Unverified Commit 087591c9 authored by David Lechner's avatar David Lechner Committed by Mark Brown
Browse files

spi: axi-spi-engine: optimize bits_per_word for offload 



Add an optimization to avoid repeating bits_per_word instructions in
each message when using SPI offload. This only applies when all data
xfers in a message have the same bits_per_word. In this case, we can
execute the instruction that sets bits_per_word when the offload trigger
is enabled. This is useful e.g. for obtaining higher sample rates on
ADCs since each message takes less time to execute.

Signed-off-by: default avatarDavid Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20250428-adi-main-v1-3-4b8a1b88a212@baylibre.com


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 8fc13b82

drivers/spi/spi-axi-spi-engine.c

+32 −0
Original line number Diff line number Diff line
@@ -142,6 +142,7 @@ struct spi_engine_offload { 
	unsigned long flags;

	unsigned int offload_num;

	unsigned int spi_mode_config;

	u8 bits_per_word;

};



struct spi_engine {
@@ -267,6 +268,8 @@ static int spi_engine_precompile_message(struct spi_message *msg) 
{

	unsigned int clk_div, max_hz = msg->spi->controller->max_speed_hz;

	struct spi_transfer *xfer;

	u8 min_bits_per_word = U8_MAX;

	u8 max_bits_per_word = 0;



	list_for_each_entry(xfer, &msg->transfers, transfer_list) {

		/* If we have an offload transfer, we can't rx to buffer */
@@ -275,6 +278,24 @@ static int spi_engine_precompile_message(struct spi_message *msg) 


		clk_div = DIV_ROUND_UP(max_hz, xfer->speed_hz);

		xfer->effective_speed_hz = max_hz / min(clk_div, 256U);



		if (xfer->len) {

			min_bits_per_word = min(min_bits_per_word, xfer->bits_per_word);

			max_bits_per_word = max(max_bits_per_word, xfer->bits_per_word);

		}

	}



	/*

	 * If all xfers in the message use the same bits_per_word, we can

	 * provide some optimization when using SPI offload.

	 */

	if (msg->offload) {

		struct spi_engine_offload *priv = msg->offload->priv;



		if (min_bits_per_word == max_bits_per_word)

			priv->bits_per_word = min_bits_per_word;

		else

			priv->bits_per_word = 0;

	}



	return 0;
@@ -306,6 +327,12 @@ static void spi_engine_compile_message(struct spi_message *msg, bool dry, 
	if (msg->offload) {

		priv = msg->offload->priv;

		priv->spi_mode_config = spi_engine_get_config(spi);



		/*

		 * If all xfers use the same bits_per_word, it can be optimized

		 * in the same way.

		 */

		bits_per_word = priv->bits_per_word;

	} else {

		spi_engine_program_add_cmd(p, dry,

			SPI_ENGINE_CMD_WRITE(SPI_ENGINE_CMD_REG_CONFIG,
@@ -862,6 +889,11 @@ static int spi_engine_trigger_enable(struct spi_offload *offload) 
					    priv->spi_mode_config),

		       spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);



	if (priv->bits_per_word)

		writel_relaxed(SPI_ENGINE_CMD_WRITE(SPI_ENGINE_CMD_REG_XFER_BITS,

						    priv->bits_per_word),

			       spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);



	writel_relaxed(SPI_ENGINE_CMD_SYNC(1),

		spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);