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[2/4] spi: a3700: Set frequency limits at startup

Message ID 1516205728-3256-3-git-send-email-maxime.chevallier@smile.fr (mailing list archive)
State New, archived
Headers show

Commit Message

Maxime Chevallier Jan. 17, 2018, 4:15 p.m. UTC 
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@smile.fr>
---
 drivers/spi/spi-armada-3700.c | 7 +++++++
 1 file changed, 7 insertions(+)
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Patch

diff --git a/drivers/spi/spi-armada-3700.c b/drivers/spi/spi-armada-3700.c
index c11ea6c..8048468 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 */
@@ -823,6 +825,11 @@  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;