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authorEric Anholt <eric@anholt.net>2018-02-08 14:54:05 +0100
committerWolfram Sang <wsa@the-dreams.de>2018-02-22 12:11:07 +0100
commitfe32a815f05c8568669a062587435e15f9345764 (patch)
treea5b50b4ce9ac7e302af1d6d852e89438831b36b3
parent15407798835a94f0936c7cbabb2f611bf20f467a (diff)
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
-rw-r--r--drivers/i2c/busses/i2c-bcm2835.c21
1 files changed, 20 insertions, 1 deletions
diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
index cd07a69e2e93..44deae78913e 100644
--- 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;
}