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spi: axi-spi-engine: don't emit XFER_BITS for empty xfer

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This adds a check on xfer->len to avoid emitting an XFER_BITS
instruction for empty transfers in the AXI SPI Engine driver. This
avoids unnecessary delays caused by executing an instruction that has
no effect on the actual SPI transfer.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Link: https://patch.msgid.link/20240723-spi-axi-spi-engine-opt-bpw-v1-1-2625ba4c4387@baylibre.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
David Lechner 2024-07-23 13:36:47 -05:00 committed by Mark Brown
parent 8400291e28
commit f8918ef126
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1 changed files with 1 additions and 1 deletions
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2
drivers/spi/spi-axi-spi-engine.c
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@ -258,7 +258,7 @@ static void spi_engine_compile_message(struct spi_message *msg, bool dry,
clk_div - 1));
}
if (bits_per_word != xfer->bits_per_word) {
if (bits_per_word != xfer->bits_per_word && xfer->len) {
bits_per_word = xfer->bits_per_word;
spi_engine_program_add_cmd(p, dry,
SPI_ENGINE_CMD_WRITE(SPI_ENGINE_CMD_REG_XFER_BITS,