diff options
| author |   David Jander <david@protonic.nl> | 2022-06-21 08:12:25 +0200 |
|---|---|---|
| committer |   Mark Brown <broonie@kernel.org> | 2022-06-27 13:27:17 +0100 |
| commit | ae7d2346dc89ae89a6e0aabe6037591a11e593c0 (patch) | |
| tree | 23155ebdfdee2cf38b3ed9bd918e323c1fcc5ca8 /include/linux/spi | |
| parent | spi: Move ctlr->cur_msg_prepared to struct spi_message (diff) | |
| download | linux-dev-ae7d2346dc89ae89a6e0aabe6037591a11e593c0.tar.xz linux-dev-ae7d2346dc89ae89a6e0aabe6037591a11e593c0.zip | |
spi: Don't use the message queue if possible in spi_sync
The interaction with the controller message queue and its corresponding
auxiliary flags and variables requires the use of the queue_lock which is
costly. Since spi_sync will transfer the complete message anyway, and not
return until it is finished, there is no need to put the message into the
queue if the queue is empty. This can save a lot of overhead.
As an example of how significant this is, when using the MCP2518FD SPI CAN
controller on a i.MX8MM SoC, the time during which the interrupt line
stays active (during 3 relatively short spi_sync messages), is reduced
from 98us to 72us by this patch.
Signed-off-by: David Jander <david@protonic.nl>
Link: https://lore.kernel.org/r/20220621061234.3626638-3-david@protonic.nl
Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'include/linux/spi')
| -rw-r--r-- | include/linux/spi/spi.h | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 1a75c26742f2..74261a83b5fa 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -461,6 +461,8 @@ extern struct spi_device *spi_new_ancillary_device(struct spi_device *spi, u8 ch * @irq_flags: Interrupt enable state during PTP system timestamping * @fallback: fallback to pio if dma transfer return failure with * SPI_TRANS_FAIL_NO_START. + * @queue_empty: signal green light for opportunistically skipping the queue + * for spi_sync transfers. * * Each SPI controller can communicate with one or more @spi_device * children. These make a small bus, sharing MOSI, MISO and SCK signals @@ -677,6 +679,9 @@ struct spi_controller { /* Interrupt enable state during PTP system timestamping */ unsigned long irq_flags; + + /* Flag for enabling opportunistic skipping of the queue in spi_sync */ + bool queue_empty; }; static inline void *spi_controller_get_devdata(struct spi_controller *ctlr) @@ -986,6 +991,7 @@ struct spi_transfer { * @state: for use by whichever driver currently owns the message * @resources: for resource management when the spi message is processed * @prepared: spi_prepare_message was called for the this message + * @sync: this message took the direct sync path skipping the async queue * * A @spi_message is used to execute an atomic sequence of data transfers, * each represented by a struct spi_transfer. The sequence is "atomic" @@ -1037,7 +1043,10 @@ struct spi_message { struct list_head resources; /* spi_prepare_message was called for this message */ - bool prepared; + bool prepared; + + /* this message is skipping the async queue */ + bool sync; }; static inline void spi_message_init_no_memset(struct spi_message *m) |