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([2001:a61:3456:4e01:6ae:b55a:bd1d:57fc]) by smtp.gmail.com with ESMTPSA id x19-20020a1709065ad300b00a3e786d8729sm2338011ejs.168.2024.02.20.02.50.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Feb 2024 02:50:40 -0800 (PST) Message-ID: <42bc659ddda05f3d4ece7e4a65e4548da17d17ad.camel@gmail.com> Subject: Re: [PATCH v2 1/5] spi: add spi_optimize_message() APIs From: Nuno =?ISO-8859-1?Q?S=E1?= To: David Lechner , Mark Brown Cc: Martin Sperl , David Jander , Jonathan Cameron , Michael Hennerich , Nuno =?ISO-8859-1?Q?S=E1?= , Alain Volmat , Maxime Coquelin , Alexandre Torgue , linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-iio@vger.kernel.org Date: Tue, 20 Feb 2024 11:50:40 +0100 In-Reply-To: <20240219-mainline-spi-precook-message-v2-1-4a762c6701b9@baylibre.com> References: <20240219-mainline-spi-precook-message-v2-0-4a762c6701b9@baylibre.com> <20240219-mainline-spi-precook-message-v2-1-4a762c6701b9@baylibre.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.3 (3.50.3-1.fc39) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2024-02-19 at 16:33 -0600, David Lechner wrote: > This adds a new spi_optimize_message() function that can be used to > optimize SPI messages that are used more than once. Peripheral drivers > that use the same message multiple times can use this API to perform SPI > message validation and controller-specific optimizations once and then > reuse the message while avoiding the overhead of revalidating the > message on each spi_(a)sync() call. >=20 > Internally, the SPI core will also call this function for each message > if the peripheral driver did not explicitly call it. This is done to so > that controller drivers don't have to have multiple code paths for > optimized and non-optimized messages. >=20 > A hook is provided for controller drivers to perform controller-specific > optimizations. >=20 > Suggested-by: Martin Sperl > Link: > https://lore.kernel.org/linux-spi/39DEC004-10A1-47EF-9D77-276188D2580C@ma= rtin.sperl.org/ > Signed-off-by: David Lechner > --- Acked-by: Nuno Sa >=20 > v2 changes: > - Removed pre_optimized parameter from __spi_optimize_message() > - Added comment explaining purpose of pre_optimized flag > - Fixed missing doc comment for @pre_optimized > - Removed kernel doc inclusion (/** -> /*) from static members > - Removed unrelated comment about calling spi_finalize_current_message() >=20 > =C2=A0drivers/spi/spi.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 | 151 +++++++= +++++++++++++++++++++++++++++++++++++++-- > =C2=A0include/linux/spi/spi.h |=C2=A0 20 +++++++ > =C2=A02 files changed, 167 insertions(+), 4 deletions(-) >=20 > diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c > index c2b10e2c75f0..f68d92b57543 100644 > --- a/drivers/spi/spi.c > +++ b/drivers/spi/spi.c > @@ -2106,6 +2106,41 @@ struct spi_message *spi_get_next_queued_message(st= ruct > spi_controller *ctlr) > =C2=A0} > =C2=A0EXPORT_SYMBOL_GPL(spi_get_next_queued_message); > =C2=A0 > +/* > + * __spi_unoptimize_message - shared implementation of spi_unoptimize_me= ssage() > + *=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0 and spi_maybe_unoptimize_message() > + * @msg: the message to unoptimize > + * > + * Peripheral drivers should use spi_unoptimize_message() and callers in= side > + * core should use spi_maybe_unoptimize_message() rather than calling th= is > + * function directly. > + * > + * It is not valid to call this on a message that is not currently optim= ized. > + */ > +static void __spi_unoptimize_message(struct spi_message *msg) > +{ > + struct spi_controller *ctlr =3D msg->spi->controller; > + > + if (ctlr->unoptimize_message) > + ctlr->unoptimize_message(msg); > + > + msg->optimized =3D false; > + msg->opt_state =3D NULL; > +} > + > +/* > + * spi_maybe_unoptimize_message - unoptimize msg not managed by a periph= eral > + * @msg: the message to unoptimize > + * > + * This function is used to unoptimize a message if and only if it was > + * optimized by the core (via spi_maybe_optimize_message()). > + */ > +static void spi_maybe_unoptimize_message(struct spi_message *msg) > +{ > + if (!msg->pre_optimized && msg->optimized) > + __spi_unoptimize_message(msg); > +} > + > =C2=A0/** > =C2=A0 * spi_finalize_current_message() - the current message is complete > =C2=A0 * @ctlr: the controller to return the message to > @@ -2153,6 +2188,8 @@ void spi_finalize_current_message(struct spi_contro= ller > *ctlr) > =C2=A0 > =C2=A0 mesg->prepared =3D false; > =C2=A0 > + spi_maybe_unoptimize_message(mesg); > + > =C2=A0 WRITE_ONCE(ctlr->cur_msg_incomplete, false); > =C2=A0 smp_mb(); /* See __spi_pump_transfer_message()... */ > =C2=A0 if (READ_ONCE(ctlr->cur_msg_need_completion)) > @@ -4194,6 +4231,110 @@ static int __spi_validate(struct spi_device *spi,= struct > spi_message *message) > =C2=A0 return 0; > =C2=A0} > =C2=A0 > +/* > + * __spi_optimize_message - shared implementation for spi_optimize_messa= ge() > + *=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0 and spi_maybe_optimize_message() > + * @spi: the device that will be used for the message > + * @msg: the message to optimize > + * > + * Peripheral drivers will call spi_optimize_message() and the spi core = will > + * call spi_maybe_optimize_message() instead of calling this directly. > + * > + * It is not valid to call this on a message that has already been optim= ized. > + * > + * Return: zero on success, else a negative error code > + */ > +static int __spi_optimize_message(struct spi_device *spi, > + =C2=A0 struct spi_message *msg) > +{ > + struct spi_controller *ctlr =3D spi->controller; > + int ret; > + > + ret =3D __spi_validate(spi, msg); > + if (ret) > + return ret; > + > + if (ctlr->optimize_message) { > + ret =3D ctlr->optimize_message(msg); > + if (ret) > + return ret; > + } > + > + msg->optimized =3D true; > + > + return 0; > +} > + > +/* > + * spi_maybe_optimize_message - optimize message if it isn't already pre= -optimized > + * @spi: the device that will be used for the message > + * @msg: the message to optimize > + * Return: zero on success, else a negative error code > + */ > +static int spi_maybe_optimize_message(struct spi_device *spi, > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 struct spi_message *msg) > +{ > + if (msg->pre_optimized) > + return 0; > + > + return __spi_optimize_message(spi, msg); > +} > + > +/** > + * spi_optimize_message - do any one-time validation and setup for a SPI= message > + * @spi: the device that will be used for the message > + * @msg: the message to optimize > + * > + * Peripheral drivers that reuse the same message repeatedly may call th= is to > + * perform as much message prep as possible once, rather than repeating = it each > + * time a message transfer is performed to improve throughput and reduce= CPU > + * usage. > + * > + * Once a message has been optimized, it cannot be modified with the exc= eption > + * of updating the contents of any xfer->tx_buf (the pointer can't be ch= anged, > + * only the data in the memory it points to). > + * > + * Calls to this function must be balanced with calls to spi_unoptimize_= message() > + * to avoid leaking resources. > + * > + * Context: can sleep > + * Return: zero on success, else a negative error code > + */ > +int spi_optimize_message(struct spi_device *spi, struct spi_message *msg= ) > +{ > + int ret; > + > + ret =3D __spi_optimize_message(spi, msg); > + if (ret) > + return ret; > + > + /* > + * This flag indicates that the peripheral driver called > spi_optimize_message() > + * and therefore we shouldn't unoptimize message automatically when > finalizing > + * the message but rather wait until spi_unoptimize_message() is called > + * by the peripheral driver. > + */ > + msg->pre_optimized =3D true; > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(spi_optimize_message); > + > +/** > + * spi_unoptimize_message - releases any resources allocated by > spi_optimize_message() > + * @msg: the message to unoptimize > + * > + * Calls to this function must be balanced with calls to spi_optimize_me= ssage(). > + * > + * Context: can sleep > + */ > +void spi_unoptimize_message(struct spi_message *msg) > +{ > + __spi_unoptimize_message(msg); > + msg->pre_optimized =3D false; > +} > +EXPORT_SYMBOL_GPL(spi_unoptimize_message); > + > =C2=A0static int __spi_async(struct spi_device *spi, struct spi_message *= message) > =C2=A0{ > =C2=A0 struct spi_controller *ctlr =3D spi->controller; > @@ -4258,8 +4399,8 @@ int spi_async(struct spi_device *spi, struct spi_me= ssage > *message) > =C2=A0 int ret; > =C2=A0 unsigned long flags; > =C2=A0 > - ret =3D __spi_validate(spi, message); > - if (ret !=3D 0) > + ret =3D spi_maybe_optimize_message(spi, message); > + if (ret) > =C2=A0 return ret; > =C2=A0 > =C2=A0 spin_lock_irqsave(&ctlr->bus_lock_spinlock, flags); > @@ -4271,6 +4412,8 @@ int spi_async(struct spi_device *spi, struct spi_me= ssage > *message) > =C2=A0 > =C2=A0 spin_unlock_irqrestore(&ctlr->bus_lock_spinlock, flags); > =C2=A0 > + spi_maybe_unoptimize_message(message); > + > =C2=A0 return ret; > =C2=A0} > =C2=A0EXPORT_SYMBOL_GPL(spi_async); > @@ -4331,8 +4474,8 @@ static int __spi_sync(struct spi_device *spi, struc= t > spi_message *message) > =C2=A0 return -ESHUTDOWN; > =C2=A0 } > =C2=A0 > - status =3D __spi_validate(spi, message); > - if (status !=3D 0) > + status =3D spi_maybe_optimize_message(spi, message); > + if (status) > =C2=A0 return status; > =C2=A0 > =C2=A0 SPI_STATISTICS_INCREMENT_FIELD(ctlr->pcpu_statistics, spi_sync); > diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h > index 2b8e2746769a..ddfb66dd4caf 100644 > --- a/include/linux/spi/spi.h > +++ b/include/linux/spi/spi.h > @@ -475,6 +475,8 @@ extern struct spi_device *spi_new_ancillary_device(st= ruct > spi_device *spi, u8 ch > =C2=A0 * > =C2=A0 * @set_cs: set the logic level of the chip select line.=C2=A0 May = be called > =C2=A0 *=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 from inter= rupt context. > + * @optimize_message: optimize the message for reuse > + * @unoptimize_message: release resources allocated by optimize_message > =C2=A0 * @prepare_message: set up the controller to transfer a single mes= sage, > =C2=A0 *=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 for example doing DMA mapping= =C2=A0 Called from threaded > =C2=A0 *=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 context. > @@ -715,6 +717,8 @@ struct spi_controller { > =C2=A0 struct completion=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 xfer_completion; > =C2=A0 size_t max_dma_len; > =C2=A0 > + int (*optimize_message)(struct spi_message *msg); > + int (*unoptimize_message)(struct spi_message *msg); > =C2=A0 int (*prepare_transfer_hardware)(struct spi_controller *ctlr); > =C2=A0 int (*transfer_one_message)(struct spi_controller *ctlr, > =C2=A0 =C2=A0=C2=A0=C2=A0 struct spi_message *mesg); > @@ -1111,6 +1115,8 @@ struct spi_transfer { > =C2=A0 * @spi: SPI device to which the transaction is queued > =C2=A0 * @is_dma_mapped: if true, the caller provided both DMA and CPU vi= rtual > =C2=A0 * addresses for each transfer buffer > + * @pre_optimized: peripheral driver pre-optimized the message > + * @optimized: the message is in the optimized state > =C2=A0 * @prepared: spi_prepare_message was called for the this message > =C2=A0 * @status: zero for success, else negative errno > =C2=A0 * @complete: called to report transaction completions > @@ -1120,6 +1126,7 @@ struct spi_transfer { > =C2=A0 * successful segments > =C2=A0 * @queue: for use by whichever driver currently owns the message > =C2=A0 * @state: for use by whichever driver currently owns the message > + * @opt_state: for use by whichever driver currently owns the message > =C2=A0 * @resources: for resource management when the SPI message is proc= essed > =C2=A0 * > =C2=A0 * A @spi_message is used to execute an atomic sequence of data tra= nsfers, > @@ -1143,6 +1150,11 @@ struct spi_message { > =C2=A0 > =C2=A0 unsigned is_dma_mapped:1; > =C2=A0 > + /* spi_optimize_message() was called for this message */ > + bool pre_optimized; > + /* __spi_optimize_message() was called for this message */ > + bool optimized; > + > =C2=A0 /* spi_prepare_message() was called for this message */ > =C2=A0 bool prepared; > =C2=A0 > @@ -1172,6 +1184,11 @@ struct spi_message { > =C2=A0 */ > =C2=A0 struct list_head queue; > =C2=A0 void *state; > + /* > + * Optional state for use by controller driver between calls to > + * __spi_optimize_message() and __spi_unoptimize_message(). > + */ > + void *opt_state; > =C2=A0 > =C2=A0 /* List of spi_res resources when the SPI message is processed */ > =C2=A0 struct list_head=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 resourc= es; > @@ -1255,6 +1272,9 @@ static inline void spi_message_free(struct spi_mess= age *m) > =C2=A0 kfree(m); > =C2=A0} > =C2=A0 > +extern int spi_optimize_message(struct spi_device *spi, struct spi_messa= ge *msg); > +extern void spi_unoptimize_message(struct spi_message *msg); > + > =C2=A0extern int spi_setup(struct spi_device *spi); > =C2=A0extern int spi_async(struct spi_device *spi, struct spi_message *me= ssage); > =C2=A0extern int spi_slave_abort(struct spi_device *spi); >=20