From: Marc Kleine-Budde <mkl@pengutronix.de>
To: linux-spi@vger.kernel.org, Fabio Estevam <festevam@gmail.com>,
Marek Vasut <marex@denx.de>
Cc: kernel@pengutronix.de, linux-imx@nxp.com,
Mark Brown <broonie@kernel.org>,
linux-arm-kernel@lists.infradead.org,
Baruch Siach <baruch@tkos.co.il>,
Marc Kleine-Budde <mkl@pengutronix.de>
Subject: [PATCH v1 9/9] spi: spi-imx: mx51_ecspi_prepare_message(): skip writing MX51_ECSPI_CONFIG register if unchanged
Date: Mon, 2 May 2022 19:54:57 +0200 [thread overview]
Message-ID: <20220502175457.1977983-10-mkl@pengutronix.de> (raw)
In-Reply-To: <20220502175457.1977983-1-mkl@pengutronix.de>
In mx51_ecspi_prepare_message() the MX51_ECSPI_CONFIG register is
setup for the current spi_message. After writing the register, there
is a delay to ensure that the changes hit the hardware.
This patch checks if the register MX51_ECSPI_CONFIG actually needs to
be changed. If the register content is unchanged the function is left
early, skipping the write to the hardware and the delay. This leads to
a small, but measurable performance increase. For a given workload
with small transfers on an imx6 single core the CPU load decreases
from 30% to ~27%.
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
drivers/spi/spi-imx.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index fe2305e6e38e..bc97337fddf5 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -520,6 +520,7 @@ static int mx51_ecspi_prepare_message(struct spi_imx_data *spi_imx,
u32 min_speed_hz = ~0U;
u32 testreg, delay;
u32 cfg = readl(spi_imx->base + MX51_ECSPI_CONFIG);
+ u32 current_cfg = cfg;
/* set Master or Slave mode */
if (spi_imx->slave_mode)
@@ -572,6 +573,9 @@ static int mx51_ecspi_prepare_message(struct spi_imx_data *spi_imx,
else
cfg &= ~MX51_ECSPI_CONFIG_SSBPOL(spi->chip_select);
+ if (cfg == current_cfg)
+ return 0;
+
writel(cfg, spi_imx->base + MX51_ECSPI_CONFIG);
/*
--
2.35.1
next prev parent reply other threads:[~2022-05-02 18:02 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-02 17:54 [PATCH v1 0/9] spi: spi-imx: cleanups and performance improvements Marc Kleine-Budde
2022-05-02 17:54 ` [PATCH v1 1/9] spi: spi-imx: fix sparse warning: add identifier name to function definition Marc Kleine-Budde
2022-05-02 17:54 ` [PATCH v1 2/9] spi: spi-imx: avoid unnecessary line continuations Marc Kleine-Budde
2022-05-02 17:54 ` [PATCH v1 3/9] spi: spi-imx: mx51_ecspi_intctrl(): prefer 'unsigned int' to bare use of 'unsigned' Marc Kleine-Budde
2022-05-02 17:54 ` [PATCH v1 4/9] spi: spi-imx: spi_imx_buf_rx_swap_u32(): fix sparse warning: use swab32s() instead of cpu_to_be32() Marc Kleine-Budde
2022-05-02 17:54 ` [PATCH v1 5/9] spi: spi-imx: spi_imx_buf_rx_swap_u32(): replace open coded swahw32s() Marc Kleine-Budde
2022-05-02 17:54 ` [PATCH v1 6/9] spi: spi-imx: complete conversion from master -> controller Marc Kleine-Budde
2022-05-02 17:54 ` [PATCH v1 7/9] spi: spi-imx: replace struct spi_imx_data::bitbang by pointer to struct spi_controller Marc Kleine-Budde
2022-05-02 17:54 ` [PATCH v1 8/9] spi: spi-imx: add PIO polling support Marc Kleine-Budde
2022-05-02 17:54 ` Marc Kleine-Budde [this message]
2022-05-09 21:13 ` [PATCH v1 0/9] spi: spi-imx: cleanups and performance improvements Mark Brown
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