linux-kernel - [PATCH 2/4] spi: axi-spi-engine: don't repeat mode config for offload

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Message-Id: <20250428-adi-main-v1-2-4b8a1b88a212@baylibre.com>
Date: Mon, 28 Apr 2025 15:58:57 -0500
From: David Lechner <dlechner@...libre.com>
To: Michael Hennerich <michael.hennerich@...log.com>, 
 Nuno Sá <nuno.sa@...log.com>, 
 Mark Brown <broonie@...nel.org>
Cc: linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org, 
 David Lechner <dlechner@...libre.com>
Subject: [PATCH 2/4] spi: axi-spi-engine: don't repeat mode config for
 offload

Add an optimization to avoid repeating the config instruction in each
SPI message when using SPI offloading. Instead, the instruction is
run once when the SPI offload trigger is enabled.

This is done to allow higher sample rates for ADCs using this SPI
controller.

Signed-off-by: David Lechner <dlechner@...libre.com>
---
 drivers/spi/spi-axi-spi-engine.c | 33 ++++++++++++++++++++++++++++++---
 1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi-axi-spi-engine.c b/drivers/spi/spi-axi-spi-engine.c
index d040deffa9bb9bdcb67bcc8af0a1cfad2e4f6041..05ef2589f8dc0bdaa1b3bb3a459670d174f821a2 100644
--- a/drivers/spi/spi-axi-spi-engine.c
+++ b/drivers/spi/spi-axi-spi-engine.c
@@ -141,6 +141,7 @@ struct spi_engine_offload {
 	struct spi_engine *spi_engine;
 	unsigned long flags;
 	unsigned int offload_num;
+	unsigned int spi_mode_config;
 };
 
 struct spi_engine {
@@ -284,6 +285,7 @@ static void spi_engine_compile_message(struct spi_message *msg, bool dry,
 {
 	struct spi_device *spi = msg->spi;
 	struct spi_controller *host = spi->controller;
+	struct spi_engine_offload *priv;
 	struct spi_transfer *xfer;
 	int clk_div, new_clk_div, inst_ns;
 	bool keep_cs = false;
@@ -297,9 +299,18 @@ static void spi_engine_compile_message(struct spi_message *msg, bool dry,
 
 	clk_div = 1;
 
-	spi_engine_program_add_cmd(p, dry,
-		SPI_ENGINE_CMD_WRITE(SPI_ENGINE_CMD_REG_CONFIG,
-			spi_engine_get_config(spi)));
+	/*
+	 * As an optimization, SPI offload sets once this when the offload is
+	 * enabled instead of repeating the instruction in each message.
+	 */
+	if (msg->offload) {
+		priv = msg->offload->priv;
+		priv->spi_mode_config = spi_engine_get_config(spi);
+	} else {
+		spi_engine_program_add_cmd(p, dry,
+			SPI_ENGINE_CMD_WRITE(SPI_ENGINE_CMD_REG_CONFIG,
+				spi_engine_get_config(spi)));
+	}
 
 	xfer = list_first_entry(&msg->transfers, struct spi_transfer, transfer_list);
 	spi_engine_gen_cs(p, dry, spi, !xfer->cs_off);
@@ -842,6 +853,22 @@ static int spi_engine_trigger_enable(struct spi_offload *offload)
 	struct spi_engine_offload *priv = offload->priv;
 	struct spi_engine *spi_engine = priv->spi_engine;
 	unsigned int reg;
+	int ret;
+
+	writel_relaxed(SPI_ENGINE_CMD_SYNC(0),
+		spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);
+
+	writel_relaxed(SPI_ENGINE_CMD_WRITE(SPI_ENGINE_CMD_REG_CONFIG,
+					    priv->spi_mode_config),
+		       spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);
+
+	writel_relaxed(SPI_ENGINE_CMD_SYNC(1),
+		spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);
+
+	ret = readl_relaxed_poll_timeout(spi_engine->base + SPI_ENGINE_REG_SYNC_ID,
+					 reg, reg == 1, 1, 1000);
+	if (ret)
+		return ret;
 
 	reg = readl_relaxed(spi_engine->base +
 			    SPI_ENGINE_REG_OFFLOAD_CTRL(priv->offload_num));

-- 
2.43.0