Re: [PATCH 2/3] Bluetooth: hci_qca: Skip serdev wait when no transfer is pending

From: bgodavar
Date: Sat Jun 06 2020 - 08:58:13 EST


Hi matthias,

On 2020-06-06 00:16, Matthias Kaehlcke wrote:
qca_suspend() calls serdev_device_wait_until_sent() regardless of
whether a transfer is pending. While it does no active harm since
the function should return immediately it makes the code more
confusing. Add a flag to track whether a transfer is pending and
only call serdev_device_wait_until_sent() is needed.

Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
---

drivers/bluetooth/hci_qca.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
index b1d82d32892e9..90ffd8ca1fb0d 100644
--- a/drivers/bluetooth/hci_qca.c
+++ b/drivers/bluetooth/hci_qca.c
@@ -2050,6 +2050,7 @@ static int __maybe_unused qca_suspend(struct device *dev)
struct hci_uart *hu = &qcadev->serdev_hu;
struct qca_data *qca = hu->priv;
unsigned long flags;
+ bool tx_pending = false;
int ret = 0;
u8 cmd;

@@ -2083,6 +2084,7 @@ static int __maybe_unused qca_suspend(struct device *dev)

qca->tx_ibs_state = HCI_IBS_TX_ASLEEP;
qca->ibs_sent_slps++;
+ tx_pending = true;
break;

case HCI_IBS_TX_ASLEEP:
@@ -2099,8 +2101,10 @@ static int __maybe_unused qca_suspend(struct device *dev)
if (ret < 0)
goto error;

- serdev_device_wait_until_sent(hu->serdev,
- msecs_to_jiffies(CMD_TRANS_TIMEOUT_MS));
+ if (tx_pending) {
[Bala]: Good idea why don't we move this call to switch case under HCI_IBS_TX_AWAKE
https://elixir.bootlin.com/linux/latest/source/drivers/bluetooth/hci_qca.c#L1994

i.e. i would recommend below sequence

1. Send SLEEP BYTE
2. wait for some time to write SLEEP Byte on Tx line
3. call for Tx clock off qca_wq_serial_tx_clock_vote_off

+ serdev_device_wait_until_sent(hu->serdev,
+ msecs_to_jiffies(CMD_TRANS_TIMEOUT_MS));
+ }

/* Wait for HCI_IBS_SLEEP_IND sent by device to indicate its Tx is going
* to sleep, so that the packet does not wake the system later.