[PATCH] spi: a3700: Set frequency limits at startup

From: Maxime Chevallier
Date: Wed Jan 17 2018 - 11:15:26 EST


Armada 3700 SPI controller has an internal clock divider which can
divide the parent clock frequency by up to 30.

This patch sets the limits in the spi_controller fields so that we can
detect when a non-supported frequency is requested by a device for a
transfer.

Signed-off-by: Maxime Chevallier <maxime.chevallier@xxxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
---
drivers/spi/spi-armada-3700.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/drivers/spi/spi-armada-3700.c b/drivers/spi/spi-armada-3700.c
index 4857b0119556..07f227e3c834 100644
--- a/drivers/spi/spi-armada-3700.c
+++ b/drivers/spi/spi-armada-3700.c
@@ -27,6 +27,8 @@

#define DRIVER_NAME "armada_3700_spi"

+#define A3700_SPI_MAX_SPEED_HZ 100000000
+#define A3700_SPI_MAX_PRESCALE 30
#define A3700_SPI_TIMEOUT 10

/* SPI Register Offest */
@@ -815,6 +817,11 @@ static int a3700_spi_probe(struct platform_device *pdev)
goto error;
}

+ master->max_speed_hz = min_t(unsigned long, A3700_SPI_MAX_SPEED_HZ,
+ clk_get_rate(spi->clk));
+ master->min_speed_hz = DIV_ROUND_UP(clk_get_rate(spi->clk),
+ A3700_SPI_MAX_PRESCALE);
+
ret = a3700_spi_init(spi);
if (ret)
goto error_clk;
--
2.15.1