From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Subject: Re: [PATCH v3 3/8] mailbox: Add transmit done by blocking option Date: Mon, 2 Jul 2018 15:09:52 +0200 Message-ID: <20180702130952.GE13096@ulmo> References: <20180702114033.15654-1-mperttunen@nvidia.com> <20180702114033.15654-4-mperttunen@nvidia.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="SNIs70sCzqvszXB4" Return-path: Content-Disposition: inline In-Reply-To: <20180702114033.15654-4-mperttunen@nvidia.com> Sender: linux-kernel-owner@vger.kernel.org To: Mikko Perttunen Cc: jassisinghbrar@gmail.com, gregkh@linuxfoundation.org, jonathanh@nvidia.com, devicetree@vger.kernel.org, linux-serial@vger.kernel.org, linux-tegra@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org List-Id: devicetree@vger.kernel.org --SNIs70sCzqvszXB4 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jul 02, 2018 at 02:40:28PM +0300, Mikko Perttunen wrote: > Add a new TXDONE option, TXDONE_BY_BLOCK. With this option, the > send_data function of the mailbox driver is expected to block until > the message has been sent. The new option is used with the Tegra > Combined UART driver to minimize unnecessary overhead when transmitting > data. >=20 > Signed-off-by: Mikko Perttunen > --- > drivers/mailbox/mailbox.c | 30 +++++++++++++++++++++--------- > drivers/mailbox/mailbox.h | 1 + > 2 files changed, 22 insertions(+), 9 deletions(-) >=20 > diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c > index 674b35f402f5..5c76b70e673c 100644 > --- a/drivers/mailbox/mailbox.c > +++ b/drivers/mailbox/mailbox.c > @@ -53,6 +53,8 @@ static int add_to_rbuf(struct mbox_chan *chan, void *ms= sg) > return idx; > } > =20 > +static void tx_tick(struct mbox_chan *chan, int r, bool submit_next); > + > static void msg_submit(struct mbox_chan *chan) > { > unsigned count, idx; > @@ -60,10 +62,13 @@ static void msg_submit(struct mbox_chan *chan) > void *data; > int err =3D -EBUSY; > =20 > +next: > spin_lock_irqsave(&chan->lock, flags); > =20 > - if (!chan->msg_count || chan->active_req) > - goto exit; > + if (!chan->msg_count || chan->active_req) { > + spin_unlock_irqrestore(&chan->lock, flags); > + return; > + } > =20 > count =3D chan->msg_count; > idx =3D chan->msg_free; > @@ -82,15 +87,21 @@ static void msg_submit(struct mbox_chan *chan) > chan->active_req =3D data; > chan->msg_count--; > } > -exit: > + > spin_unlock_irqrestore(&chan->lock, flags); > =20 > if (!err && (chan->txdone_method & TXDONE_BY_POLL)) > /* kick start the timer immediately to avoid delays */ > hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL); > + > + if (chan->txdone_method & TXDONE_BY_BLOCK) { > + tx_tick(chan, err, false); > + if (!err) > + goto next; > + } This bit is slightly confusing: if check for err, but the call to the tx_tick() function doesn't actually change err (it's passed by value). Now, I don't have any great ideas on how to improve this, but perhaps a simple comment would help clarify what's going on here, or maybe by adding an extra blank line between the tx_tick() call and the conditional would make it more obvious that these aren't related. Also, it looks to me like this is actually modifying msg_submit() to actually do more than just submit the next data from a message. This effectively flushes the complete message via the mailbox, right? Perhaps a slightly clearer implmentation would be to turn this into a separate function that repeatedly calls msg_submit() in a loop or some such. > } > =20 > -static void tx_tick(struct mbox_chan *chan, int r) > +static void tx_tick(struct mbox_chan *chan, int r, bool submit_next) > { > unsigned long flags; > void *mssg; > @@ -101,7 +112,8 @@ static void tx_tick(struct mbox_chan *chan, int r) > spin_unlock_irqrestore(&chan->lock, flags); > =20 > /* Submit next message */ > - msg_submit(chan); > + if (submit_next) > + msg_submit(chan); > =20 > if (!mssg) > return; > @@ -127,7 +139,7 @@ static enum hrtimer_restart txdone_hrtimer(struct hrt= imer *hrtimer) > if (chan->active_req && chan->cl) { > txdone =3D chan->mbox->ops->last_tx_done(chan); > if (txdone) > - tx_tick(chan, 0); > + tx_tick(chan, 0, true); > else > resched =3D true; > } > @@ -176,7 +188,7 @@ void mbox_chan_txdone(struct mbox_chan *chan, int r) > return; > } > =20 > - tx_tick(chan, r); > + tx_tick(chan, r, true); > } > EXPORT_SYMBOL_GPL(mbox_chan_txdone); > =20 > @@ -196,7 +208,7 @@ void mbox_client_txdone(struct mbox_chan *chan, int r) > return; > } > =20 > - tx_tick(chan, r); > + tx_tick(chan, r, true); > } > EXPORT_SYMBOL_GPL(mbox_client_txdone); > =20 > @@ -275,7 +287,7 @@ int mbox_send_message(struct mbox_chan *chan, void *m= ssg) > ret =3D wait_for_completion_timeout(&chan->tx_complete, wait); > if (ret =3D=3D 0) { > t =3D -ETIME; > - tx_tick(chan, t); > + tx_tick(chan, t, true); > } > } > =20 > diff --git a/drivers/mailbox/mailbox.h b/drivers/mailbox/mailbox.h > index 456ba68513bb..ec68e2e28cd6 100644 > --- a/drivers/mailbox/mailbox.h > +++ b/drivers/mailbox/mailbox.h > @@ -10,5 +10,6 @@ > #define TXDONE_BY_IRQ BIT(0) /* controller has remote RTR irq */ > #define TXDONE_BY_POLL BIT(1) /* controller can read status of last TX */ > #define TXDONE_BY_ACK BIT(2) /* S/W ACK recevied by Client ticks the TX = */ > +#define TXDONE_BY_BLOCK BIT(3) /* mailbox driver send_data blocks until = done */ Perhaps clarify here that it blocks until all data in the message has been transmitted. As it is, this could mean just block until the current datum is done transmitting. 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