linux-kernel - Re: [PATCH 1/3] Bluetooth: hci_qca: Only remove TX clock vote after TX is completed

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Message-ID: <20200606152632.GR4525@google.com>
Date:   Sat, 6 Jun 2020 08:26:32 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     bgodavar@...eaurora.org
Cc:     Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        linux-bluetooth@...r.kernel.org,
        Rocky Liao <rjliao@...eaurora.org>,
        Zijun Hu <zijuhu@...eaurora.org>, linux-kernel@...r.kernel.org,
        Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
        Claire Chang <tientzu@...omium.org>
Subject: Re: [PATCH 1/3] Bluetooth: hci_qca: Only remove TX clock vote after
 TX is completed

Hi Bala,

On Sat, Jun 06, 2020 at 06:23:13PM +0530, bgodavar@...eaurora.org wrote:
> Hi Matthias,
> 
> On 2020-06-06 00:16, Matthias Kaehlcke wrote:
> > qca_suspend() removes the vote for the UART TX clock after
> > writing an IBS sleep request to the serial buffer. This is
> > not a good idea since there is no guarantee that the request
> > has been sent at this point. Instead remove the vote after
> > successfully entering IBS sleep. This also fixes the issue
> > of the vote being removed in case of an aborted suspend due
> > to a failure of entering IBS sleep.
> > 
> > Fixes: 41d5b25fed0a0 ("Bluetooth: hci_qca: add PM support")
> > Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> > ---
> > 
> >  drivers/bluetooth/hci_qca.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> > index ece9f91cc3deb..b1d82d32892e9 100644
> > --- a/drivers/bluetooth/hci_qca.c
> > +++ b/drivers/bluetooth/hci_qca.c
> > @@ -2083,8 +2083,6 @@ static int __maybe_unused qca_suspend(struct
> > device *dev)
> > 
> >  		qca->tx_ibs_state = HCI_IBS_TX_ASLEEP;
> >  		qca->ibs_sent_slps++;
> > -
> > -		qca_wq_serial_tx_clock_vote_off(&qca->ws_tx_vote_off);
> >  		break;
> > 
> >  	case HCI_IBS_TX_ASLEEP:
> > @@ -2112,8 +2110,10 @@ static int __maybe_unused qca_suspend(struct
> > device *dev)
> >  			qca->rx_ibs_state == HCI_IBS_RX_ASLEEP,
> >  			msecs_to_jiffies(IBS_BTSOC_TX_IDLE_TIMEOUT_MS));
> > 
> > -	if (ret > 0)
> > +	if (ret > 0) {
> > +		qca_wq_serial_tx_clock_vote_off(&qca->ws_tx_vote_off);
> [Bala]: qca_wq_serial_tx_clock_vote_off votes for Tx clock off, when both Tx
> clock and Rx clock voted to off.
> then only actual call to clock off is called.
> https://elixir.bootlin.com/linux/latest/source/drivers/bluetooth/hci_qca.c#L312
> I would recommend to vote Tx clock off after sending SLEEP BYTE from HOST TO
> BT SOC.

Are you suggesting to move the vote after _wait_until_sent() and before
waiting for RX_SLEEP?

I think if the vote is done before RX_SLEEP and going to RX_SLEEP fails the
variables qca->tx_vote and qca->tx_votes_off would have the wrong state, even
if that doesn't lead to actually switching the clock off. I might be missing
something though, I'm not very familiar with this part.