From 3937bc239403a65b8019f473c6fce56060302ef6 Mon Sep 17 00:00:00 2001 From: David Lechner Date: Thu, 20 Jun 2024 11:43:58 -0500 Subject: [PATCH] spi: axi-spi-engine: fix sleep calculation BugLink: https://bugs.launchpad.net/bugs/2078289 [ Upstream commit 40b3d0838a1ff242e61f341e49226074bbdd319f ] The sleep calculation was not taking into account increased delay when the SPI device is not running at the maximum SCLK frequency. Rounding down when one SCLK tick was the same as the instruction execution time was fine, but it rounds down too much when SCLK is slower. This changes the rounding to round up instead while still taking into account the instruction execution time so that small delays remain accurate. Fixes: be9070bcf670 ("spi: axi-spi-engine: fix sleep ticks calculation") Signed-off-by: David Lechner Link: https://patch.msgid.link/20240620-spi-axi-spi-engine-fix-sleep-time-v1-1-b20b527924a0@baylibre.com Signed-off-by: Mark Brown Signed-off-by: Sasha Levin Signed-off-by: Portia Stephens Signed-off-by: Stefan Bader --- drivers/spi/spi-axi-spi-engine.c | 26 ++++++++++++++++++-------- 1 file changed, 18 insertions(+), 8 deletions(-) diff --git a/drivers/spi/spi-axi-spi-engine.c b/drivers/spi/spi-axi-spi-engine.c index 2b07b6dbf8a3..cdf58b1759b2 100644 --- a/drivers/spi/spi-axi-spi-engine.c +++ b/drivers/spi/spi-axi-spi-engine.c @@ -166,16 +166,20 @@ 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); @@ -222,10 +226,16 @@ 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, @@ -254,7 +264,7 @@ 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)) { @@ -264,7 +274,7 @@ 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)