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| author | David Jander <david@protonic.nl> | 2022-06-21 08:12:34 +0200 |
|---|---|---|
| committer | Mark Brown <broonie@kernel.org> | 2022-06-27 13:27:26 +0100 |
| commit | dc3029056b02414c29b6627e3dd7b16624725ae9 (patch) | |
| tree | 64225ab8af02e3275de5a0bb8bbf358d1a240680 /include/linux/spi | |
| parent | 69fa95905d40846756d22402690ddf5361a9d13b (diff) | |
| download | linux-stable-dc3029056b02414c29b6627e3dd7b16624725ae9.tar.gz linux-stable-dc3029056b02414c29b6627e3dd7b16624725ae9.tar.bz2 linux-stable-dc3029056b02414c29b6627e3dd7b16624725ae9.zip | |
spi: opportunistically skip ctlr->cur_msg_completion
There are only a few drivers that do not call
spi_finalize_current_message() in the context of transfer_one_message(),
and even for those cases the completion ctlr->cur_msg_completion is not
needed always. The calls to complete() and wait_for_completion() each
take a spin-lock, which is costly. This patch makes it possible to avoid
those calls in the big majority of cases, by introducing two flags that
with the help of ordering via barriers can avoid using the completion
safely. In case of a race with the context calling
spi_finalize_current_message(), the scheme errs on the safe side and takes
the completion.
The impact of this patch is worth the effort: On a i.MX8MM SoC, the time
the SPI bus is idle between two consecutive calls to spi_sync(), is
reduced from 19.6us to 16.8us... roughly 15%.
Signed-off-by: David Jander <david@protonic.nl>
Link: https://lore.kernel.org/r/20220621061234.3626638-12-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 | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index c56e0d240a58..eb0d316e3c36 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -385,6 +385,12 @@ extern struct spi_device *spi_new_ancillary_device(struct spi_device *spi, u8 ch * @queue: message queue * @cur_msg: the currently in-flight message * @cur_msg_completion: a completion for the current in-flight message + * @cur_msg_incomplete: Flag used internally to opportunistically skip + * the @cur_msg_completion. This flag is used to check if the driver has + * already called spi_finalize_current_message(). + * @cur_msg_need_completion: Flag used internally to opportunistically skip + * the @cur_msg_completion. This flag is used to signal the context that + * is running spi_finalize_current_message() that it needs to complete() * @cur_msg_mapped: message has been mapped for DMA * @last_cs: the last chip_select that is recorded by set_cs, -1 on non chip * selected @@ -617,6 +623,8 @@ struct spi_controller { struct list_head queue; struct spi_message *cur_msg; struct completion cur_msg_completion; + bool cur_msg_incomplete; + bool cur_msg_need_completion; bool busy; bool running; bool rt; |