Hi Eric,
Am 02.06.2016 um 00:07 schrieb Eric Anholt:
> The register at poweron contains 0x40, which at our typical 100khz bus
> rate means .64ms instead of the desired 25ms.
>
> Fixes many clock stretching timeouts when talking to the DSI panel's
> bridge chip, and will hopefully fix talking to the FXL6408 GPIO
> expander on the Pi3 as well.
>
> Signed-off-by: Eric Anholt <eric@xxxxxxxxxx>
> ---
> drivers/i2c/busses/i2c-bcm2835.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
> index 818b051d25e6..1348f224013d 100644
> --- a/drivers/i2c/busses/i2c-bcm2835.c
> +++ b/drivers/i2c/busses/i2c-bcm2835.c
> @@ -28,6 +28,11 @@
> #define BCM2835_I2C_FIFO 0x10
> #define BCM2835_I2C_DIV 0x14
> #define BCM2835_I2C_DEL 0x18
> +/*
> + * 16-bit field for the number of SCL cycles to wait after rising SCL
> + * before deciding the slave is not responding. 0 disables the
> + * timeout detection.
> + */
> #define BCM2835_I2C_CLKT 0x1c
>
> #define BCM2835_I2C_C_READ BIT(0)
> @@ -238,6 +243,7 @@ static int bcm2835_i2c_probe(struct platform_device *pdev)
> u32 bus_clk_rate, divider;
> int ret;
> struct i2c_adapter *adap;
> + u32 clkt;
>
> i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
> if (!i2c_dev)
> @@ -280,6 +286,15 @@ static int bcm2835_i2c_probe(struct platform_device *pdev)
> }
> bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);
>
> + /*
> + * SMBUS says "Devices participating in a transfer will
> + * timeout when any clock low exceeds the value of
> + * T_TIMEOUT,MIN of 25 ms."
> + */
> + clkt = DIV_ROUND_UP(25 * bus_clk_rate, 1000);
> + clkt = min(clkt, 0xffffu);
> + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_CLKT, clkt);
> +
could we really assume that the clk rate never change after driver probing?
This also affects Gerd's patch [PATCH 28/32] i2c: bcm2835: Set up the
rising/falling edge delays.
Stefan
> irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
> if (!irq) {
> dev_err(&pdev->dev, "No IRQ resource\n");
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