[PATCH 6.8 142/715] spi: move split xfers for CS_WORD emulation

Sasha Levin
2024-03-24T22:37:19Z

From: David Lechner <dlechner@baylibre.com>

[ Upstream commit c8bec3355f08ddb887d5c13b7095dfa79e6db108 ]

This moves splitting transfers for CS_WORD software emulation to the
same place where we split transfers for controller-specific reasons.

This fixes a few subtle bugs.

The calculation for maxsize was wrong for bit sizes between 17 and 24.
This is fixed by making use of spi_split_transfers_maxwords() which
already has the correct calculation.

Also, since this indirectly calls spi_res_alloc(), to avoid leaking
resources, spi_finalize_current_message() would need to be called
on all error paths in __spi_validate() and callers of __spi_validate()
would need to do the same. This is fixed by moving the call to
__spi_pump_transfer_message() where it is already splitting transfers
for other reasons and correctly releases resources in the subsequent
error paths.

Fixes: cbaa62e0094a ("spi: add software implementation for SPI_CS_WORD")
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20240126212358.3916280-2-dlechner@baylibre.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/spi/spi.c | 63 +++++++++++++++++++++++------------------------
1 file changed, 31 insertions(+), 32 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 8dfe635fffd63..d1b297f438f14 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1747,13 +1747,37 @@ static int __spi_pump_transfer_message(struct spi_controller *ctlr,

trace_spi_message_start(msg);

- ret = spi_split_transfers_maxsize(ctlr, msg,
- spi_max_transfer_size(msg->spi),
- GFP_KERNEL | GFP_DMA);
- if (ret) {
- msg->status = ret;
- spi_finalize_current_message(ctlr);
- return ret;
+ /*
+ * If an SPI controller does not support toggling the CS line on each
+ * transfer (indicated by the SPI_CS_WORD flag) or we are using a GPIO
+ * for the CS line, we can emulate the CS-per-word hardware function by
+ * splitting transfers into one-word transfers and ensuring that
+ * cs_change is set for each transfer.
+ */
+ if ((msg->spi->mode & SPI_CS_WORD) && (!(ctlr->mode_bits & SPI_CS_WORD) ||
+ spi_is_csgpiod(msg->spi))) {
+ ret = spi_split_transfers_maxwords(ctlr, msg, 1, GFP_KERNEL);
+ if (ret) {
+ msg->status = ret;
+ spi_finalize_current_message(ctlr);
+ return ret;
+ }
+
+ list_for_each_entry(xfer, &msg->transfers, transfer_list) {
+ /* Don't change cs_change on the last entry in the list */
+ if (list_is_last(&xfer->transfer_list, &msg->transfers))
+ break;
+ xfer->cs_change = 1;
+ }
+ } else {
+ ret = spi_split_transfers_maxsize(ctlr, msg,
+ spi_max_transfer_size(msg->spi),
+ GFP_KERNEL | GFP_DMA);
+ if (ret) {
+ msg->status = ret;
+ spi_finalize_current_message(ctlr);
+ return ret;
+ }
}

if (ctlr->prepare_message) {
@@ -4065,31 +4089,6 @@ static int __spi_validate(struct spi_device *spi, struct spi_message *message)

message->spi = spi;

- /*
- * If an SPI controller does not support toggling the CS line on each
- * transfer (indicated by the SPI_CS_WORD flag) or we are using a GPIO
- * for the CS line, we can emulate the CS-per-word hardware function by
- * splitting transfers into one-word transfers and ensuring that
- * cs_change is set for each transfer.
- */
- if ((spi->mode & SPI_CS_WORD) && (!(ctlr->mode_bits & SPI_CS_WORD) ||
- spi_is_csgpiod(spi))) {
- size_t maxsize = BITS_TO_BYTES(spi->bits_per_word);
- int ret;
-
- ret = spi_split_transfers_maxsize(ctlr, message, maxsize,
- GFP_KERNEL);
- if (ret)
- return ret;
-
- list_for_each_entry(xfer, &message->transfers, transfer_list) {
- /* Don't change cs_change on the last entry in the list */
- if (list_is_last(&xfer->transfer_list, &message->transfers))
- break;
- xfer->cs_change = 1;
- }
- }
-
/*
* Half-duplex links include original MicroWire, and ones with
* only one data pin like SPI_3WIRE (switches direction) or where
--
2.43.0