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

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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
This commit is contained in:
Eric Anholt 2018-02-08 14:54:05 +01:00 committed by Wolfram Sang
parent 1540779883
commit fe32a815f0
1 changed files with 20 additions and 1 deletions
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21
drivers/i2c/busses/i2c-bcm2835.c
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@ -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;
}