Patch "spi: a3700: Fix clk prescaling for coefficient over 15" has been added to the 4.14-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    spi: a3700: Fix clk prescaling for coefficient over 15

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     spi-a3700-fix-clk-prescaling-for-coefficient-over-15.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 251c201bf4f8b5bf4f1ccb4f8920eed2e1f57580 Mon Sep 17 00:00:00 2001
From: Maxime Chevallier <maxime.chevallier@smile.fr>
Date: Mon, 27 Nov 2017 15:16:32 +0100
Subject: spi: a3700: Fix clk prescaling for coefficient over 15

From: Maxime Chevallier <maxime.chevallier@smile.fr>

commit 251c201bf4f8b5bf4f1ccb4f8920eed2e1f57580 upstream.

The Armada 3700 SPI controller has 2 ranges of prescaler coefficients.
One ranging from 0 to 15 by steps of 1, and one ranging from 0 to 30 by
steps of 2.

This commit fixes the prescaler coefficients that are over 15 so that it
uses the correct range of values. The prescaling coefficient is rounded
to the upper value if it is odd.

This was tested on Espressobin with spidev and a locigal analyser.

Signed-off-by: Maxime Chevallier <maxime.chevallier@smile.fr>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/spi/spi-armada-3700.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/spi/spi-armada-3700.c
+++ b/drivers/spi/spi-armada-3700.c
@@ -79,6 +79,7 @@
 #define A3700_SPI_BYTE_LEN		BIT(5)
 #define A3700_SPI_CLK_PRESCALE		BIT(0)
 #define A3700_SPI_CLK_PRESCALE_MASK	(0x1f)
+#define A3700_SPI_CLK_EVEN_OFFS		(0x10)
 
 #define A3700_SPI_WFIFO_THRS_BIT	28
 #define A3700_SPI_RFIFO_THRS_BIT	24
@@ -220,6 +221,13 @@ static void a3700_spi_clock_set(struct a
 
 	prescale = DIV_ROUND_UP(clk_get_rate(a3700_spi->clk), speed_hz);
 
+	/* For prescaler values over 15, we can only set it by steps of 2.
+	 * Starting from A3700_SPI_CLK_EVEN_OFFS, we set values from 0 up to
+	 * 30. We only use this range from 16 to 30.
+	 */
+	if (prescale > 15)
+		prescale = A3700_SPI_CLK_EVEN_OFFS + DIV_ROUND_UP(prescale, 2);
+
 	val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
 	val = val & ~A3700_SPI_CLK_PRESCALE_MASK;
 


Patches currently in stable-queue which might be from maxime.chevallier@smile.fr are

queue-4.14/spi-a3700-fix-clk-prescaling-for-coefficient-over-15.patch