Johan Hovold wrote:

quoted

On Thu, Jan 17, 2019 at 09:21:09AM -0800, Matthias Kaehlcke wrote:

quoted

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/

Nice (I did mean set_mctrl() above, as I think you noticed).

quoted

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);

Wow, yeah, this parameter inversion is indeed confusing...

quoted

 			serdev_device_set_rts(hu->serdev, false);
+		}

But looking at hci_uart_set_flow_control() now, it actually also
deasserts RTS. So all you need here is the hci_uart_set_flow_control()
call.  

Great, thanks for pointing that out!

And that makes the inversion make a bit more sense too, even if the
naming is a bit unfortunate with respect to
serdev_device_set_flow_control() at least.