3 files changed, 36 insertions, 11 deletions

diff --git a/drivers/spi/spi-axi-spi-engine.c b/drivers/spi/spi-axi-spi-engine.c
index e358ac5b45..96a5247725 100644
--- a/drivers/spi/spi-axi-spi-engine.c
+++ b/drivers/spi/spi-axi-spi-engine.c
@@ -164,16 +164,20 @@ static void spi_engine_gen_xfer(struct spi_engine_program *p, bool dry,
 }
 
 static void spi_engine_gen_sleep(struct spi_engine_program *p, bool dry,
-				 int delay_ns, u32 sclk_hz)
+				 int delay_ns, int inst_ns, u32 sclk_hz)
 {
 	unsigned int t;
 
-	/* negative delay indicates error, e.g. from spi_delay_to_ns() */
-	if (delay_ns <= 0)
+	/*
+	 * Negative delay indicates error, e.g. from spi_delay_to_ns(). And if
+	 * delay is less that the instruction execution time, there is no need
+	 * for an extra sleep instruction since the instruction execution time
+	 * will already cover the required delay.
+	 */
+	if (delay_ns < 0 || delay_ns <= inst_ns)
 		return;
 
-	/* rounding down since executing the instruction adds a couple of ticks delay */
-	t = DIV_ROUND_DOWN_ULL((u64)delay_ns * sclk_hz, NSEC_PER_SEC);
+	t = DIV_ROUND_UP_ULL((u64)(delay_ns - inst_ns) * sclk_hz, NSEC_PER_SEC);
 	while (t) {
 		unsigned int n = min(t, 256U);
 
@@ -220,10 +224,16 @@ 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_transfer *xfer;
-	int clk_div, new_clk_div;
+	int clk_div, new_clk_div, inst_ns;
 	bool keep_cs = false;
 	u8 bits_per_word = 0;
 
+	/*
+	 * Take into account instruction execution time for more accurate sleep
+	 * times, especially when the delay is small.
+	 */
+	inst_ns = DIV_ROUND_UP(NSEC_PER_SEC, host->max_speed_hz);
+
 	clk_div = 1;
 
 	spi_engine_program_add_cmd(p, dry,
@@ -252,7 +262,7 @@ static void spi_engine_compile_message(struct spi_message *msg, bool dry,
 
 		spi_engine_gen_xfer(p, dry, xfer);
 		spi_engine_gen_sleep(p, dry, spi_delay_to_ns(&xfer->delay, xfer),
-				     xfer->effective_speed_hz);
+				     inst_ns, xfer->effective_speed_hz);
 
 		if (xfer->cs_change) {
 			if (list_is_last(&xfer->transfer_list, &msg->transfers)) {
@@ -262,7 +272,7 @@ static void spi_engine_compile_message(struct spi_message *msg, bool dry,
 					spi_engine_gen_cs(p, dry, spi, false);
 
 				spi_engine_gen_sleep(p, dry, spi_delay_to_ns(
-					&xfer->cs_change_delay, xfer),
+					&xfer->cs_change_delay, xfer), inst_ns,
 					xfer->effective_speed_hz);
 
 				if (!list_next_entry(xfer, transfer_list)->cs_off)
diff --git a/drivers/spi/spi-mux.c b/drivers/spi/spi-mux.c
index bd988f5375..031b5795d1 100644
--- a/drivers/spi/spi-mux.c
+++ b/drivers/spi/spi-mux.c
@@ -162,6 +162,7 @@ static int spi_mux_probe(struct spi_device *spi)
 	ctlr->bus_num = -1;
 	ctlr->dev.of_node = spi->dev.of_node;
 	ctlr->must_async = true;
+	ctlr->defer_optimize_message = true;
 
 	ret = devm_spi_register_controller(&spi->dev, ctlr);
 	if (ret)
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index c349d60126..9304fd03bf 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2137,7 +2137,8 @@ static void __spi_unoptimize_message(struct spi_message *msg)
  */
 static void spi_maybe_unoptimize_message(struct spi_message *msg)
 {
-	if (!msg->pre_optimized && msg->optimized)
+	if (!msg->pre_optimized && msg->optimized &&
+	    !msg->spi->controller->defer_optimize_message)
 		__spi_unoptimize_message(msg);
 }
 
@@ -4285,6 +4286,11 @@ static int __spi_optimize_message(struct spi_device *spi,
 static int spi_maybe_optimize_message(struct spi_device *spi,
 				      struct spi_message *msg)
 {
+	if (spi->controller->defer_optimize_message) {
+		msg->spi = spi;
+		return 0;
+	}
+
 	if (msg->pre_optimized)
 		return 0;
 
@@ -4315,6 +4321,13 @@ int spi_optimize_message(struct spi_device *spi, struct spi_message *msg)
 {
 	int ret;
 
+	/*
+	 * Pre-optimization is not supported and optimization is deferred e.g.
+	 * when using spi-mux.
+	 */
+	if (spi->controller->defer_optimize_message)
+		return 0;
+
 	ret = __spi_optimize_message(spi, msg);
 	if (ret)
 		return ret;
@@ -4341,6 +4354,9 @@ EXPORT_SYMBOL_GPL(spi_optimize_message);
  */
 void spi_unoptimize_message(struct spi_message *msg)
 {
+	if (msg->spi->controller->defer_optimize_message)
+		return;
+
 	__spi_unoptimize_message(msg);
 	msg->pre_optimized = false;
 }
@@ -4423,8 +4439,6 @@ int spi_async(struct spi_device *spi, struct spi_message *message)
 
 	spin_unlock_irqrestore(&ctlr->bus_lock_spinlock, flags);
 
-	spi_maybe_unoptimize_message(message);
-
 	return ret;
 }
 EXPORT_SYMBOL_GPL(spi_async);