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

From: Balakrishna Godavarthi
Date: Thu Jan 10 2019 - 09:34:28 EST


Hi Johan,

On 2019-01-09 20:22, Johan Hovold wrote:
On Thu, Dec 20, 2018 at 08:16:36PM +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.

Signed-off-by: Balakrishna Godavarthi <bgodavar@xxxxxxxxxxxxxx>
Tested-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
Reviewed-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
---
drivers/bluetooth/hci_qca.c | 24 +++++++++++++-----------
1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
index 5a07c2370289..1680ead6cc3d 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)
schedule_timeout(msecs_to_jiffies(BAUDRATE_SETTLE_TIMEOUT_MS));
set_current_state(TASK_RUNNING);

- 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 +1087,15 @@ 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 prevent chip from transmitting its response with
+ * the new baudrate while the host port is still operating at
+ * the old speed.
+ */
+ qcadev = serdev_device_get_drvdata(hu->serdev);
+ if (qcadev->btsoc_type == QCA_WCN3990)
+ serdev_device_set_rts(hu->serdev, false);
+

This may not do what you want unless you also disable hardware flow
control.

Johan


Here my requirement here is to block the chip to send its data before HOST changes
it is baudrate. So if i disable flow control lines of HOST which will be in low state.
so that the chip will send it data before HOST change the baudrate of HOST. which results in
frame reassembly error.

--
Regards
Balakrishna.