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spi: add defer_optimize_message controller flag

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Adding spi_optimize_message() broke the spi-mux driver because it
calls spi_async() from it's transfer_one_message() callback. This
resulted in passing an incorrectly optimized message to the controller.
For example, if the underlying controller has an optimize_message()
callback, this would have not been called and can cause a crash when
the underlying controller driver tries to transfer the message.

Also, since the spi-mux driver swaps out the controller pointer by
replacing msg->spi, __spi_unoptimize_message() was being called with a
different controller than the one used in __spi_optimize_message(). This
could cause a crash when attempting to free the message resources when
__spi_unoptimize_message() is called in spi_finalize_current_message()
since it is being called with a controller that did not allocate the
resources.

This is fixed by adding a defer_optimize_message flag for controllers.
This flag causes all of the spi_[maybe_][un]optimize_message() calls to
be a no-op (other than attaching a pointer to the spi device to the
message).

This allows the spi-mux driver to pass an unmodified message to
spi_async() in spi_mux_transfer_one_message() after the spi device has
been swapped out. This causes __spi_optimize_message() and
__spi_unoptimize_message() to be called only once per message and with
the correct/same controller in each case.

Reported-by: Oleksij Rempel <o.rempel@pengutronix.de>
Closes: https://lore.kernel.org/linux-spi/Zn6HMrYG2b7epUxT@pengutronix.de/
Reported-by: Marc Kleine-Budde <mkl@pengutronix.de>
Closes: https://lore.kernel.org/linux-spi/20240628-awesome-discerning-bear-1621f9-mkl@pengutronix.de/
Fixes: 7b1d87af14 ("spi: add spi_optimize_message() APIs")
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20240708-spi-mux-fix-v1-2-6c8845193128@baylibre.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
David Lechner
2024-07-08 20:05:29 -05:00
committed by Mark Brown
parent c86a918b1b
commit ca52aa4c60
3 changed files with 22 additions and 1 deletions
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include/linux/spi/spi.h
+4
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@@ -533,6 +533,9 @@ 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
* @defer_optimize_message: set to true if controller cannot pre-optimize messages
* and needs to defer the optimization step until the message is actually
* being transferred
*
* Each SPI controller can communicate with one or more @spi_device
* children. These make a small bus, sharing MOSI, MISO and SCK signals
@@ -776,6 +779,7 @@ struct spi_controller {
/* Flag for enabling opportunistic skipping of the queue in spi_sync */
bool queue_empty;
bool must_async;
bool defer_optimize_message;
};
static inline void *spi_controller_get_devdata(struct spi_controller *ctlr)