linux-kernel - [PATCH 1/3] spi: always use software fallback for SPI_CS_WORD when using cs

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Date:   Tue, 18 Sep 2018 12:08:48 -0500
From:   David Lechner <david@...hnology.com>
To:     linux-spi@...r.kernel.org, linux-iio@...r.kernel.org
Cc:     David Lechner <david@...hnology.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Mark Brown <broonie@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] spi: always use software fallback for SPI_CS_WORD when using cs_gio

This modifies the condition for using the software fallback
implementation for SPI_CS_WORD when the SPI controller is using a GPIO
for the CS line. When using a GPIO for CS, the hardware implementation
won't work, so we just enable the software fallback globally in this
case.

Signed-off-by: David Lechner <david@...hnology.com>
---
 drivers/spi/spi.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index e4fb87b304a0..03833924ca6c 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2841,11 +2841,13 @@ static int __spi_validate(struct spi_device *spi, struct spi_message *message)
 		return -EINVAL;
 
 	/* If an SPI controller does not support toggling the CS line on each
-	 * transfer (indicated by the SPI_CS_WORD flag), we can emulate it by
+	 * transfer (indicated by the SPI_CS_WORD flag) or we are using a GPIO
+	 * for the CS line, we can emulate the CS-per-word hardware function by
 	 * splitting transfers into one-word transfers and ensuring that
 	 * cs_change is set for each transfer.
 	 */
-	if ((spi->mode & SPI_CS_WORD) && !(ctlr->mode_bits & SPI_CS_WORD)) {
+	if ((spi->mode & SPI_CS_WORD) && (!(ctlr->mode_bits & SPI_CS_WORD) ||
+					  gpio_is_valid(spi->cs_gpio))) {
 		size_t maxsize;
 		int ret;
 
-- 
2.17.1