Re: [PATCH v2 2/3] Bluetooth: hci_qca: Deassert RTS while baudrate change command

From: Balakrishna Godavarthi
Date: Tue Nov 27 2018 - 01:41:15 EST

Hi Matthias,

On 2018-11-27 01:12, Matthias Kaehlcke wrote:
On Thu, Nov 22, 2018 at 05:45:11PM +0530, Balakrishna Godavarthi wrote:
This patch will help to stop frame reassembly errors while changing
the baudrate. This is because host send a change baudrate request
command to the chip with 115200 bps, Whereas chip will change their
UART clocks to the enable for new baudrate and sends the response
for the change request command with newer baudrate, On host side
we are still operating in 115200 bps which results of reading garbage
data. Here we are pulling RTS line, so that chip we will wait to send data
to host until host change its baudrate.

Thanks for updating the commit message and provide more details!

Signed-off-by: Balakrishna Godavarthi <bgodavar@xxxxxxxxxxxxxx>
Tested-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
* updated commit text and comments.
* initial patch
drivers/bluetooth/hci_qca.c | 23 ++++++++++++-----------
1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
index f5dd323c1967..ed905ea1c58a 100644
--- a/drivers/bluetooth/hci_qca.c
+++ b/drivers/bluetooth/hci_qca.c
@@ -963,7 +963,6 @@ static int qca_set_baudrate(struct hci_dev *hdev, uint8_t baudrate)
struct hci_uart *hu = hci_get_drvdata(hdev);
struct qca_data *qca = hu->priv;
struct sk_buff *skb;
- struct qca_serdev *qcadev;
u8 cmd[] = { 0x01, 0x48, 0xFC, 0x01, 0x00 };

if (baudrate > QCA_BAUDRATE_3200000)
@@ -977,13 +976,6 @@ static int qca_set_baudrate(struct hci_dev *hdev, uint8_t baudrate)
return -ENOMEM;

- /* Disabling hardware flow control is mandatory while
- * sending change baudrate request to wcn3990 SoC.
- */
- qcadev = serdev_device_get_drvdata(hu->serdev);
- if (qcadev->btsoc_type == QCA_WCN3990)
- hci_uart_set_flow_control(hu, true);
/* Assign commands to change baudrate and packet type. */
skb_put_data(skb, cmd, sizeof(cmd));
hci_skb_pkt_type(skb) = HCI_COMMAND_PKT;
@@ -999,9 +991,6 @@ static int qca_set_baudrate(struct hci_dev *hdev, uint8_t baudrate)

- if (qcadev->btsoc_type == QCA_WCN3990)
- hci_uart_set_flow_control(hu, false);
return 0;

@@ -1086,6 +1075,7 @@ static int qca_check_speeds(struct hci_uart *hu)
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;

if (speed_type == QCA_INIT_SPEED) {
@@ -1097,6 +1087,14 @@ static int qca_set_speed(struct hci_uart *hu, enum qca_speed_type speed_type)
if (!speed)
return 0;

+ /* Deassert RTS while changing the baudrate of chip and host.
+ * This will stop chip to transmit it response with an newer
+ * baudrate until we change the baudarte.

nit: baudrate

re-nit (to consider if you respin anyway): 'This prevents the chip
from transmitting its response with the new baudrate while the host
port is still operating at the old speed'?
(I'm not a native English speaker, probably there is still room for
improvement ;-)

[Bala]: will update.

Reviewed-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>