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

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

diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
index cd07a69e2e9355540442785f95e90823b05c9d10..44deae78913e5fa259927d1b5e8b6bf9aee60138 100644 (file)
--- 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(struct bcm2835_i2c_dev *i2c_dev, u32 reg)
 
 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(struct bcm2835_i2c_dev *i2c_dev)
 
        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;
 }