From a2b02e4623fb127fa65a13e4ac5aa56e4ae16291 Mon Sep 17 00:00:00 2001 From: Peter Rosin Date: Mon, 25 May 2020 12:43:52 +0200 Subject: [PATCH] spi: mux: repair mux usage It is not valid to cache/short out selection of the mux. mux_control_select() only locks the mux until mux_control_deselect() is called. mux_control_deselect() may put the mux in some low power state or some other user of the mux might select it for other purposes. These things are probably not happening in the original setting where this driver was developed, but it is said to be a generic SPI mux. Also, the mux framework will short out the actual low level muxing operation when/if that is possible. Fixes: e9e40543ad5b ("spi: Add generic SPI multiplexer") Signed-off-by: Peter Rosin Link: https://lore.kernel.org/r/20200525104352.26807-1-peda@axentia.se Signed-off-by: Mark Brown --- drivers/spi/spi-mux.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/spi/spi-mux.c b/drivers/spi/spi-mux.c index 4f94c91..cc9ef37 100644 --- a/drivers/spi/spi-mux.c +++ b/drivers/spi/spi-mux.c @@ -51,6 +51,10 @@ static int spi_mux_select(struct spi_device *spi) struct spi_mux_priv *priv = spi_controller_get_devdata(spi->controller); int ret; + ret = mux_control_select(priv->mux, spi->chip_select); + if (ret) + return ret; + if (priv->current_cs == spi->chip_select) return 0; @@ -62,10 +66,6 @@ static int spi_mux_select(struct spi_device *spi) priv->spi->mode = spi->mode; priv->spi->bits_per_word = spi->bits_per_word; - ret = mux_control_select(priv->mux, spi->chip_select); - if (ret) - return ret; - priv->current_cs = spi->chip_select; return 0; -- 2.7.4