[PATCH v2 1/2] spi: sun6i: Honor CS setup delay on the first transfer with native CS

[Kevin Mehall]

Move SUN6I_TFR_CTL_CS_MANUAL to sun6i_spi_set_cs.

The CS_MANUAL bit is required for CS_LEVEL to affect the CS pin state.
Set it in the same place as other CS bits to ensure that set_cs takes
effect immediately, and to make it easier to reason about CS behavior.

Previously, this bit was not set until the first transfer's
sun6i_spi_transfer_one. That meant that on the first transfer, set_cs
would have no immediate effect, and the CS falling edge was deferred
until the bit is set in transfer_one. As any configured cs_setup delay
happens between those two steps, the configured delay would have
effectively been ignored on the very first transfer. This change makes
the first transfer work like subsequent ones.

Link: https://lore.kernel.org/linux-spi/d199f72a-093b-41bb-b33e-b6685563f704@app.fastmail.com/
Fixes: 3558fe900e8a ("spi: sunxi: Add Allwinner A31 SPI controller driver")
Signed-off-by: Kevin Mehall <km at kevinmehall.net>
---
 drivers/spi/spi-sun6i.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
index 240e46f84f7b..fc228574ed38 100644
--- a/drivers/spi/spi-sun6i.c
+++ b/drivers/spi/spi-sun6i.c
@@ -185,6 +185,10 @@ static void sun6i_spi_set_cs(struct spi_device *spi, bool enable)
 	u32 reg;
 
 	reg = sun6i_spi_read(sspi, SUN6I_TFR_CTL_REG);
+
+	/* SUN6I_TFR_CTL_CS_LEVEL sets CS rather than the controller doing it automatically */
+	reg |= SUN6I_TFR_CTL_CS_MANUAL;
+
 	reg &= ~SUN6I_TFR_CTL_CS_MASK;
 	reg |= SUN6I_TFR_CTL_CS(spi_get_chipselect(spi, 0));
 
@@ -364,9 +368,6 @@ static int sun6i_spi_transfer_one(struct spi_controller *host,
 		reg |= SUN6I_TFR_CTL_DHB;
 	}
 
-	/* We want to control the chip select manually */
-	reg |= SUN6I_TFR_CTL_CS_MANUAL;
-
 	sun6i_spi_write(sspi, SUN6I_TFR_CTL_REG, reg);
 
 	if (sspi->cfg->has_clk_ctl) {
-- 
2.53.0