path: root/include/linux/spi/spi.h
diff options
authorMark Brown <broonie@kernel.org>2022-09-01 13:07:32 +0100
committerMark Brown <broonie@kernel.org>2022-09-02 13:27:13 +0100
commitb30f7c8eb0780e1479a9882526e838664271f4c9 (patch)
treedcbf87a782bbd831335e22f59862265517673c32 /include/linux/spi/spi.h
parentspi: cadence-quadspi: Disable irqs during indirect reads (diff)
spi: mux: Fix mux interaction with fast path optimisations
The spi-mux driver is rather too clever and attempts to resubmit any message that is submitted to it to the parent controller with some adjusted callbacks. This does not play at all nicely with the fast path which now sets flags on the message indicating that it's being handled through the fast path, we see async messages flagged as being on the fast path. Ideally the spi-mux code would duplicate the message but that's rather invasive and a bit fragile in that it relies on the mux knowing which fields in the message to copy. Instead teach the core that there are controllers which can't cope with the fast path and have the mux flag itself as being such a controller, ensuring that messages going via the mux don't get partially handled via the fast path. This will reduce the performance of any spi-mux connected device since we'll now always use the thread for both the actual controller and the mux controller instead of just the actual controller but given that we were always hitting the slow path anyway it's hopefully not too much of an additional cost and it allows us to keep the fast path. Fixes: ae7d2346dc89 ("spi: Don't use the message queue if possible in spi_sync") Reported-by: Casper Andersson <casper.casan@gmail.com> Tested-by: Casper Andersson <casper.casan@gmail.com> Signed-off-by: Mark Brown <broonie@kernel.org> Link: https://lore.kernel.org/r/20220901120732.49245-1-broonie@kernel.org Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to '')
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index e6c73d5ff1a8..f089ee1ead58 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -469,6 +469,7 @@ extern struct spi_device *spi_new_ancillary_device(struct spi_device *spi, u8 ch
* @queue_empty: signal green light for opportunistically skipping the queue
* for spi_sync transfers.
+ * @must_async: disable all fast paths in the core
* Each SPI controller can communicate with one or more @spi_device
* children. These make a small bus, sharing MOSI, MISO and SCK signals
@@ -690,6 +691,7 @@ struct spi_controller {
/* Flag for enabling opportunistic skipping of the queue in spi_sync */
bool queue_empty;
+ bool must_async;
static inline void *spi_controller_get_devdata(struct spi_controller *ctlr)