Patch "i2c: bcm2835: Set up the rising/falling edge delays" has been added to the 4.15-stable tree

[<gregkh@linuxfoundation.org>]

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

    i2c: bcm2835: Set up the rising/falling edge delays

to the 4.15-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:
     i2c-bcm2835-set-up-the-rising-falling-edge-delays.patch
and it can be found in the queue-4.15 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 fe32a815f05c8568669a062587435e15f9345764 Mon Sep 17 00:00:00 2001
From: Eric Anholt <eric@anholt.net>
Date: Thu, 8 Feb 2018 14:54:05 +0100
Subject: i2c: bcm2835: Set up the rising/falling edge delays

From: Eric Anholt <eric@anholt.net>

commit fe32a815f05c8568669a062587435e15f9345764 upstream.

We were leaving them in the power on state (or the state the firmware
had set up for some client, if we were taking over from them).  The
boot state was 30 core clocks, when we actually want to sample some
time after (to make sure that the new input bit has actually arrived).

Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/i2c/busses/i2c-bcm2835.c |   21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

--- a/drivers/i2c/busses/i2c-bcm2835.c
+++ b/drivers/i2c/busses/i2c-bcm2835.c
@@ -50,6 +50,9 @@
 #define BCM2835_I2C_S_CLKT	BIT(9)
 #define BCM2835_I2C_S_LEN	BIT(10) /* Fake bit for SW error reporting */
 
+#define BCM2835_I2C_FEDL_SHIFT	16
+#define BCM2835_I2C_REDL_SHIFT	0
+
 #define BCM2835_I2C_CDIV_MIN	0x0002
 #define BCM2835_I2C_CDIV_MAX	0xFFFE
 
@@ -81,7 +84,7 @@ static inline u32 bcm2835_i2c_readl(stru
 
 static int bcm2835_i2c_set_divider(struct bcm2835_i2c_dev *i2c_dev)
 {
-	u32 divider;
+	u32 divider, redl, fedl;
 
 	divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk),
 			       i2c_dev->bus_clk_rate);
@@ -100,6 +103,22 @@ static int bcm2835_i2c_set_divider(struc
 
 	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);
 
+	/*
+	 * Number of core clocks to wait after falling edge before
+	 * outputting the next data bit.  Note that both FEDL and REDL
+	 * can't be greater than CDIV/2.
+	 */
+	fedl = max(divider / 16, 1u);
+
+	/*
+	 * Number of core clocks to wait after rising edge before
+	 * sampling the next incoming data bit.
+	 */
+	redl = max(divider / 4, 1u);
+
+	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DEL,
+			   (fedl << BCM2835_I2C_FEDL_SHIFT) |
+			   (redl << BCM2835_I2C_REDL_SHIFT));
 	return 0;
 }
 


Patches currently in stable-queue which might be from eric@anholt.net are

queue-4.15/i2c-bcm2835-set-up-the-rising-falling-edge-delays.patch